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Record Cool Spell for Mid-July: July 18, 2014 Commentary

In this edition of WeatherTalk

  • Record cool spell for mid-July 
  • New Seasonal Climate Outlook
  • Anniversary week for Minnesota's top rain storm
  • Weekly Weather potpourri
  • MPR listener question
  • Almanac for July 18th
  • Past weather 
  • Outlook

Record cool spell for mid-July

On Monday, July 14 a cold air mass from Canada invaded the state and brought record-setting cold high temperatures to scores of communities. Winds were strong from the north and remained so throughout much of the day and the night, so no overnight minimum temperature records were set. But the cooler, drier air from the north held down daytime temperatures into the 50s and 60s F across the state. Some observers reporting new record cold highs for the date included: 57 degrees F at Silver Bay, Isabella, Bigfork, and Embarrass; 59 degrees F at Crane Lake, Cloquet, and Ely; 60 degrees F at International Falls, Brimson, Leech Lake and Mora (tied with 1960); 61 degrees F at Moose Lake, Grand Rapids, and Bemidji (tied with 1961); 62 degrees F at Park Rapids; 63 degrees F at Moorhead, Alexandria, and Waskish (tied with 1994); 64 degrees F at Brainerd, Wheaton, Dodge Center, and Detroit Lakes; 65 degrees F at MSP, St Cloud, Baudette, Preston, and Waseca. High wind gusts over 30 mph were prevalent with the cold air advection at places like St Cloud, Warroad, Alexandria, Grand Rapids, and even the Twin Cities.

The cold air took residence for about 48 hours and brought new record cold mean daily temperatures (average of the maximum and minimum values for the day) to many communities on Tuesday, July 15th. Some of these records include: 55 F at Pipestone; 57 F at Windom; 58 F at Waseca and Grand Meadow; 59 F at Zumbrota, Austin, and Winnebago; and 60 F at Rochester.

Finally, clear skies, high pressure, and calm winds brought some record minimum temperature values on Wednesday morning to northern and western parts of Minnesota. Some of the new records included; 35 F at Brimson; 38 F at Hibbing (tied 2007); 39 F at International Falls, Silver Bay, Crane Lake, Eveleth, and Orr; 45 F at Wheaton; and 46 F at Marshall and Worthington. The cold air finally cleared out on Thursday, and in contrast much of the balance of the month looks to be warmer than normal with above normal rainfall as well. That's Minnesota!

New Seasonal Climate Outlook

The NOAA Climate Prediction Center released new seasonal climate outlooks this week for the period August through October. The outlook favors cooler than normal temperatures for the western Great Lakes Region, including Minnesota. This is consistent with the pattern so far observed in July which shows most observers reporting mean monthly temperatures that range from 3 to 5 degrees F colder than normal.

The precipitation outlook is neutral, with equal chances for above or below normal values across the region during the August to October time frame. In any event, rainfall for the balance of the 2014 growing season is likely to be more variable across the Minnesota landscape.

Anniversary Week for Minnesota's Top Rain Storm

Today (July 18) is the anniversary of perhaps the most prolonged intense rainfall ever recorded in the state. This thunderstorm complex occurred in 1867 over western and central Minnesota, but was especially heavy in parts of Douglas, Pope and Stearns Counties, affecting the pioneer communities of Osakis, Westport, and Sauk Centre. Beginning late on Wednesday, July 17th, lasting all day July 18th, and into the early morning of Friday July 19th, heavy thunderstorms drenched the landscape with up to 30 inches of rainfall. Unfortunately measurements of the storm were not made by official rain gages in those days, but several people did record measurements via buckets and barrels which filled up. George B. Wright, a pioneer land surveyor in the area, documented the event and reported on it in some detail to the Minnesota Academy of Natural Sciences years later (1876). In his account, the Pomme de Terre, Chippewa, and Sauk Rivers, normally creeks at that time of year, became lakes several miles wide. The storm generated runoff caused the Mississippi to rise several feet (up to 12 ft in places), washing out bridges and logging booms right through the Twin Cities area. The total number of logs washed away was estimated to exceed 25 million. The mosquito population was reported as the worst ever for the balance of that 1867 summer. Even through the modern era this storm rainfall total has not even been approached. The greatest in the modern era was 17.21 inches near La Crescent, MN during the famous August 19, 2007 flash flood there.

Weekly Weather potpourri

NOAA released its State of the Climate in 2013 report this week. It highlights continued warm temperature trends and rises in sea level. It also highlights changes in Arctic sea ice, and regional climate trends. The report is 232 pages, but you can read the highlights.

