DOI: 10.3886/e233741v1
title: Climate.gov Data Snapshots: Temperature - US Monthly, Difference from Average

description: <b>Q: Was the month cooler or warmer than usual?
</b><b>
 </b><b><br></b><b>A:</b> Colors
 show where and by how much the monthly average temperature differed 
from the month’s long-term average temperature from 1991-2020. Red areas
 were warmer than the 30-year average for the month, and blue areas were
 cooler. White and very light areas had temperatures close to the 
long-term average.

 
 <br><b>Q: Where do these measurements come from?
</b><b>
 </b><b><br></b><b>A: </b>Daily
 temperature readings come from weather stations in the Global 
Historical Climatology Network (GHCN-D). Volunteer observers or 
automated instruments collect the highest and lowest temperature of the 
day at each station over the entire month, and submit them to the 
National Centers for Environmental Information (NCEI). After scientists 
check the quality of the data to omit any systematic errors, they 
calculate each station’s monthly average of daily mean temperatures, 
then plot it on a 5x5 km gridded map. To fill in the grid at locations 
without stations, a computer program interpolates (or estimates) values,
 accounting for the distribution of stations and various physical 
relationships, such as the way temperature changes with elevation. The 
resulting product is the NOAA Monthly U.S. Climate Gridded Dataset 
(NClimGrid).

To calculate the difference-from-average temperatures shown on these maps—also called temperature anomalies—NCEI
 scientists take the average temperature in each 5x5 km grid box for a 
single month and year, and subtract its 1991-2020 average for the same 
month. If the result is a positive number, the region was warmer than 
average. A negative result means the region was cooler than usual.

 
 <br><b>Q: What do the colors mean?</b><b>
 </b><br><b>A: </b>Shades
 of blue show places where average monthly temperatures were below their
 long-term average for the month. Areas shown in shades of pink to red 
had average temperatures that were warmer than usual. The darker the 
shade of red or blue, the larger the difference from the long-term 
average temperature. White and very light areas show where average 
monthly temperature was the same as or very close to the long-term 
average.

 
 <br><b>Q: Why do these data matter?</b><b>
 </b><br><b>A:</b> Comparing
 an area’s recent temperature to its long-term average can tell how warm
 or how cool the area is compared to usual. Temperature anomalies also 
give us a frame of reference to better compare locations. For example, 
two areas might have each had recent temperatures near 70°F, but 70°F 
could be above average for one location while below average for another.
 Knowing an area is much warmer or much cooler than usual can encourage 
people to pay close attention to on-the-ground conditions that affect 
daily life and decisions. People check maps like this to judge crop 
progress, estimate energy use, consider snow and lake ice melt; and to 
understand impacts on wildfire regimes.

 
 <br><b>Q: How did you produce these snapshots?</b><b>
 </b><br><b>A: </b>Data
 Snapshots are derivatives of existing data products: to meet the needs 
of a broad audience, we present the source data in a simplified visual 
style. This set of snapshots is based on NClimGrid climate data produced
 by and available from the National Centers for Environmental 
Information (NCEI). To produce our images, we invoke a set of scripts 
that access the source data and represent them according to our selected
 color ramps on our base maps.

 
 <br><b>Q: Data Format Description</b><b>
 </b><br><b>A: </b>NetCDF (Version: 4)

 
 Additional information
 The data used
 in these snapshots can be downloaded from different places and in 
different formats. We used these specific data sources:

NClimGrid Average Temperature<br>
NClimGrid Temperature Normals

 
 <br><b>References</b>
 
 NOAA Monthly U.S. Climate Gridded Dataset (NClimGrid)<br>
NOAA Monthly U.S. Climate Divisional Database (NClimDiv)<br>
Improved Historical Temperature and Precipitation Time Series for U.S. Climate Divisions<br>
NCEI Monthly National Analysis<br>
Climate at a Glance - Data Information<br>
NCEI Climate Monitoring - All Products
 <br>Source: https://www.climate.gov/maps-data/data-snapshots/data-source/temperature-us-monthly-difference-avera...<br>This upload includes two additional files:<br>*Temperature - US Monthly, Difference from Average _NOAA Climate.gov.pdf is a screenshot of the main Climate.gov site for these snapshots (https://www.climate.gov/maps-data/data-snapshots/data-source/temperature-us-monthly-difference-avera...)<br>* Cimate_gov_ Data Snapshots.pdf is a screenshot of the data download page for the full-resolution files. (https://www.climate.gov/data/Temperature--Monthly--Difference-from-average--CONUS/04-full_res_zips/)<br><br><br><br>
description: Data is divided in to folders by image resolution -- full size (zip), small (png), and large (png). Occasionally there may be one image missing in a particular size but available in another size.<br><br>Data downloaded from climate.gov <br>full resolution files: 6/14/2025; <br>small, large files: 6/21/2025<br><br>