The average temperatures in the contiguous U.S. over the last three decades, or “climate normals,” reached a record high, according to a Washington Post analysis of data released by the National Oceanic and Atmospheric Administration.
From 1991 to 2020, the 30-year average was 53.28 degrees Fahrenheit for the 48 contiguous U.S. states, a record high. The area has warmed 1.7 degrees, roughly equivalent to the world as a whole, since 1901-1930, the first three-decade period for which climate normals were recorded.
NOAA data indicated climate normals increased 0.46 degrees from the 30-year period between 1981 and 2010 to the period between 1991 and 2020. This is the second-highest increase on record for the country, after the 0.5-degree increase between 1971 and 2000, and 1981 and 2010, according to the Post.
Normals are used for a variety of applications, including utility rate-setting, agricultural planning and in some cases simply for forecasters to compare specific dates to their historical averages.
“What we’re trying to do with climate normals is to put today’s weather in a proper context so we understand whether we’re above normal or below normal and also we’re trying to understand today’s climate so people know what to expect,” Michael Palecki, who manages NOAA updates to the data, told the Post.
During the same three-decade period, precipitation also increased, according to the data, going from a national average of 30.97 inches from 1981-2010 to 31.31 inches from 1991-2020. Much of that increase was specifically in the eastern U.S., while the overall trend was dryer in the southwestern U.S.
“‘It varies’ is the main message of the maps showing how the normal annual precipitation across the country has changed. Precipitation — regardless of human-caused climate change — varies a lot from place to place across the United States,” Rebecca Lindsay wrote at Climate.gov in April. “Few places exhibit a precipitation trend that is either steadily wetter or steadily drier than the 20th-century average. Instead, drier areas and wetter areas shift back and forth without an obvious pattern.”
