When we refer to temperatures or precipitation being above or below normal, what does “normal” really mean?
Climate normals are a statistically smoothed, quality-controlled, 30-year average of recent climate conditions.
“Normals put us in the context of where we are at and to tell us about our climate… for people who need that information to make decisions,” explained Dr. Michael Palecki, the project lead for the new normals.
NOAA scientists have compiled and reviewed more than 9,800 stations across the U.S. The result is an updated data set based on 1991-2020, to serve as the nation’s official climate normals for the next decade. By going through this process every ten years, it adds in new weather stations, helps to quality control the old, and allows us to keep pace with the most recent weather conditions across the nation.
Starting May 4th, these numbers can be used to provide a better baseline for many sectors of our economy…such as agriculture, electricity load planning, and construction scheduling.
Some of the notable changes from the previous time period include warmer temperatures for most seasons and most regions in the United States. However, that is not the case everywhere.
Palecki said that the north central U.S. in the winter and spring is quite a bit cooler, on the order of 1 to 2 degrees Fahrenheit.
For precipitation, the southeast and south central U.S. have seen notable increases for a majority of months. Unfortunately, much of the southwest has trended drier during the heart of the wet season from December through February, which is the time of year when the region needs to cash in on as much precipitation as possible.
Palecki explained, “It’s definitely an issue. You can have a high percentage change in the west in the summer when there is usually very little rain… but even a moderate change in precipitation during the winter when they get the bulk of the rain, that’s a very big issue for water supply.”
In addition to the conventional 30 year normals, this update will also develop the first set of 15-year normals, and other shorter-term interactive tools.
“A lot of our customers and users have requested to have shorter term data that matches more closely with current climate,” Palecki said.