The U.S. Climate Normals are a large suite of data products that provide information about typical climate conditions for thousands of locations across the United States. Normals act both as a ruler to compare today’s weather and tomorrow’s forecast, and as a predictor of conditions in the near future. The official normals are calculated for a uniform 30 year period, and consist of annual/seasonal, monthly, daily, and hourly averages and statistics of temperature, precipitation, and other climatological variables from almost 15,000 U.S. weather stations.
NCEI generates the official U.S. normals every 10 years in keeping with the needs of our user community and the requirements of the World Meteorological Organization (WMO) and National Weather Service (NWS). The 1991–2020 U.S. Climate Normals are the latest in a series of decadal normals first produced in the 1950s. These data allow travelers to pack the right clothes, farmers to plant the best crop varieties, and utilities to plan for seasonal energy usage. Many other important economic decisions that are made beyond the predictive range of standard weather forecasts are either based on or influenced by climate normals.
U.S. Climate Normals Quick Access
Search for maximum, minimum, and average temperature normals and precipitation total normals for individual station locations from about 15,000 stations across the United States. Find annual/seasonal, monthly, daily, or hourly conventional 30-year normals and 15-year normals normals by station names.
U.S. Climate Normals Full Access
Search for one or multiple station locations, conventional 30-year normals and 15-year normals for all available variables and statistics. Map and text station search and selection capabilities are also available. The Data Access Tool has separate access options for both conventional 30-year (1991–2020) and supplemental 15-year (2006–2020) time periods.
Note: While older normals sets are still available through the Data Access tool, we recommend you use the current 1991–2020 release unless you have a specific use case for older versions.
Bulk Normals Download
Download CSV versions of the full suite of normals organized by variable or by station in our Web Accessible Folders for Annual/Seasonal, Monthly, Daily, and Hourly normals. More instructions and format information readme files are available in the documentation folders at these sites.
Partner Normals Access Tools
Two NOAA Regional Climate Centers partners have tools that provide unique types of access to normals products.
The RCC Custom Climatology Tool allows users to dynamically produce supplemental temperature normals for any period of time and station of interest.
Custom maps of monthly gridded normals for areas in the contiguous U.S. can be generated at the Northeast RCC.
Most of the U.S. was warmer, and the eastern two-thirds of the contiguous U.S. was wetter, from 1991–2020 than the previous normals period, 1981–2010. The Southwest was considerably drier on an annual basis, while the central northern U.S. has cooled somewhat.
There are twenty years of overlap between the current normals and the previous iteration (1991–2010), which makes the annual changes between these two datasets somewhat muted compared to trends over the same period. Monthly and seasonal changes are more dynamic. For example, the current normals for the north-central U.S. are cooler in the spring, while much of the Southeast is now warmer in October, cooler in November, and warmer again in December. Atmospheric circulation dynamics and surface feedbacks result in substantial differences from month-to-month and region-to-region.
Core Month Differences
Changes during the core months of each season (January, April, July, and October) can be representative of broader differences between different normals iterations. The following examples illustrate the percent change in precipitation and the change in degrees Fahrenheit in maximum temperature for each core month.
January temperatures have risen in the new normals by 0.5–1.5°F across most of the country. The north-central region was a notable outlier that cooled by more than 1.0° F in some places, but generally follows annual cooling patterns. Outliers aside, this winter warming correlates with increased precipitation normals throughout much of the country, as warmer air can hold more water vapor during winter. This is especially true on the western and eastern edges of the cooler north-central zone, where precipitation increased by 10–25% in January. Texas and Florida were also notably wetter during 1991–2020.
April is the most dynamic core month, and exhibits a variety of significant changes in maximum temperature and precipitation. The maximum temperature normals are considerably lower in the north-central U.S. compared to the previous normals period. The entire northern tier is cooler, but changes reach more than -2°F in parts of the Dakotas. Cooling patches reach all the way to Louisiana, although the areas to the west and east of the Mississippi Valley have warmed considerably. The entire southeastern quarter of the U.S. is now considerably wetter in April, while the southwest is drier. Additional precipitation is also seen in the lee of the northern Rocky Mountains and the Great Lakes.
The Northwest is considerably drier as a percentage of the previous normal during what is already a dry season. The rest of the West is pockmarked with wetter and drier zones. The eastern two-thirds of the U.S. has an indistinct pattern of changes in the precipitation normals. Most of the East also remained near the same temperature levels, except for persistent cooling in the north central U.S. and warming in the Northeast. However, the entire West and lee of the Rocky Mountains and Texas are all considerably (up to 2°) warmer.
