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1981-2010 U.S. Climate Normals

The 1981–2010 Climate Normals are NCDC's latest three-decade averages of climatological variables, including temperature and precipitation. This product replaces the 1971–2000 Climate Normals product, which remains available as historical data.

Data Access

  • Search Tool
    Search for temperature and precipitation Climate Normals for over 9,800 stations across the United States. Select from tabs and drop-down menus to view monthly, daily, annual, seasonal, or hourly Normals by location, station, and date.
  • Interactive Map
    Select locations on the interactive map by station, zip code, city, county, or state for temperature and precipitation Normals as well as supplemental Normals, which include snowfall, heating and cooling degree days, frost and freeze dates, and growing degree days.
  • FTP
    Download ASCII versions of the full suite of Climate Normals products from our FTP area. This type of access is for individuals who have experience with FTP and programming languages. We recommend that you review the readme.txt file prior to downloading the data as it describes all file information and locations.
  • HTTP
    Download ASCII versions of the full suite of Climate Normals products from our HTTP area rather than the FTP area as described above.

FAQs

What are Climate Normals?

In the strictest sense, a "normal" of a particular variable (e.g., temperature) is defined as the 30-year average. For example, the minimum temperature normal in January for a station in Chicago, Illinois, would be computed by taking the average of the 30 January values of monthly averaged minimum temperatures from 1981 to 2010. Each of the 30 monthly values was in turn derived from averaging the daily observations of minimum temperature for the station. In practice, however, much more goes into NCDC's Climate Normals product than simple 30-year averages. Procedures are put in place to deal with missing and suspect data values. In addition, Climate Normals include quantities other than averages such as degree days, probabilities, standard deviations, etc. Climate Normals are a large suite of data products that provide users with many tools to understand typical climate conditions for thousands of locations across the United States.

Why does NOAA produce Climate Normals?

NOAA's computation of Climate Normals is in accordance with the recommendation of the World Meteorological Organization (WMO), of which the United States is a member. While the WMO mandates each member nation to compute 30-year averages of meteorological quantities at least every 30 years (1931–1960, 1961–1990, 1991–2020, etc.), the WMO recommends a decadal update, in part to incorporate newer weather stations. Further, NOAA's NCDC has a responsibility to fulfill the mandate of Congress "... to establish and record the climatic conditions of the United States." This responsibility 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).

What are Climate Normals used for?

Meteorologists and climatologists regularly use Climate Normals for placing recent climate conditions into a historical context. NOAA's Climate Normals are commonly seen on local weather news segments for comparisons with the day's weather conditions. In addition to weather and climate comparisons, Climate Normals are utilized in seemingly countless applications across a variety of sectors. These include regulation of power companies, energy load forecasting, crop selection and planting times, construction planning, building design, and many others.

Were the 1981–2010 Climate Normals computed in the same way as previous versions?

No. Several changes and additions have been incorporated into the 1981–2010 Climate Normals. For a detailed overview of these changes and additions, please consult Arguez et al. (2012) for daily and monthly normals and Applequist et al. (2012) for hourly normals.

What qualifies or disqualifies a station to be included in Climate Normals products?

Climate Normals are computed for as many stations operated by the National Weather Service (NWS) as reasonably possible. Some stations do not have sufficient data over the 1981–2010 period to be included in the Climate Normals, and this is the primary reason a station may not be included. Climate Normals are computed for stations that are part of the NWS Cooperative Observer Program (COOP) Network. Some additional stations are included that have a Weather Bureau–Army–Navy (WBAN) station identification number including the U.S. Climate Reference Network (USCRN). Climate Normals are only computed for stations in the United States (including Alaska and Hawaii) as well as U.S. territories, commonwealths, compact of free association nations, and one Canadian USCRN station.

How many stations are included in the Climate Normals?

The 1981–2010 Climate Normals includes normals for over 9,800 stations. Temperature-related normals are reported for 7,500 stations and precipitation normals are provided for 9,300 stations, including 6,400 that also have snowfall normals and 5,300 that have normals of snow depth. Hourly Climate Normals are available for 262 stations.

What do Climate Normals tell us about global warming or climate change?

Climate Normals were not designed to be metrics of climate change. In fact, when the widespread practice of computing Climate Normals commenced in the 1930s, the generally accepted notion of the climate was that underlying long-term averages of climate time series were constant. Changes from one installment of Climate Normals to the next do, nonetheless, provide some evidence of climate change impacts. However, care must be taken when interpreting changes between one Climate Normals period and the other. Differences between the reported 1971–2000 Climate Normals and the 1981–2010 Climate Normals may be due to station moves, changes in methodology, changes in instrumentation, etc., that are not reflective of real changes in the underlying climate signal. Rather than inferring Climate Change impacts from Climate Normals, we recommend users instead look at trends in U.S. Historical Climatology Network (USHCN) time series.

What portion of the difference from the new Climate Normals and the previous Climate Normals was due to climate change?

Compared to the previous Climate Normals, the new Climate Normals includes the decade of the 2000s and loses the decade of the 1970s. As the 2000s were warmer than the 1970s, this has had a warming influence on the Climate Normals. Comparing these decades using our best dataset for climate change analysis, the USHCN, we find that the decade of the 2000s was about 1.5°F warmer than the 1970s. For maximum, minimum, and mean temperature the difference, respectively, was 1.37°F, 1.55°F, and 1.46°F. As the Climate Normals are an average of three decades, this warmed the new Climate Normals by approximately 0.5°F. The difference between these values and the actual difference between the reported 1971–2000 Normals and the new Normals are caused by station moves, changes in observing practices or instruments, etc.

