December 2021 Saint Cloud Weather Summary

Wet, Snowy December Completes Top 10 Warmest 2021

Annual 2021 St. Cloud Weather Summary

December Warmer Than Average Finishing 9th Warmest Year

December 2021 produced yet another milder than average month in St. Cloud. Despite a late month arctic surge, the St. Cloud Regional Airport average temperature was 19.9 degrees (avg. high: 29.6 deg, avg. low: 10.2 deg), 2.1 degrees above average. That total, combined with the rest of the year produced an annual 2021 average temperature of 45.4 degrees, the 9th warmest year of 130 in St. Cloud records. The recent spell of mild years has produced 11 years since 1998 in the top 25 warmest St. Cloud years. However, 2021 was one of the few with a top 10 warm summer (2021 and 1988 only summers within top 10 of past 85 years).

All months of the year, except February, ended up being warmer than average. This included 3 months ranking in their own top 10, including the 9th Warmest January, 7th Warmest March, and the 5th Warmest June. June featured a seven-day heat wave (days with consecutive 90-degree highs), the longest for so early in the season in St. Cloud. That heat wave produced two highs of at least 97 degrees in St. Cloud on the 4th and 5th. Those two days doubled the number of St. Cloud highs of at least 97 degrees since 2006 to 4.

December 2021 was on track to place within the 10 warmest Decembers, with a 25.6 degree average temperature through December 24. While there was a bit of a roller coaster tendency to temperatures, December had 9 days that were at least 10 degrees above average. There were two 50-degree highs, including the December 15 record daily high of 55 degrees. That was the latest in season 50-degree high since December 29, 1999 and the 6th latest in St. Cloud records (the latest was on December 31, 1904. The daily record warm low and warm average were also broken in St. Cloud and temperatures records were broken throughout the region, including a 64 degree high in Rochester.

However, enough cold air drained in from Canada at times to produce 11 lows of zero degrees or colder, one more than the December average.

Record Warmth Fueled Very Late Season Tornado and Derecho on December 15

The extreme warmth of December 15 was pumped into Minnesota ahead of a powerful storm that produced the entire range of weather from snow to severe weather. This system featured a derecho, a long-lived line of straight-line damaging wind storms which produced over 550 reports of straight line wind damage from Kansas to northern Wisconsin. Damage surveys done by the Twin Cities National Weather Service also showed that 20 tornadoes touched down in Minnesota, the first recorded December tornado outbreak (20) in Minnesota weather records, although records only go back to 1950. There were also three days with Minnesota tornadoes in October on the 9th, 10th, and 13th. This alone was the most tornado days after September since records began in 1950.

Before and even during the late season tornadoes, Minnesota had been having a mild to moderate severe weather year. And, even with the 4 days with tornadoes from October 1, 2021 didn't produce a late season record in number of tornadoes. That happened on October 26, 1996 when 14 tornadoes touched down.

The December 15 storm, which caused the tornadoes, the largest US straight line wind damage outbreak since 2004, as well as non-thunderstorm wind gusts of 75 MPH or higher, and significant snow, was voted the number 1 Minnesota weather event in the survey of meteorologists by the Minnesota State Climatology Office.

Third Wettest December in St. Cloud Records Was Often White

December 2021 was an extraordinarily wet and white month in Minnesota. At the St. Cloud Regional Airport, there were 2.01 inches of total precipitation (both rain and snow) during the month, 1.13 inches above averge. This was only the third December of 131 Decembers on record with at least two inches of precipitation. The wettest December was 2010 with 2.56 inches. There were 17 days with measurable precipitation in December, falling one day short of the 18 day record, set in December 1950. While precipitation took the form of rain, ice, and snow in December, there were 17.8 inches of snow recorded at St. Cloud State University, St. Cloud's official snow reporting site. That was 6.3 inches above average and missed by 0.2 inch breaking into top 10 snowiest Decembers. However, a strip of central Minnesota from New York Mills and Wadena through Brainerd and Hinckley got much more snow. These areas picked up 11-18 inches of snow on December 26 and 27 (St. Cloud got 4.4 inches), and another 3-6 inches of snow on December 29, so there were over 20 inches at several sites from the two storms. These storms replaced the deep snow pack from more regional storms earlier in the month, which made it easier for the late December arctic blast to produce typical cold readings (highs in the plus single digits, lows well below zero).

The 16 days in St. Cloud with measurable snowfall fell just 3 days short of the December record (19 days, set in 2013).

The frequent snow, combined with the alternating unusually mild days with at least average cold, also produced some rapid freezing of wet spots on area roads. One of these freeze ups produced a December 25 chain reaction crash along I-94 in Ashby.

December Snow Limited in Relieving Prolonged Dry Conditions of 2021

To some degree, the heavy December precipitation offset the prolonged, severe dry spell, which was at its most intense from the middle of spring until late in the summer. At the St. Cloud Airport, the worst precipitation shortfall was nearly 8 inches from May 1 through August 20. By late August (set US Drought Monitor Archive to August 24, 2021), all of northern and much of central Minnesota was in extreme drought, with exceptional drought from International Falls through the Red Lakes and into Fargo-Moorhead.Then, some late August and September rains eased the deficit somewhat. After that, December made the most progress, accounting for a 3-inch surplus from late August to the end of the year.

• St. Cloud May 1-August 20 rainfall (biggest deficit) 7.91 inches below average (6.03 inches actual, 13.94 inches average)
• St. Cloud August 21-December 31 precipitation: 3.17 inches above average (12.72 inches actual, 9.55 inches average)

While the eventual run-off from winter snow can help river and lake levels, it is not effective at easing ground water shortages, since the ground freezes before it accumulates. The alternating cold and warm spells allowed the ground to freeze early in the month.

The dry conditions during the summer produced a poor fire season over the western US mountains as well as in the boreal forests of northern Alberta, Saskatchewan, Manitoba, and Ontario. That combined with the relatively long rain-less periods allowed smoke from those wildfires to frequently make it into Minnesota, producing air quality typical at times of the worst days of Los Angeles smog.

The drought, smoke outbreaks in July and August, and June heat wave, as well as the two-week February period of intense cold, all ranked in the Mn State Climatology Top 5 Weather Events of 2021.

More to Come....