Core Data Fields
Core Data Fields
FreeThis page provides a reference of the core data fields available through the Tomorrow.io Weather API, including their descriptions, units, data types, availability, and common use cases.
All core data fields listed on this page are available for free to all users.
Core Data Fields Reference
Use the table below to find detailed information about the core weather data fields available in the API. You can reference these field names in your API requests using the fields parameter.
| Data Field | Description | Values/Units | Data Type | Example | Common Use Cases | Query Parameter | Availability | Interfaces | Related Fields |
|---|---|---|---|---|---|---|---|---|---|
| Temperature Metrics | |||||||||
temperature | The "real" temperature measurement at 2m above ground | Metric: Celsius [-90,60] Imperial: Fahrenheit [-130,140] | Number | 64.5 | Daily forecasts, clothing recommendations, HVAC control systems, health warnings | fields=temperature | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | temperatureApparent, temperatureMin, temperatureMax, dewPoint |
temperatureApparent | The temperature equivalent perceived by humans ("feels like"), caused by combined effects of air temperature, humidity, and wind speed | Metric: Celsius [-90,60] Imperial: Fahrenheit [-130,140] | Number | 62.6 | Outdoor activity planning, safety warnings, user-facing weather displays | fields=temperatureApparent | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | temperature, humidity, windSpeed |
temperatureMin | Minimum temperature over the interval period | Metric: Celsius [-90,60] Imperial: Fahrenheit [-130,140] | Number | 54.5 | Daily forecast summaries, agriculture planning, cold weather warnings | fields=temperatureMin (daily timesteps only) | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | temperature, temperatureMax |
temperatureMax | Maximum temperature over the interval period | Metric: Celsius [-90,60] Imperial: Fahrenheit [-130,140] | Number | 72.7 | Daily forecast summaries, heat warnings, outdoor event planning | fields=temperatureMax (daily timesteps only) | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | temperature, temperatureMin |
dewPoint | The temperature to which air must be cooled to become saturated with water vapor (at 2m) | Metric: Celsius [0,100] Imperial: Fahrenheit [32,212] | Number | 43.8 | Comfort indices, fog prediction, agriculture (frost risk), HVAC efficiency | fields=dewPoint | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | temperature, humidity |
| Humidity Metrics | |||||||||
humidity | The concentration of water vapor present in the air | % | Number | 66 | Comfort indices, health warnings, agriculture, construction scheduling | fields=humidity | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | dewPoint, temperatureApparent |
| Wind Metrics | |||||||||
windSpeed | The fundamental atmospheric quantity caused by air moving from high to low pressure (at 10m) | Metric: m/s Imperial: mph | Number | 4.2 | Transportation safety, outdoor activities, wind power forecasting, maritime operations | fields=windSpeed | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | windDirection, windGust, temperatureApparent |
windDirection | The direction from which wind originates, measured in degrees clockwise from due north (at 10m) | degrees or null | Number | 104 | Navigation, wildfire spread prediction, airport operations, pollution dispersal | fields=windDirection | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | windSpeed, windGust |
windGust | The maximum brief increase in wind speed, usually less than 20 seconds (at 10m) | Metric: m/s Imperial: mph | Number | 12.3 | Safety warnings, construction operations, event planning, aviation | fields=windGust | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | windSpeed, windDirection |
| Pressure Metrics | |||||||||
pressureSurfaceLevel | The force exerted against a surface by the weight of air above the surface (at surface level) | Metric: hPa Imperial: inHg | Number | 29.82 | Altimeter calibration, weather system tracking, barometric pressure monitoring | fields=pressureSurfaceLevel | [-6h to +15d] | Timeline (T), Insights (I), Route (R) | pressureSeaLevel |
