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Preliminary Climate Summary for May

Preliminary Climate Summary for May:

Though temperatures fluctuated considerably during May, most observers report a mean monthly temperature that is 1 to 2 degrees F cooler than normal. Extreme values of temperature ranged from 87F at several western and southern climate stations on multiple dates to just 23F at Isabella on the 20th. Minnesota did not report the coldest temperature in the nation on any date in May.  Multiple frosts occurred during the month, and some spotty damage was noted on soybean and sugar beet fields.

The most notable feature of the month was surplus rainfall.  Most climate stations reported above normal rainfall amounts, and in some cases twice normal rainfall.  The wettest part of the state was across the central counties where 4 to 6 inch amounts were common.  Many places reported measurable rainfall on half the days of the month.  Over 40 communities reported new daily record rainfall amounts for selected dates during the month.  Some of these stations included: 2.40 inches at Minnesota on the 10th; 2.25 inches at Madison on the 11th; 2.00 inches at Montevideo on the 11th; 2.22 inches at Wheaton on the 11th; 2.75 inches at Collegeville on the 17th; 3.22 inches at Morris on the 17th; 3.65 inches at Lake Wilson on the 17th; and 2.10 inches at Hallock on the 18th.  Overall some of the highest total rainfall values for the month exceeded 7 inches at places that included Morris, Montevideo, Cass Lake, and Ottertail, Some places in northern Minnesota reported small amounts of snowfall for the month including Tofte, Two Harbors, Orr, and Isabella

These so-called "rescue rains", a term used by many Minnesota farmers, helped transform the state drought situation significantly during May.  When the month started over 94 percent of the state landscape was in moderate to severe drought, and as of the end of the month, less than 25 percent of the state is still in moderate drought, quite a remarkable turn-around.  This was the 5th consecutive year that May has delivered above normal rainfall to the state, and May of 2015 will probably rank among the 15 wettest in state history.

In contrast to the month of April, wind speeds were generally less than normal during the month of May in most places around the state.  There were a few severe thunderstorms with strong winds, and on May 16th tornadoes were reported in Lac Qui Parle, Chippewa, Pope, Swift, Meeker, Wright, and Stearns Counties.  Fortunately no cities were hit by these storms, though there was some damage to barns near Darwin in Wright County and some tree and roof damage in Swift and Chippewa Counties. They were the first tornado reports in Minnesota for 2015.

Comparing Drought-Busting Rainfalls in MN, OK, and TX:

Earlier this week I commented in Facebook about comparative rainfall this month, that has busted drought in Minnesota, and set many records in the states of Oklahoma and Texas:

May 1-29 2015 rainfall in Minnesota (climate stations with roughly twice normal)

7.03" at Moorhead
7.02" at Cass Lake
7.19" at Park Rapids
7.01" at Montevideo
8.41" at Ottertail
7.31" at Morris
6.05" at Collegeville
6.50" at Brainerd
6.68" at Lake Wilson

May 1-29, 2015 rainfall in Oklahoma (climate stations with roughly 4 times normal)

McAlester 22.25"
Blanchard 23.91"
Norman 22.68"
Lehigh 24.10"
Anadarko 20.99"

May 1-29, 2015 rainfall in Texas (climate states with 3-4 times normal)

Muenster 20.13"
Gainesville 21.43"
Kendalia 20.83"
Houston (Sugarland) 18.03"

All of the reports from Oklahoma and Texas are either new record amounts for the month of May, or new record amounts for any single month of the year.  Widespread, destructive flash flooding has occurred in both Texas and Oklahoma.

Weekly Weather Potpourri:

I will be at Valley Bookstore in Stillwater, MN at 2 pm this Saturday, May 30th to talk about the 2nd Edition of the Minnesota Weather Almanac.  I would be happy to sign copies of the book and answer any weather questions.  Please drop by if you are in the area.

Jim Angel, State Climatologist for Illinois, wrote an interesting article this week for the Sustainable Corn Blog.  It is about the potential impact of the current El Nino episode on the Corn Belt states.  It is worth a read.

The NOAA-Climate Prediction Center issued their outlook for the 2015 Atlantic Hurricane Season this week.  They call for a 70 percent chance that the season will bring 6-11 named storms and 3-6 hurricane level storms (winds 74 mph or greater).  They primary basis in forecasting less than normal activity for the hurricane season in the Atlantic Ocean Basin is the presence of El Nino.  

NOAA announced a new climate monitoring blog this week that will provide updates on trends and record-setting values in the nation's climate monitoring networks, as well as the global networks.  Hearing from the "official scorekeepers" of climate events should provide for an interesting blog. 

