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.
Rezaul Mahmood, director of the climate center based in the university’s School of Natural Resources, said the NCEI asked the climate center to develop the Custom Climatology Tool, which now allows users to examine average monthly and annual temperature measurements over customizable periods of time.
For anyone who works with climate data, the release of the new U.S. Climate Normals is a major event, Mahmood said. It tells the story of a changing climate. “Normal” 30-year temperature cycles have grown warmer over time. “Normal” annual precipitation has increased, too. As an NOAA news release about the U.S. Climate Normals states, global warming is affecting the upward trajectory of the new normals. The Custom Climatology Tool allows people to look at what normal used to be with available weather station data from as far back as 1961.
“NCEI was getting requests, and we would get them, too, from stakeholders and users who would say: ‘The 30-year normal is fine, but I want to do a 10-year average or a seven-year average. I should be able to pick any time and go from there.’ So that motivated NCEI to talk to us and ask if we could build that,” Mahmood said.
Mahmood said the tool allows users to dive into decades’ worth of data in a manageable way. Someone interested in how temperatures in Lincoln differ this May from the Mays of their childhood, for instance, can search weather station data collected at the Lincoln Airport and set parameters that develop averages based on five years, a decade, 30 years or any number they prefer. The U.S. Climate Normals inform all kinds of operational decisions across a number of industries, Mahmood said, from when to plant crops in Nebraska to how much freight gets loaded on a Mississippi River barge. Users of the Custom Climatology Tool can gain additional context, he said, and satisfy human curiosity about their surroundings in the process.
“We always get curious about the weather,” he said. “‘OK, today is hot, but how hot is it? I’m thinking it is very hot, but maybe it’s not very hot.’ It’s linked to our life.”
The Custom Climatology Tool, which was developed in collaboration with NCEI staff, is available on the High Plains Regional Climate Center website here. Climate center programmers Warren Pettee and Willaim Sorensen developed the tool with help from regional climatologist Natalie Umphlett and applied climatologist Crystal Stiles.