pressureSeaLevel | The force exerted against a surface by the weight of air above the surface (at mean sea level) | Metric: hPa Imperial: inHg | Number | 30.07 | Weather pattern forecasting, storm prediction, aviation safety, meteorological research | fields=pressureSeaLevel | [-6h to +15d] | Timeline (T), Map (M), Route (R) | pressureSurfaceLevel |
| Precipitation Metrics | |||||||||
precipitationIntensity | The instantaneous precipitation rate at ground level | Metric: mm/hr Imperial: in/hr | Number | 0.02 | Flood warnings, transportation safety, outdoor event planning, agriculture | fields=precipitationIntensity | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | precipitationType, rainIntensity, snowIntensity, sleetIntensity, freezingRainIntensity |
precipitationProbability | Probability of precipitation (>0.0254 cm) | % | Number | 5 | Trip planning, outdoor event scheduling, umbrella alerts, clothing recommendations | fields=precipitationProbability | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | precipitationIntensity, weatherCode |
precipitationType | The type of precipitation falling to ground level | 1: Rain 2: Snow 3: Freezing Rain 4: Ice Pellets/Sleet | Integer | 1 | Road condition warnings, aviation operations, outdoor event planning, clothing recommendations | fields=precipitationType | [-6h to +15d] | Timeline (T), Insights (I), Route (R) | precipitationIntensity, weatherCode |
rainIntensity | The measure of the intensity of rainfall | Metric: mm/hr Imperial: in/hr | Number | 0.01 | Flood warnings, agricultural planning, stormwater management, event planning | fields=rainIntensity | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | precipitationIntensity, precipitationType, rainAccumulation |
rainAccumulation | The accumulated amount of liquid rain for the past or future hour of the requested time | Metric: mm Imperial: in | Number | 0.04 | Flood risk assessment, reservoir management, agriculture, construction planning | fields=rainAccumulation | [-6h to +15d] | Timeline (T), Insights (I) | rainIntensity, precipitationIntensity |
snowIntensity | The measure of the intensity of snowfall | Metric: mm/hr Imperial: in/hr | Number | 0 | Road safety warnings, snow removal planning, school closures, ski resort operations | fields=snowIntensity | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | precipitationIntensity, precipitationType, snowAccumulation |
snowAccumulation | The accumulated amount of new snowfall for the past or future hour of the requested time | Metric: mm Imperial: in | Number | 0 | Road clearing operations, snow load calculations, school closures, winter sports planning | fields=snowAccumulation | [-6h to +15d] | Timeline (T), Insights (I) | snowIntensity, snowAccumulationLwe |
snowAccumulationLwe | The accumulated amount of new snowfall expressed as liquid water equivalent | Metric: mm Imperial: in | Number | 0 | Water resource management, flood risk assessment, hydrological modeling | fields=snowAccumulationLwe | [-6h to +15d] | Timeline (T), Insights (I) | snowAccumulation, snowIntensity |
sleetIntensity | The measure of the intensity of sleet (ice pellets) | Metric: mm/hr Imperial: in/hr | Number | 0 | Road safety warnings, transportation planning, winter weather alerts | fields=sleetIntensity | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | precipitationIntensity, precipitationType, sleetAccumulation |
sleetAccumulation | The accumulated amount of sleet for the past or future hour of the requested time | Metric: mm Imperial: in | Number | 0 | Road condition monitoring, ice accumulation warnings, winter maintenance planning | fields=sleetAccumulation | [-6h to +15d] | Timeline (T), Insights (I) | sleetIntensity, precipitationIntensity |
freezingRainIntensity | The measure of the intensity of freezing rain | Metric: mm/hr Imperial: in/hr | Number | 0 | Ice storm warnings, power outage predictions, transportation safety, aviation hazards | fields=freezingRainIntensity | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | precipitationIntensity, precipitationType, freezingRainAccumulation |
