1981-2010 Climate Normals

What are normals?

In a general sense, a "normal" is the expected value (e.g., temperature, precipitation amount, etc.) for a particular location during a particular time of year. Normals help describe a location's climate by quantifying certain elements, such as precipitation seasonality (i.e., when during the year precipitation tends to fall.) For monthly and annual values, normals are typically the average values during the 30-year period. Distinctly different from averages, daily normals (1981-2010) were computed using a harmonic fit, a statistical method which dampens the effects of outliers, creating a smooth transition between adjacent days. (A cubic spline based on monthly means was used to compute 1971-2000 normals.)

Why does NOAA produce 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 National Climatic Data Center (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, the predecessor to the National Weather Service, as a civilian agency.

For what purposes are normals used?

Meteorologists and climatologists regularly use normals for placing recent climate conditions into a historical context. NOAA's normals are commonly seen on local weather news segments for comparisons with the day's weather conditions. In addition to weather and climate comparisons, 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.

Our year-to-date precipitation departure from normal suddenly changed on August 1. Is this a problem?

Departures from normal help gauge extreme events, such as the current drought. The utility of this concept is not lost when new normals are introduced, but when new normals are noticeably different from the previous iteration, departures from normal may appear more or less impressive.

Are there any significant differences between the 1971-2000 normals and the values for 1981-2010?

For our region, the 1981-2010 normals are generally warmer and wetter than the 1971-2000 normals. These changes are not uniform across the Texas and Oklahoma Panhandles for a number of reasons, including the impacts of urbanization and inconsistencies in siting and instrumentation. Data from 1981-2000 are included in both sets of normals, so the changes are based on the differences between 1971-1980 and 2001-2010. In a nutshell, the most recent decade was warmer and wetter than the 1970s. View a comparison of differences in the 1971-2000 normals and the 1981-2010 normals for Amarillo, Borger, Dalhart, and Guymon.

Is our climate becoming warmer and wetter?

The climate of a particular location changes over time, but climate normals were not designed to be metrics of climate change. They may capture recent trends, giving a better perspective of the current state of the climate, but changes between sets of normals do not necessarily confirm a trend. Because of the rigidity of the 30-year time period, a trend on shorter or longer time scales may not be represented. When coupled with other issues, including the aforementioned urbanization, siting, and instrumentation, the changes from one set of normals to the next are not necessarily reflective of real changes in the underlying climate signal. Normals aim to provide expected values, but they cannot and do not provide a prediction of the future state of the climate.

Are snowfall normals available now?

Not for every location. Snowfall normals have been calculated for some locations, but there are some concerns about the completeness of the data set used to calculate them. The National Weather Service and the National Climatic Data Center are working to resolve this issue.

For more climate normals FAQs, please visit the National Climatic Database Center.