A strong zonal pattern in the western two-thirds of the northern U.S. marked both wetter and cooler normals for 1991–2020 than 1981–2010. The rest of the country was consistently warmer, but the southwest and south-central U.S. were also drier. The East was warm and displayed alternating zones of wetter and drier conditions that were reminiscent of shifting storm tracks.
Overall, the central month of each season displayed cooling normals in the north-central U.S. to varying degrees, most distinctly in April. Precipitation normals were generally wetter east of the Rockies, and drier in the central and southern West. While annual normals changes were generally consistent, the single months showed pattern shifts that indicate a relationship to repeated preference of certain upper air wind patterns and storm tracks that shifted north or south with the seasons. The patterns of normals changes are following spatial trends in climate circulation dynamics and surface feedbacks, but still demonstrate the warmer conditions expected in the U.S. overall and the reduction of precipitation in the West and increase in precipitation in the East as anticipated by models of future climate change.
What are Climate Normals?
A "normal" is the 30-year average of a particular variable’s measurements, calculated for a uniform time period. Climate normals are derived from weather and climate observations captured by weather stations. The monthly minimum temperature normal in January for a given station is computed by averaging the 30 January values of monthly averaged minimum temperatures from 1991–2020 after they have been adjusted for any changes in the observing station or observing practices, and had missing months estimated from nearby more complete stations. Temperature daily normals are calculated using a procedure that ensures the daily normals for a month agree with the monthly normals when averaged. Climate Normals also include many statistics other than averages.
NOAA produces Climate Normals in accordance with the World Meteorological Organization (WMO), of which the United States is a member. The WMO requires each member nation to compute 30-year meteorological quantity averages at least every 30 years (1931–1960, 1961–1990, 1991–2020, etc.), and recommends an update each decade, in part to incorporate newer weather stations. NCEI is also responsible for fulfilling the congressional mandate "... to establish and record the climatic conditions of the United States." This stems from a provision of the Organic Act of October 1, 1890, which established the Weather Bureau as a civilian agency (15 U.S.C. 311).
In addition to basic averages for temperature, precipitation, and snowfall, more than 500 separate types of weather and climate statistics are available as part of the U.S. Normals dataset. Some are well known metrics like heating and cooling degree days, growing season length for various temperature thresholds, numbers of days with precipitation or with temperatures below freezing, etc. Other statistics are less well known, but are needed by various user communities, including percentiles and probabilities of key variables. All available variables serve a purpose, and are described in more detailed documentation available through the Data Access tool.
The science and methodologies used to generate official climate normals for the United States were well established during the creation of the 1981–2010 U.S. Climate Normals. A team of NCEI researchers spent considerable time and effort improving and automating these processes, particularly for daily and hourly normals. These methods are documented in a series of five peer-reviewed publications (Applequist et al. 2012; Arguez et al. 2012; Arguez and Applequist 2013; Durre et al. 2013; Durre and Squires 2015).
The 1991–2020 Normals calculation software was updated to incorporate feedback and recommendations from WMO Guidelines on the Calculation of Climate Normals (No. 1203) published in 2017, as well as users requests for calculation changes and new normals variables. These changes are summarized in the Normals Calculation Methodology 2020 document, along with additional technical documentation released with 1981–2010 Normals.
- Applequist, S., A. Arguez, I. Durre, M. F. Squires, R. S. Vose, and X. Yin, 2012: 1981–2010 U.S. Hourly Normals. Bulletin of the American Meteorological Society, 93, 1637-1640. doi:10.1175/BAMS-D-11-00173.1.
- Arguez, A., I. Durre, S. Applequist, R. S. Vose, M. F. Squires, X. Yin, R. R. Heim, Jr., and T. W. Owen, 2012: NOAA's 1981–2010 U.S. Climate Normals: An Overview. Bulletin of the American Meteorological Society, 93, 1687-169. doi:10.1175/BAMS-D-11-00197.1.
- Arguez, A., and S. Applequist, 2013: A Harmonic Approach for Calculating Daily Temperature Normals Constrained by Homogenized Monthly Temperature Normals. Journal of Atmospheric and Oceanic Technology, 30, 1259–1265. doi:10.1175/JTECH-D-12-00195.1.
- Durre, I., M. F. Squires, R. S. Vose, X. Yin, A. Arguez, and S. Applequist, 2012: NOAA's 1981–2010 U.S. Climate Normals: Monthly Precipitation, Snowfall, and Snow Depth. Journal of Applied Meteorology and Climatology, 52, 2377- 2395. doi:10.1175/JAMC-D-13-051.1.
- Durre, I., and M. F. Squires, 2015: White Christmas? An Application of NOAA's 1981–2010 Daily Normals. Bulletin of the American Meteorological Society, 96, 1853-1858. doi:10.1175/BAMS-D-15-00038.1.