freezingRainAccumulation | The accumulated amount of freezing rain for the past or future hour of the requested time | Metric: mm Imperial: in | Number | 0 | Ice load calculations, infrastructure damage assessment, emergency response planning | fields=freezingRainAccumulation | [-6h to +15d] | Timeline (T), Insights (I) | freezingRainIntensity, precipitationIntensity |
iceAccumulation | The accumulated amount of ice for the past or future hour of the requested time | Metric: mm Imperial: in | Number | 0 | Ice storm impact assessment, power line safety, structural load calculations | fields=iceAccumulation | [-6h to +15d] | Timeline (T), Insights (I) | iceAccumulationLwe, freezingRainAccumulation |
iceAccumulationLwe | The accumulated amount of ice expressed as liquid water equivalent | Metric: mm Imperial: in | Number | 0 | Hydrological modeling, water resource management, flood risk assessment | fields=iceAccumulationLwe | [-6h to +15d] | Timeline (T), Insights (I) | iceAccumulation, freezingRainAccumulation |
snowDepth | The depth of snow on the ground | Metric: mm Imperial: in | Number | 0 | Snow removal planning, recreational activities, structural load assessment, avalanche risk | fields=snowDepth | [-6h to +15d] | Timeline (T), Insights (I) | snowAccumulation, snowIntensity |
| Visibility & Cloud Metrics | |||||||||
visibility | The measure of the distance at which an object or light can be clearly discerned | Metric: km Imperial: mi | Number | 9.94 | Transportation safety, airport operations, maritime navigation, fog warnings | fields=visibility | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | cloudCover, weatherCode, precipitationIntensity |
cloudCover | The fraction of the sky obscured by clouds when observed from a particular location | % | Number | 28 | Solar energy predictions, photography planning, outdoor activity planning | fields=cloudCover | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | weatherCode, visibility, uvIndex |
cloudBase | The lowest altitude of the visible portion of a cloud (above ground level) | Metric: km or null Imperial: mi or null | Number | 0.6 | Aviation safety, pilot briefings, aircraft operations, meteorological analysis | fields=cloudBase | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | cloudCover, cloudCeiling, visibility |
cloudCeiling | The highest altitude of the visible portion of a cloud (above ground level) | Metric: km or null Imperial: mi or null | Number | 0.2 | Aviation safety, flight planning, weather analysis, airport operations | fields=cloudCeiling | [-6h to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | cloudCover, cloudBase, visibility |
| Solar & Astronomy Metrics | |||||||||
sunriseTime | The daily appearance of the Sun on the horizon due to Earth's rotation | UTC ISO-8601 | String | "2025-05-12T04:23:00Z" | Outdoor lighting planning, solar energy systems, nature photography, hunting/fishing | fields=sunriseTime | [-6h to +15d] | Timeline (T), Insights (I) | sunsetTime, uvIndex |
sunsetTime | The daily disappearance of the Sun below the horizon due to Earth's rotation | UTC ISO-8601 | String | "2025-05-12T19:29:00Z" | Outdoor lighting planning, solar energy systems, nature photography, hunting/fishing | fields=sunsetTime | [-6h to +15d] | Timeline (T), Insights (I) | sunriseTime, uvIndex |
moonPhase | The shape of the directly sunlit portion of the Moon as viewed from Earth | 0: New 1: Waxing Crescent 2: First Quarter 3: Waxing Gibbous 4: Full 5: Waning Gibbous 6: Third Quarter 7: Waning Crescent | Integer | 4 | Night photography, astronomical observations, cultural events, fishing schedules | fields=moonPhase | [-6h to +15d] | Timeline (T) | moonriseTime, moonsetTime |
moonriseTime | The time at which the moon rises above the horizon | UTC ISO-8601 | String | "2025-05-12T20:05:12Z" | Night photography, astronomical observations, fishing schedules, tidal predictions | fields=moonriseTime | [-6h to +15d] | Timeline (T), Insights (I) | moonsetTime, moonPhase |