The first named tropical storm of the Eastern Pacific Hurricane Season formed this week.  Tropical Storm Andres was spinning at seas about 700 miles south of the tip of Baja California.  It was expected to strengthen to hurricane status (winds greater than 74 mph) over the weekend, but remain out to sea.

The Hadley Centre in the United Kingdom celebrated its 25th anniversary this week.  Scientists there have made significant contributions to global climate monitoring networks, development of climate models, and assessment of future climate impacts. 

A lethal Heat Wave has plagued the central states of India during the 2nd half of May, bringing high daytime temperatures of 114 to 118 degrees F to many areas, with nighttime lows remaining in the upper 80s to low 90s F.  Over 1400 deaths have been blamed on the Heat Wave and it is expected to last until near the end of May, before the monsoon season brings increased cloudiness and chances for rain.  CNN did a report on this earlier in the week. 

MPR Listener Question:

 Hearing reports of snowfall in northern Minnesota this month made me wonder how often does May bring snowfall to northern Minnesota communities?


Fairly frequently.  The historical frequency for measurable May snowfall at places like International Falls and Duluth is about once very other year.  Other northern locations like Big Falls and Tower have historical frequencies of May snowfall that are close to once every three years.

Twin Cities Almanac for May 29th:

The average MSP high temperature for this date is 74 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 54 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for May 29th:

MSP weather records for this date include: highest daily maximum temperature of 94 degrees F in 2006; lowest daily maximum temperature of 53 degrees F in 1947: lowest daily minimum temperature is 33 degrees F in 1965; highest daily minimum temperature of 74° F in 2006; record precipitation of 2.49 inches 1942; and no snowfall has been recorded on this date.

Average dew point for May 29th is 50 degrees F, with a maximum of 72 degrees F in 1953 and a minimum of 25 degrees F in 1947.

All-time state records for May 29th:

The state record high temperature for this date is 101 degrees F at Chaska (Carver County) in 1934. The state record low temperature for this date is 20 degrees F at Bigfork (Itasca County) in 1965.  State record precipitation for this date is 7.50 inches at Thief River Falls (Pennington County) in 1949; and the state record snowfall for this date is 2.6 inches at Spring Grove (Houston County) in 1947.  

Past Weather Features:

The historic Heat Wave of May 27 to June 2, 1934 brought some of the highest temperatures ever measured in May.  May 29th was the hottest in history that year with over 50 climate stations reporting daytime highs of 90 degrees F or higher, and a dozen communities reaching or surpassing 100 degrees F.

Strong thunderstorms brought record-setting rainfall and flash flooding to many parts of the state over May 29-30, 1942.  Red Wind and Zumbrota received over 4 inches of rain, but most of the real damaging rainfalls occurred around the Twin Cities area.  Minneapolis downtown reported 7.07 inches, downtown St Paul received 5.89 inches, and Maple Plain reported 6.40 inches.  Many roads were underwater for a day or two.

A strong thunderstorm on May 29, 1949 dropped 4.50 inches of rain on Mahnomen and 7.50 inches of rain on Thief River Falls in a period of just 6 hours.  Many farm fields were flooded, but eventually recovered.

May 29, 1947 brought widespread damaging frosts to many parts of the state.  Morning low temperatures in the 20s F and low 30s F were common throughout the state causing crop damage and damage to tender garden plants as well.  Frosts occurred as far south as Austin and Grand Meadow, while Thief River Falls in northwestern Minnesota went down to just 21 degrees F.  For a brief time on May 29th a freak snow storm occurred depositing a trace of snow in many places and some measurable amounts in a few spots including Spring Grove, Albert Lea, Harmony, Tower, Caribou, Baudette, Worthington, and Grand Meadow.

Thunderstorms and heavy rains over May 28-30, 1953 caused the Red River to reach flood stage in northwestern Minnesota.  Many observers in the northwestern counties reported 2 to 5 inches of rainfall over that time period.  Roads and culverts were washed out in parts of Wilkin, Clay, and Ottertail Counties, and a 500 foot section of railroad tracks washed out in northern Wilkin County, taking weeks to repair.

May 29, 1965 brought another widespread frost, damaging many corn fields around the state.  In the north temperatures fell into the 20s F in many places and widespread frosts were noted even in the suburbs of the Twin Cities.  In southeastern Minnesota Caledonia reported a low of 27 degrees F, while Zumbrota reported just 28 degrees F.


Mostly sunny, with cooler than normal temperatures over the weekend, and a chance for frost in the extreme northeast.  Returning to near normal temperatures by Tuesday of next week, but with a chance for showers and thunderstorms over Tuesday through Thursday.  A return of higher dew points and daytime temperatures in the 80s F as well.

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