Weather radar is a powerful tool that provides near real-time information about the state of the atmosphere. In particular, it is able to measure the presence and amount of precipitation. For weather data consumers, radar is able to augment station-based observations with remote measurements that are able to be updated more quickly and provide information in locations without nearby stations.
This article describes how to include weather radar data into Weather API queries and Weather data downloads.
Beta Availability
Radar data features in the Timeline Weather API are currently in beta testing and open for feedback. The data is currently available for the United States and some parts of Canada. During this testing phase, the parameters, response format, and response structure may change. For more information, please contact support.
How to request precipitation information in the Weather API
Radar measurements are exposed in weather data sets and the weather API via two new weather elements: precipremote and reflectivity. In the next section, we also discuss the option to use radar-derived precipitation amounts as the value for precip element.
Example: Requesting precipremote in CSV Format
The following API request retrieves CSV-formatted precipitation data for New York, NY, USA, using the yesterday dynamic date:
https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/New%20York,%20NY/2025-02-16?key=YOUR_API_KEY&contentType=csv&include=hours&elements=datetime,precip,precipremoteIn this case, hourly data is retrieved including both the regular precip element derived from local station data and the precipremote derived from the radar source.
datetime,precip,precipremote
...
2025-02-16T05:00:00,0.037,0.039
2025-02-16T06:00:00,0.048,0.039
2025-02-16T07:00:00,0.049,0.039
...
Example: Requesting precipremote in JSON Format including current conditions, daily and hourly data
The following API request retrieves JSON-formatted precipitation data for New York, NY, USA, using the yesterday dynamic date:
https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/New%20York,%20NY/today?key=YOUR_API_KEY&contentType=JSON&elements=datetime,precip,precipremoteIn this second case, daily, hourly and current data is retrieved including both the regular precip element derived from local station data and the precipremote derived from the radar source. The current conditions also includes a radar based estimate of the precipitation in the past 60 minutes.
{
..
"days": [
{
"datetime": "2025-02-28",
"precip": 0.158,
"precipremote": 0,
"hours": [
...
{
"datetime": "17:00:00",
"precip": 0.012,
"precipremote": null
},
...
]
}
],
"currentConditions": {
"datetime": "13:08:00",
"precip": 0,
"precipremote": 0.012
}
}
Example: Adding reflectivity to the query
Reflectivity measures the intensity of the reflected signal back from the precipitation or other atmospheric interference. It measures rainfall intensity and, when precipitation is known to be rain, serves as an excellent indicator of heavy vs. light rain. It can also be used to identify different precipitation types such as rain, snow or hail.
Reflectivity is currently available in the sub-hourly data of current conditions and minute based data. To include reflectivity, include the reflectivity element:
The values of reflectivity for rainfall, typically range from 0dBZ (very weak signal often indicating rainfall that is not detectible on the ground) to more than 70dBZ which would indicate extremely intensive precipitation. While the exact range varies depending on weather system, a typical guide is:
- Low dBZ values (below 20 dBZ): Light precipitation like drizzle or light rain.
- Moderate dBZ values (20-40 dBZ): Moderate rain or snow
- High dBZ values (above 50 dBZ): Heavy rain, hail, or severe thunderstorms.
https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/44.7646,-80.6039/today?key=YOUR_API_KEY&contentType=json&include=minutes&elements=datetime,precip,reflectivity,precipremote{
...
"currentConditions": {
"datetime": "13:00:00",
"precip": 0.012,
"precipremote": 0,
"reflectivity": 30.75,
}
...
}
Using radar derived measurements rather than station observations.
In the previous examples, we have included the radar-derived precipitation estimate as a separate element, precipremote. It is possible to include the value as the value of the precip element.
When there are weather stations in the vicinity, the precip element is typically calculated by interpolating the amount of precipitation from nearby weather stations. So if there are three local stations, 15, 25 and 30 miles away, the weather data processor will calculate a weighted amount of precipitation at the requested location, weighting the closer stations more than the farther stations.
Precipitation events can be very localized, particularly in showery or thundery weather. For locations with stations that are further away, it can therefore be preferable to treat radar based precipitation as a better value for the precip element. To do this you can use the radarthreshold option in the Weather API. When this is specified, if there is no station within the specified threshold distance, radar data is used in preference.
Example: Adding a radarthreshold distance to the query
The following query sets the radar threshold to be 25000 meters (25km, 15.5miles). In this case, if there are no stations nearer than 25km, the radar precipremote amount will be included in the precip element amount.
https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/44.7646,-80.6039/today?key=YOUR_API_KEY&contentType=json&include=minutes&elements=datetime,precip,reflectivity,precipremote&options=radarthreshold_25000Summary
Integrating weather radar data into the Weather API enhances precipitation measurements by supplementing traditional station-based data with remote sensing capabilities. The key radar-based elements available in API queries are:
precipremote– Radar-derived precipitation estimates.reflectivity– Measures the intensity of reflected radar signals to help distinguish between different precipitation types and intensities.radarthreshold– Allows radar-derived precipitation to be used as the primaryprecipvalue when weather stations are unavailable within a specified distance.
By leveraging these new API features, users can obtain more accurate and location-independent precipitation data, making it particularly valuable for areas with sparse weather station coverage or rapidly changing conditions.
Questions? Contact our support team.