When a meteorologist says that a chilly day in May was 12 degrees lower than normal, the normal being referenced is typically from the official 30-year U.S. Climate Normals. Updated every decade, the Normals are based on 30-year averages of climate observations recorded at thousands of weather stations across the country.
On May 4, the 1991-2020 U.S. Climate Normals are being released by the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information (NCEI). In conjunction, the University of Nebraska–Lincoln’s High Plains Regional Climate Center is publishing a new tool that allows users to examine what normal looks like relative to longer or shorter timeframes than the most recent 30 years.