Welcome to the new climate normals

Meteorologists were using records from 1971-2000 to calculate “normal.” Beginning August 1, 2011, they are using records from 1981-2010.

Today is August 1, 2011, so our climate normals have changed.

We meteorologists have been using relatively old records to determine our average high/low temperatures, precipitation and so on. These records were based from the year 1971 to the year 2000. Beginning today, normals will be from 1981-2010.

What’s going on here? The term “normal” – according to NOAA’s National Climate Data Center (NCDC) – is technically “the latest three-decade averages of climatological variables, including temperature and precipitation.” So normal, for NCDC, is really an average of the past 30 years – the previous three completed decades.

So now once every decade NCDC re-calculates the average and calls it our “normal.” Beginning August 1, we are using 1981-2010.

Climate averages NOAA

Image Credit: NOAA

The NCDC is now using this new 30-year average for various reasons:

  • Stations may have relocated
  • Instrumentation at various locations have been upgraded or changed
  • Changes in methodology
  • It will include a suite of metrics, including daily probabilities of precipitation with month-to-date and year-to-date precipitation normals.

You can learn more about the climate normals by visiting the NCDC.

You can also locate the normals from each state through 1981-2010 from the Department of Atmospheric Sciences at the University of Washington.

Image Credit: Missouri Skies

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