Frequently Asked Questions
Were the 1991–2020 Climate Normals computed in the same way as 1981–2010 version?
Yes. Station normals calculations for 1991– 2020 follow the approaches pioneered in the last cycle. The Normals Calculation Methodology 2020 documentation includes references to all the detailed normals methodology publications. Some technical changes to the way normals values are rounded, percentiles calculation, and data formatting have been adopted to align with World Meteorological Organization (WMO) Guidelines on the Calculation of Climate Normals (No. 1203).
What criteria determines which stations are included in U.S. Climate Normals products?
Climate Normals are computed for as many NOAA and partner weather stations with sufficient data for 1991–2020 as reasonably possible, including those in the National Weather Services (NWS) Cooperative Observer Program (COOP) Network and the Automated Surface Observing System (ASOS) Network found at many airports. Normals are also calculated for some stations with a Weather Bureau–Army–Navy (WBAN) station identification number, including stations from the U.S. Climate Reference Network (USCRN). Finally, precipitation normals are being calculated for selected U.S. Department of Agriculture Snow Telemetry (SNOTEL) Network stations and citizen science Community Collaborative Rain, Hail, and Snow (CoCoRaHS) Network for the first time.
How many stations are included in the 1991–2020 U.S. Climate Normals?
The 1991–2020 Climate Normals includes data from more than 15,000 stations reporting precipitation and more than 7,300 stations reporting temperature. Of the stations reporting precipitation, more than 5,700 have adequate observations to report snowfall and snow depth normals. About 467 stations report hourly normals.
The 2006–2020 Climate Normals includes data from more than 13,000 stations reporting precipitation and more than 5,500 stations reporting temperature. Of the stations reporting precipitation, more than 1,600 have adequate observations to report snowfall and snow depth normals. About 1,150 stations report hourly normals.
What do climate normals tell us about global warming or climate change?
Climate Normals were not developed to track or document climate change, but instead to characterize the current climate. However, the differences between each installment do provide some evidence of climate change. This is especially apparent if current normals are compared to a long term average, such as the 1901-2000 20th Century Average often used by the NCEI Monitoring Section to compare to long time series of climate variables.
What are heating and cooling degree days? What are growing degree days?
Heating and cooling degree days are energy demand metrics associated with the variation of mean temperature across space and time. Growing degree days are climate metrics that measure the temperature inputs into agricultural systems, also as a function of mean temperature.
Degree day computations use certain threshold temperatures (e.g., 65°F for heating and cooling degree days, 50°F for growing degree days ) as base temperatures, and accumulate degree day metrics daily as departures from these baselines. Different baselines are useful for different assessments, so the Climate Normals product provides access to numerous degree day normals types with different baselines.
Does the 1991–2020 installment include Supplemental Temperature Normals?
Supplemental Temperature Normals were not developed for 1991–2020. Instead, an entire suite of 15-year normals for 2006-2020 have been calculated for all variables using the same methods used for the 30-year normals. The 15 year normals are optimized for use cases that require more recent climate information, such as predicting energy system loads and other economic decisions.
However, NCEI partners at the High Plains Regional Climate Center have developed a custom climatology tool that allows users to calculate monthly temperature normals for any time frame within the current period for the same set of stations as the conventional normals.
Do other agencies and individuals compute their own Climate Normals?
Yes. Many agencies, including the NOAA Climate Prediction Center, develop their own averages and change base periods for specific applications and/or internal use. Similarly, numerous individuals calculate their own Climate Normals for a variety of reasons. NCEI is the official source for the conventional 30-year U.S. Climate Normals.
1981–2010 U.S. Climate Normals Access Methods
Quick Access Tool
Search for temperature and precipitation Climate Normals from over 9,800 stations across the United States. Find annual, seasonal, monthly, daily, or hourly Normals by location using a map or by location and station names.
Supplemental Monthly Temperature Normals
This special product provides multiple estimates of monthly temperature normals using different definitions of the normal time period (other than 30 years) so users can make better-informed decisions tuned to their planning applications. The supplemental monthly temperature normals include 4,463 stations across the United States. Values are presented in tabular format and available as PDF files.
Use the interactive map to search for temperature and precipitation normals by station, zip code, city, county, or state as well as other normals variables, which include snowfall, heating and cooling degree days, frost and freeze dates, and growing degree days.
U.S. Climate Atlas
This tool provides access to maps of average monthly and annual minimum temperature, maximum temperature, and total precipitation. Monthly maps of minimum temperature, maximum temperature, and precipitation from 1895 through 2015 are also available, as well as map animation and comparison tools.
Download CSV/ASCII versions of the full suite of Climate Normals products from our HTTPS area.