Data Sources

NOAA Climate Normals (1991-2020)

All climate data on PlainClimate comes from the U.S. Climate Normals published by NOAA's National Centers for Environmental Information (NCEI). Climate normals are 30-year averages calculated according to World Meteorological Organization standards. The current dataset covers the period 1991-2020 and was released in 2021.

Climate normals include monthly and annual averages for: temperature (mean, maximum, minimum), precipitation (total, days with measurable precipitation), snowfall (total, snow depth), heating and cooling degree days, relative humidity, dew point, and wind speed. Not all variables are available at all stations — availability depends on station equipment and data completeness.

Station Network

The NOAA station network providing climate normals includes four major types:

• Airport weather stations (USW): Operated by the National Weather Service at commercial and military airports. These provide the most comprehensive and consistent data, including temperature, precipitation, wind, humidity, and cloud cover.
• Cooperative observer stations (USC): Operated by trained volunteers who record daily temperature extremes and precipitation. The cooperative network is the oldest continuous weather observation network in the US, with some stations having records exceeding 100 years.
• Community collaborative stations (US1): Part of the Community Collaborative Rain, Hail and Snow Network (CoCoRaHS). These stations primarily record precipitation and snowfall.
• Snow telemetry stations (USS): Automated stations in mountain areas that measure snowpack depth and water equivalent. Important for western states and Alaska.

PlainClimate aggregates data from 15,492 stations to create profiles for 6,915 cities across all 50 states. When a city has multiple nearby stations, we prioritize airport stations (USW) for completeness and consistency.

What We Show vs. What We Calculate

Temperature normals, precipitation normals, snowfall totals, humidity averages, and wind speeds are taken directly from NOAA publications without modification. We do not estimate, interpolate, or adjust any climate values.

The following elements are our derived work: city-to-station mapping (linking the nearest quality station to each city), state-level summary statistics (computed from underlying city data), and the presentation format (monthly charts, comparison tables, rankings). These transformations organize the data for accessibility — they do not change the underlying values.

Accessing the Source Data

The original NOAA climate normals data is freely available at the NCEI Climate Normals portal. Individual station records can be searched using NOAA's Climate Data Online tool. Browse city and state profiles on our city search and state pages for the processed, searchable version.