Heat in Yellowstone National Park, Wyoming

Most of the second half of March featured record breaking warmth in Yellowstone Park, including at Lake Yellowstone. Daily average temperatures for the period March 17 to March 30 averaged more than 15 degrees above normal. Eight near daily record high temperatures were set. The all time monthly high temperature of 57 degrees was broken on four consecutive days from March 18 to March 21. And, there was the first occurrence of 60 degrees in March in station history on March 19, more than a month earlier than previous earliest occurrence on April 22, 2016. Records at Lake Yellowstone date back to 1998.

A very strong ridge of high pressure set up across much of the western United States and brought an long period of record breaking warmth. The most impressive stretch was from March 18 through March 21. In total, 71 new daily record high temperatures were set out of a possible 126 high temperatures at RIW CLI sites (longer term climate sites), greater than half of the daily highs. Every location was at least 10 degrees above normal through the period. Every location had their all time warmest period for these two weeks, with three locations; the Riverton Airport, the Sweetwater County airport near Rock Springs, and the Lander airport; more than 8 degrees above the previous warmest period. All locations set their all time high temperature March multiple times in this stretch. Six locations had their earliest 80 degree high temperature, with four stations having their first 80 degree or greater March high temperatures in station history.