About Our Data
All of our forecasts are generated from our proprietary forecasting system that leverages our vast amount of neighborhood weather data that we get from our community - we refer to the system as BestForecast™.
Our ever-expanding network of 100,000+ personal weather stations is the largest of its kind and provides us with a unique ability to provide the most local forecasts based on actual weather data points. BestForecast™ uses the most innovative forecast models available and cross-verifies their output with all of the localized data points. Only our unrivaled amount of local neighborhood weather data can generate forecasts for your front door.
For US locations we give users the option to switch to view the forecasts generated from the National Weather Service’s National Digital Forecast Database (NDFD). In a step to create an unprecedented level of transparency to our forecasting, we publish the recent accuracy of our forecasts for every US location alongside the accuracy of the NDFD forecasts.
What’s the Difference?
|Spatial resolution (how many forecasts within a given area)||4km grid (one forecast every 4km)--36% more forecasts than NWS||5km grid|
|Temporal resolution (how often the forecast is updated)||every 15 minutes||every 4 hours|
|Observation sources||Personal Weather Stations (quality-controlled to only include stations with accurate observations), COOPs, airport data, and weather balloon data.||Only uses COOPs, airport data, and weather balloon data|
|Forecast generation frequency||Hourly||Every 3 hours|
|Forecast length||Forecasts are generated for 14 days in the future (Weather Underground only utilizes the first 10 days on the site)||Forecasts are generated for 7 days into the future.|
Chance of Precipitation
Chance of Precipitation
|Forecast input||A variety of inputs, including, but not limited to, ECMWF, GFS, and NAM||Mostly NAM and GFS|
|Sky Conditions||Uses radar and satellite data to determine current state of sky conditions||Reports from nearest airport and other government weather stations|
|Language||Available in dozens of languages||English only|
|Worldwide coverage||Available in most countries||Forecasts are only given out for U.S. and territories.|
|Availability||BestForecast is a private forecasting system set up by some of the best meteorologists in the business, for exclusive use by The Weather Company.||Publicly available since it is coming from the U.S. Government.|
U.S. Current Conditions
U.S. current conditions data comes from 100,000+ weather stations across the country including:
- Almost 2,000 Automated Surface Observation System (ASOS) stations located at airports throughout the country. These are maintained by the Federal Aviation Administration and observations are updated hourly, or more frequently when adverse weather affecting aviation occurs (low visibility, precipitation, etc).
- Over 16,000 Personal Weather Stations (PWS's) that are part of Weather Underground's ever-expanding PWS network. Stations are put through strict quality controls and observations are updated as often as every 2.5 seconds.
- Over 26,000 weather stations that are part of the Meteorological Assimilation Data Ingest System (MADIS) which is managed by the National Oceanic and Atmospheric Administration (NOAA). For further information, see http://madis.noaa.gov/.
When a visitor requests current conditions from wunderground.com, the geographically closest station is displayed. There is also a Station Select button, which shows a list of the next closest stations.
International Current Conditions
International current conditions are collected directly from more than 29,000 weather stations located in countries around the globe including:
- About 6,000 automated weather stations operating at airports. Here is a list of the stations. Typically these stations are owned by government agencies and international airports and data is updated at 1, 3, or 6 hour intervals, depending upon the station.
- Over 8,000 Personal Weather Stations (PWS's) and 16,000 MADIS stations.
COOP Station Snow Data
The snow depth information listed by state is taken by volunteers in the National Weather Service (NWS) Cooperative Observer Program (COOP). More than 11,000 NWS-trained volunteers take observations on farms, in urban and suburban areas, National Parks, seashores, and mountaintops.
The COOP was formally created in 1890 under the Organic Act. Its mission is two-fold:
- To provide observational meteorological data, usually consisting of daily maximum and minimum temperatures, snowfall, and 24-hour precipitation totals, required to define the climate of the United States and to help measure long-term climate changes.
- To provide observational meteorological data in near real-time to support forecast, warning and other public service programs of the NWS.
For more detailed information about real-time and historical snowfall measurements from the COOP network, visit the National Climatic Data Center.
The snow depth images are taken from a dataset prepared by the United States Air Force (USAF). The data is compiled from a variety of surface and satellite-based measurements for the Northern Hemisphere. The data is updated once per day at about 7pm EST. The data has problems in many areas. In particular, it does not do well in Michigan's Upper Peninsula.
Snow data for over 600 locations in the Western U.S. mountains is available from the U.S. Department of Agriculture's SNOTEL network. These stations report snow depth, but not snowfall amount. For more detailed information about real-time and historical snowfall measurements from the SNOTEL network, visit the U.S. Department of Agriculture.