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Wet, Normally Cool May Temperatures Leave Few Happy Campers

May and Spring 2011 Saint Cloud Weather Summaries

After having one of the longest periods of continuous snow cover in St. Cloud records, area residents were certainly ready for a fast spring. Instead, the wet and seasonably cool weather continued through May. Measurable rain fell on 15 of the 31 May days in 2011, the most rainy May days since 1993. There were several Mays with more rainy days in the 1970's, the rainiest period in relatively recent memory. However, all of these Mays pale before the miserable May 1938. In that month, it rained on 24 of the 31 days with a total rainfall of 6.80 inches, the 4th rainiest May in St. Cloud records.

The frequent May rain continued the trend of this year so far. St. Cloud has now had measurable precipitation on 58 days from January 1 through May 31. That's the fourth highest total in the 116 years of St. Cloud precipitation records and the most since the 67 precipitation days set in 1979. There have now been 29 days with at least 0.10 inch of rain since the start of the year. The only year that had more events in the first five months of the year was 1938 with 32 days.

Unless March and April, St. Cloud more frequent substantial rainfall. The May total rainfall at the St. Cloud Municipal Airport was 5.51 inches, more than two and a half inches higher than the average May rainfall of 2.96 inches. That still ended up being about a third of an inch short of the ten wettest Mays in St. Cloud records. For the spring (March 1-May 31), St. Cloud had 9.68 inches, about 3 inches more than normal. For the calendar year so far,

The frequent rain this spring has mainly come as cool air masses held fast in southern Canada into the Northern Tier of states, while most states near the Gulf Coast remained much warmer than normal. So, when any storm moved across the US to the east of the Rockies, the warm and cool air were packed tightly together. That gets the upper-level winds blowing strongly, keeping the storms strong and raising the possibility of severe weather. As St. Cloud got into warmer weather at times later in the month, the big temperature contrast between warm and cold continued, but the storm track moved closer to us. The biggest effect was the heavy rain, including 2.40 inches of rain on May 20-22 (more rain than during either March or April) and 1.31 inch on May 30-31.

Rainy Weather Spawn Severe Storms In Minneapolis and Elsewhere

These rains also produced some severe weather, including a tornado outbreak on May 22 that included the north Minneapolis tornado that killed one person and produced EF-1 damage.

Actually, during our warm early May period, severe weather nationally had a lull from the record number of tornadoes (875 estimated) seen in April, but that radically changed for the second two-thirds of May. May ended up with over 340 reports of tornadoes, including the Joplin storm on May 22. That tornado appears to have produced the largest reliable single tornado death toll (132 people) and the 8th largest of all time. 18 people were killed in 4 states on May 24.

The national death toll stands at 512 people, the second highest total since extensive storm damage surveys began in the 1950's behind the 519 killed in 1953, and the 7th most on record, according to historical studies by tornado researcher Tom Grazulis. The day of the Birmingham-Tuscaloosa tornadoes (April 27) still stands as the large daily tornado death toll (314) since reliable records began (and the 4th on record) and the Joplin storm (132) stands as the largest reliable single tornado death toll and the 8th largest of all time.

The problem is that these storms, up to last weekend, keep hitting significant-sized cities like Tuscaloosa, Birmingham, and Joplin. We are also beginning to get hints that these storms are hitting areas where there aren't old-fashioned storm shelters (think of the storm cellars in Places in the Heart or The Wizard of Oz) or basements. When these large wedge tornadoes hit homes, being in an interior room below ground is the key to survival. And the myth that tornadoes can't hit large cities is still out there.

Despite the Rain, Near Normal Temperatures Reigned

All of the rain helped to suppress average temperatures as well, but only to around the average value. The meteorological spring (March 1-May 31) average temperature, according to the statistics from the Saint Cloud Municipal Airport, was 41.2°F, 1.9°F cooler than normal. However, the cooler than normal readings were mainly due to the chilly March (4.1°F cooler than normal). Both April and May had an average temperature within a degree of normal. That's a marked contrast, however, from last year, which had an average temperature of 48.6°F, 7.4°F warmer than this spring and the 4th mildest spring of all time.

May 2011 seemed to be quite chilly, especially given the longing for warm weather. However, May 2011 in St. Cloud ended up being close to normal. The average St. Cloud May temperature was 55.6°F, 0.9°F cooler than normal. It was also a degree and a half cooler than last May, but warmer than both the Mays of 2008 and 2009.

There were three chilly periods during May. The coldest of these were the first 4 days of May. This marked the second half of a week of a cool blast that moved in during late April, but the worst day of this outbreak was May 1, when the high temperature didn't even make it to 40 degrees. The May 1 record for coldest high temperature was broken with only a 39°F high and a record for the coldest average temperature was tied. There were also some snow flurries. There were also four sub-freezing lows in early May, including a 26°F low on May 3. Then, we had a week of warmer weather, including St. Cloud's first 80-degree high of the warm season on May 10. However, that was followed by another mid-month cool period, during which the high didn't make it to 70 degrees for 6 straight days. Then, there was a late month cool period in which the high never got warmer than 72.

The early May coolness was especially unnerving since it came at the end of a 21-day streak (since April 14) without a temperature above normal. For the entire spring, 50 of the 92 days had cooler than normal temperatures. In contrast, there were only 16 days last spring that were cooler than normal.

Consequences of the Wet, Cloudy Weather

The wet and cool conditions has led to an explosion of pollen. Once temperatures finally broke the long below normal streak this month, trees budded and grass grew on a rapid rate. This has led to a tough spring for allergy sufferers.

Agriculture has suffered due to the wet conditions. The May 31 edition of the weekly Minnesota Crop Weather Report shows that there is surplus moisture in 45% of the state's topsoil. Planting is also well behind the 5-year average and last year, but note that most of the recent springs have been warm and dry. That allowed field work to proceed at a rapid rate, but the prolonged dry periods led to problems with grass fires and dry topsoil during the past few springs.

Start of June Looks Warmer

To start the meteorological summer (June 1-August 31), the new weather pattern shows high pressure in control of the southeast and south central states. That has pushed the storm track near or into southern Canada already. This should allow St. Cloud to get June off to a warm start with alternating periods of normal and above normal temperature.

Cool Early May Weather Ends Trend of Early Spring Thresholds

The coolish early May weather delayed the first 70-degree high of the year to May 4, which is 17 days later than normal. However, it looks like the last frost of the season took place about two weeks early than usual. There has never been a frost in St. Cloud later than June 1, so it should now be safe for all plants.

St. Cloud Threshold 2010 Date Average (1896-2011) Rank
First 50-degree high March 14 March 26 52nd latest
First 60-degree high March 14 April 14 43rd latest
First 70-degree high May 4 April 17 7th latest
First 80-degree high May 10 May 4 44th latest
Last 32-degree low May 4 May 18  
Last 28-degree low May 3 April 30  

Tied for Fewest Frosts In A Cold Season

The last frost on May 4 was the 168th day with a frost during the cold season of 2010-11, which is two short of the normal total. However, that was a big change from the 152 such days set last cold season, which tied for the fewest number of days with frost.

 

 

    

May 2011 Statistics

 

 

 



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Send comments to: raweisman@stcloudstate.edu
Last updated: June 1, 2011
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