What are heating and cooling degree days? What are growing degree days?

Heating and cooling degree days are metrics of energy demand associated with the variation of mean temperature across space and time. Growing degree days are metrics of agricultural output, also as a function of mean temperature. The computation of degree days involves certain threshold temperatures, e.g., 65°F for heating and cooling degree days. These thresholds are referred to as base temperatures.

How can I obtain heating and cooling degree day Normals set to different base temperatures? And for growing degree units?

While NCDC utilizes 65°F as the base temperature for the standard calculation of heating and cooling degree days, the Climate Normals products include alternative computations of heating and cooling degree days for various base temperatures. In addition, growing degree days are computed for various crop-specific base temperatures. These Climate Normals products can be obtained using any of the access mechanisms described above.

How can I obtain Climate Normals for other weather elements such as dew point temperature, sea level pressure, and wind?

The vast majority of weather stations utilized in the 1981–2010 Climate Normals only routinely report air temperature and precipitation. A smaller set of stations have fairly complete records of additional variables such as dew point temperature, sea level pressure, and wind speed and direction. For 262 first order stations, we provide hourly normals of temperature, dew point temperature, heat index, wind chill, heating and cooling degree hours, sea level pressure, and wind.

How does the transition to ASOS affect the computation of Climate Normals?

Automated Surface Observing System (ASOS) stations were implemented in the mid-1990s. As a result, there are inhomogeneities in the 1981–2010 underlying data records due to changes in observing practices. These inhomogeneities are accounted for to the extent possible by quality control and the standardization of monthly temperature values. See Menne et al. (2009) and Menne and Williams (2009) for more information.

How do the 1981–2010 Climate Normals compare to Alternative Normals and Dynamic Normals?

In response to observed Climate Change, NOAA's NCDC has been investigating a suite of products that attempt to provide a better estimate of "normal" than the traditional 30-year average Climate Normals of temperature. This project was previously known as Alternative Normals. Currently, NCDC plans to include some of the alternatives as part of the 1981–2010 Climate Normals suite of products, in response to feedback received at an April 2012 workshop on this topic. Dynamic Normals refers to a legacy tool available on NCDC's website that allowed users to create their own Climate Normals for a particular station by selecting customized start and end years for the averages. This tool has not been updated since 2001 and there are no plans to update this tool in the foreseeable future.

Do other agencies and individuals compute their own Climate Normals?

Yes. Many agencies, including NOAA's 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. In contrast with many non-official computations of climatological means from a myriad of sources, NCDC is the official source for calculations of U.S. Climate Normals. This official status is in keeping with NCDC's monitoring and reporting responsibilities.

Where can I find more information about the 1981–2010 Climate Normals and how they were computed?

A number of documents are available that provide information about the new Climate Normals and explain in technical terms how they were computed. Please see the References section below.

References

  • For a broad overview of NOAA's 1981–2010 Climate Normals, see:

    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, 1687-1697. PDF

  • For a detailed description of precipitation, snowfall, and snow depth Normals, see:

    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, Submitted. PDF

    Durre, I., M. F. Squires, R. S. Vose, A. Arguez, S. Applequist, and X. Yin, 2012: Computational Procedures for the 1981-2010 Normals: Precipitation, Snowfall, and Snow Depth. NCDC Report, 10 pp. PDF

  • For a detailed description of temperature Normals, see:

    Arguez, A., S. Applequist, R. S. Vose, I. Durre, M. F. Squires, and X. Yin, 2012: NOAA's 1981-2010 Climate Normals: Methodology of Temperature-related Normals. NCDC Report, 7 pp. PDF

  • For a detailed description of Hourly Normals, see:

    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. PDF

  • For more information about the "Constrained Harmonic Approach" used to calculate daily temperature Normals, see:

    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, in press. PDF

  • For information about the frost-freeze and growing degree day Normals, see:

    Arguez A., 2012: NOAA's 1981-2010 Climate Normals: Supplemental Normals. NCDC Report, 4 pp. PDF

  • The vast majority of the data used to calculate NOAA's 1981–2010 Climate Normals come from the Global Historical Climatology Network–Daily database. For more information on this database, see:

    Menne, M., I. Durre, B. G. Gleason, T. G. Houston, and R. S. Vose, 2012: An overview of the Global Historical Climatology Network-Daily database. Journal of Atmospheric and Oceanic Technology, 29, 897-910. PDF

    Durre, I., M. J. Menne, B. E. Gleason, T. G. Houston, and R. S. Vose, 2010: Comprehensive automated quality assurance of daily surface observations. Journal of Applied Meteorology and Climatology, 8, 1615-1633. PDF

  • The 1981–2010 temperature Normals are based on monthly temperature values that have undergone robust quality control and homogenization to address changes in observing practices. For more information on these techniques, see"

    Menne, M. J., and C. N. Williams, Jr., 2009: Homogenization of Temperature Series via Pairwise Comparisons. Journal of Climate, 22, 1700-1717. PDF

    Menne, M. J., Williams, Jr., C. N., and R. S. Vose, 2009: The United States Historical Climatology Network Monthly Temperature Data Version 2. Bulletin of the American Meteorological Society, 90, 993-1007. PDF