This data comes from the National Centers of for Environmental Information, a division of the National Oceanic and Atmospheric Administration (NOAA). The average winter temperature is the average temperature for three months, from December to February, for each state. The year for the variable is the year that corresponds to the January and February months of the winter. For example, 2019 corresponds to the winter from December 1, 2018, to the end of February 2019. This data series does not include Hawaii (not available on the website), and data for Alaska was added from the separate dataset for Alaska’s climate data.
The information here comes from the “Climate at a Glance” webpage and is collected by the National Centers for Environmental Education at NOAA. More information about how the temperature data is gathered, collected, and synthesized can be found at Monitoring Global and U.S. Temperatures at NOAA's National Centers for Environmental Information.
The cities listed on the left below were not included in the dataset at NOAA. So listed next to each of these cities is the geographically closest city included in the dataset that was used to report the winter temperatures for the cities not included. For example, the temperatures given for Mesa are those that are reported for Phoenix.
State Data Source: NOAA National Centers for Environmental information, Climate at a Glance: Statewide Mapping, published March 2022, retrieved on April 29, 2022 from https://www.ncdc.noaa.gov/cag/.
City Data Source: NOAA National Centers for Environmental information, Climate at a Glance: City Mapping, published March 2022, retrieved on April 29, 2022 from https://www.ncdc.noaa.gov/cag/.