moonsetTime | The time at which the moon sets below the horizon | UTC ISO-8601 | String | "2025-05-12T03:39:23Z" | Night photography, astronomical observations, fishing schedules, tidal predictions | fields=moonsetTime | [-6h to +15d] | Timeline (T), Insights (I) | moonriseTime, moonPhase |
| UV & Health Metrics | |||||||||
uvIndex | Standard measurement of the strength of sunburn producing UV radiation | 0-2: Low 3-5: Moderate 6-7: High 8-10: Very High 11+: Extreme | Integer | 5 | Health warnings, sun protection advice, outdoor activity scheduling | fields=uvIndex | [-6h to +108h] | Timeline (T) | uvHealthConcern, cloudCover |
uvHealthConcern | Health concern level based on UV index ranges | 0-2: Low 3-5: Moderate 6-7: High 8-10: Very High 11+: Extreme | Integer | 2 | Health apps, sun protection alerts, outdoor safety recommendations, skin care advice | fields=uvHealthConcern | [-6h to +108h] | Timeline (T) | uvIndex, cloudCover |
| Weather Code Metrics | |||||||||
weatherCode | The text description that conveys the most prominent weather condition | 1000: Clear 1001: Cloudy 1100: Mostly Clear 1101: Partly Cloudy 1102: Mostly Cloudy 2000: Fog 4000: Drizzle 4001: Rain 4200: Light Rain 4201: Heavy Rain 5000: Snow 5001: Flurries 5100: Light Snow 5101: Heavy Snow 6000: Freezing Drizzle 6001: Freezing Rain 7000: Ice Pellets 7101: Heavy Ice Pellets 8000: Thunderstorm | Integer | 1000 | Weather displays, icon selection, activity recommendations, alerts | fields=weatherCode | [-6h to +15d] | Timeline (T), Route (R) | precipitationType, cloudCover, precipitationIntensity |
weatherCodeFullDay | The most prominent weather condition during the day (from sunrise till next sunrise) | Same codes as weatherCode | Integer | 1100 | Daily weather summaries, full-day planning, weather app displays, daily forecasts | fields=weatherCodeFullDay | [-6h to +15d] | Timeline (T), Route (R) | weatherCode, sunriseTime, sunsetTime |
weatherCodeDay | The most prominent weather condition during the day (from sunrise till sunset) | Same codes as weatherCode | Integer | 1000 | Daytime activity planning, solar energy forecasting, outdoor event scheduling | fields=weatherCodeDay | [-6h to +15d] | Timeline (T), Route (R) | weatherCode, weatherCodeNight, sunriseTime, sunsetTime |
weatherCodeNight | The most prominent weather condition during the night (from sunset till sunrise) | Same codes as weatherCode | Integer | 1001 | Nighttime activity planning, astronomical observations, overnight operations | fields=weatherCodeNight | [-6h to +15d] | Timeline (T), Route (R) | weatherCode, weatherCodeDay, sunriseTime, sunsetTime |
| Specialized Metrics | |||||||||
evapotranspiration | The combined processes by which water moves from the earth's surface into the atmosphere (Penman–Monteith FAO56) | Metric: mm Imperial: in | Number | 0.009 | Agricultural irrigation planning, water resource management, crop yield prediction, drought monitoring | fields=evapotranspiration | [-6h to +15d] | Timeline (T), Insights (I) | temperature, humidity, windSpeed, precipitationIntensity |
ezHeatStressIndex | Heat stress index based on Ezra-Zohar formula | 0-22: No Heat Stress 22-24: Mild Heat Stress 24-26: Moderate Heat Stress 26-28: Medium Heat Stress 28-30: Severe Heat Stress 30+: Extreme Heat Stress | Number | 25 | Worker safety, outdoor event planning, health warnings, sports scheduling, construction safety | fields=ezHeatStressIndex | [-7d to +15d] | Timeline (T), Insights (I), Map (M), Route (R) | temperature, temperatureApparent, humidity, windSpeed |
thunderstormProbability | The probability that lightning flash density exceeds 0.1 with units of (100 km^2 / hour) | % | Number | 15 | Severe weather warnings, outdoor event planning, aviation safety, lightning protection | fields=thunderstormProbability | [+14d] | Timeline (T), Insights (I), Map (M) | weatherCode, precipitationIntensity, windGust |
| Growing Degree Days (Agricultural) | |||||||||
