Data Sources
myPerfectWeather.com uses data from the National Center for Environmental Information, with 15,000+ weather stations across the USA reporting precipitation, snowfall, humidity and temperature. The data is collected and processed over a 30-year period from 1991-2020, ensuring accuracy. A sophisticated algorithm identifies nearby weather stations for each city and calculates weather data based on a weighted average of station data, ensuring accuracy and relevance. We also source population information from the US Census database and use industry-leading technology from © OpenStreetMap and Leaflet to power our maps. With these powerful tools, you can easily visualize and explore weather patterns in your area with confidence and accuracy.
The GHI and DNI data come from the U.S. National Laboratory of the Rockies, formerly the National Renewable Energy Laboratory (NREL), which uses its Physical Solar Model (PSM)
together with satellite observations from the GOES weather satellites. The model first calculates the theoretical amount of
solar radiation based on the Sun’s position for a given location and time. It then adjusts those values using satellite
measurements of real-world conditions — such as clouds, haze, smoke, and aerosols — that block or scatter sunlight.
To highlight reliable patterns rather than day-to-day weather noise, the results are averaged over many years.
Sunshine hours (or Sunshine duration) per day are estimated by counting the time when direct sunlight
(measured as Direct Normal Irradiance, or DNI) exceeds 120 W/m²,
following the World Meteorological Organization standard. Sunshine hours are calculated only during daylight
and are averaged over many years to capture long-term patterns.
Climate data shown on the map is currently at the county level for performance reasons. In geographically diverse regions (such as San Diego County), this may not accurately reflect conditions in specific cities or neighborhoods.