gdd10To30 | Growing Degree Days calculation with a temperature base of 10°C and a temperature cap of 30°C. Typically used to determine Maize and Soybean phonological stage | Growing degree days | Number | 12.5 | Maize and soybean crop development tracking, agricultural planning, harvest timing | fields=gdd10To30 | [-6h to +15d] | Timeline (T), Route (R) | temperature, temperatureMin, temperatureMax |
gdd10To31 | Growing Degree Days calculation with a temperature base of 10°C and a temperature cap of 31°C. Typically used to determine Sunflower phonological stage | Growing degree days | Number | 13.2 | Sunflower crop development tracking, agricultural planning, harvest timing | fields=gdd10To31 | [-6h to +15d] | Timeline (T), Route (R) | temperature, temperatureMin, temperatureMax |
gdd08To30 | Growing Degree Days calculation with a temperature base of 8°C and a temperature cap of 30°C. Typically used to determine Green Gram and Sorghum phonological stage | Growing degree days | Number | 14.8 | Green gram and sorghum crop development tracking, agricultural planning, harvest timing | fields=gdd08To30 | [-6h to +15d] | Timeline (T), Route (R) | temperature, temperatureMin, temperatureMax |
gdd03To25 | Growing Degree Days calculation with a temperature base of 3°C and a temperature cap of 25°C. Typically used to determine Potatoes phonological stage | Growing degree days | Number | 16.2 | Potato crop development tracking, agricultural planning, harvest timing | fields=gdd03To25 | [-6h to +15d] | Timeline (T), Route (R) | temperature, temperatureMin, temperatureMax |
| Soil Metrics | |||||||||
soilMoistureVolumetric0To10 | Soil moisture in the top 0-10cm layer expressed as volumetric water content | m³/m³ | Number | 0.25 | Precision agriculture, irrigation scheduling, drought monitoring, crop health assessment | fields=soilMoistureVolumetric0To10 | [-6h to +15d] | Timeline (T), Insights (I) | soilMoistureVolumetric10To40, precipitationIntensity, evapotranspiration |
soilMoistureVolumetric10To40 | Soil moisture in the 10-40cm layer expressed as volumetric water content | m³/m³ | Number | 0.28 | Root zone monitoring, irrigation planning, agricultural decision making | fields=soilMoistureVolumetric10To40 | [-6h to +15d] | Timeline (T), Insights (I) | soilMoistureVolumetric0To10, soilMoistureVolumetric40To100 |
soilMoistureVolumetric40To100 | Soil moisture in the 40-100cm layer expressed as volumetric water content | m³/m³ | Number | 0.32 | Deep root zone monitoring, long-term agricultural planning, drought assessment | fields=soilMoistureVolumetric40To100 | [-6h to +15d] | Timeline (T), Insights (I) | soilMoistureVolumetric10To40, soilMoistureVolumetric100To200 |
soilMoistureVolumetric100To200 | Soil moisture in the 100-200cm layer expressed as volumetric water content | m³/m³ | Number | 0.35 | Groundwater monitoring, deep agricultural planning, hydrological modeling | fields=soilMoistureVolumetric100To200 | [-6h to +15d] | Timeline (T), Insights (I) | soilMoistureVolumetric40To100, precipitationIntensity |
soilTemperature0To10 | Soil temperature in the top 0-10cm layer | Metric: Celsius Imperial: Fahrenheit | Number | 18.5 | Seed germination timing, planting decisions, agricultural planning | fields=soilTemperature0To10 | [-6h to +15d] | Timeline (T), Insights (I) | temperature, soilTemperature10To40 |
soilTemperature10To40 | Soil temperature in the 10-40cm layer | Metric: Celsius Imperial: Fahrenheit | Number | 17.8 | Root zone temperature monitoring, agricultural planning, crop development | fields=soilTemperature10To40 | [-6h to +15d] | Timeline (T), Insights (I) | soilTemperature0To10, soilTemperature40To100 |
soilTemperature40To100 | Soil temperature in the 40-100cm layer | Metric: Celsius Imperial: Fahrenheit | Number | 16.2 | Deep root zone monitoring, long-term agricultural planning, geothermal applications | fields=soilTemperature40To100 | [-6h to +15d] | Timeline (T), Insights (I) | soilTemperature10To40, soilTemperature100To200 |
soilTemperature100To200 | Soil temperature in the 100-200cm layer | Metric: Celsius Imperial: Fahrenheit | Number | 15.5 | Groundwater temperature monitoring, geothermal applications, climate research | fields=soilTemperature100To200 | [-6h to +15d] | Timeline (T), Insights (I) | soilTemperature40To100, temperature |