With a return to warm, humid weather across the state next week, we may seen some Heat Advisories issued by the National Weather Service. In this context it might be wise to review some tips for maintaining good health during these hot spells. NOAA Public Affairs has issued four tips on preparing for heat spells. 

In addition, the EPA offers a guide book on coping with excessive heat and it too is available online as a PDF file. 

Late last month the city of Denver, CO released its first Climate Adaptation Plan. It is a comprehensive look at preparing for three features of the climate which are expected to change there: Increased temperature and urban heat island effects; Increased extreme weather events; Reduced snowpack and earlier snowmelt season. You can read more about this plan from the press release.

NOAA National Climatic Data Center recently released the statewide ranks for June temperature and precipitation in 2014. The Great Lakes Region had the wettest June in history, while the far west, notably CA and AZ had one of the warmest June months in history. You can view these rank maps at the NCDC web site.

Additional news from the western states is that Lake Mead is now at a historical low due to persistent drought in the west. Formed by the Hoover Dam, Lake Mead is the largest reservoir in the western states NV and AZ.

The Joint Typhoon Warning Center was issuing statements this week on Super Typhoon Rammasun which was headed for Vietnam and South China. Wind gusts were over 160 mph, creating sea wave heights of 35-40 feet. It will bring heavy rains to coastal areas throughout the coming weekend. Further north Tropical Storm Matmo was heading towards the coast of China between the Philippines and Japan. It was expected to strengthen over the weekend.

A NASA press release this week celebrates the 10th anniversary of the Aura Satellite system. Its package of instruments measures many of the greenhouse gases in the atmosphere and tracks their seasonal distribution. These data have been useful in tweaking climate models. Read more.

MPR listener question 

"It seems like our temperatures in Minnesota are always well above or well below normal. How do the standard deviations of temperature vary by season and are the standard deviations of daily temperatures larger here than in other states?"

Answer: Indeed the standard deviations in daily temperature do vary considerably by season. They are at their lowest values now (July). For example in July for the Twin Cities the standard deviations of daily maximum and minimum temperature are about plus or minus 6-7 degrees F. So the high temperature of 65 degrees F on Monday, July 14th in the Twin Cities was about 3 standard deviations from the mean maximum temperature value for the day (84 F). In contrast the standard deviations for daily maximum and minimum temperatures are plus or minus 13-15 degrees F during January when temperature variations are more amplified by cloud cover, air mass and presence or absence of snow cover.

Comparing to other geography, we can see that at Huntsville, Alabama this time of year the standard deviations of daily maximum and minimum temperature are just 3-4 degrees F, while in January they jump up to 10-11 degrees F, less than the variation we experience in Minnesota.

Twin Cities Almanac for July 18th

The average MSP high temperature for this date is 84 degrees F (plus or minus 7 degrees F standard deviation), while the average low is 64 degrees F (plus or minus 6 degrees F standard deviation).

MSP Local Records for July 18th

MSP weather records for this date include: highest daily maximum temperature of 101 degrees F in 1940; lowest daily maximum temperature of 60 degrees F in 2000; lowest daily minimum temperature is 49 degrees F in 1873; highest daily minimum temperature of 80 F in 2011; record precipitation of 2.94 inches in 1895; and there has been no snow on this date.

Average dew point for July 18th is 62 degrees F, with a maximum of 81 degrees F in 2011 and a minimum of 44 degrees F in 2009.

All-time state records for July 18th

The state record high temperature for this date is 109 degrees F at Beardsley (Big Stone County) and Morris (Stevens County) in 1940. The state record low temperature for this date is 30 degrees F at Kelliher (Beltrami County) in 2003. State record precipitation for this date is 7.50 inches at Fort Ripley (Crow Wing County) in 1867; and no measurable snowfall has occurred on this date.

Past Weather Features

One of the coldest mid-July spells of weather occurred over July 18-19, 1912. Many observers reported overnight lows dropping into the 30s F, and some like Cloquet, Littlefork, and Roseau reported a mid-summer frost that damaged plants.

The hottest July 18th in history was in 1940 when over 25 communities reported daytime highs of 100 degrees F or greater. The coolest spot in the state that day was the Grand Marais Harbor with a high of just 59 degrees F. The July 1940 Heat Wave lasted until the 26th when a cold front brought rain and temperatures dropped into the 60s F.

Very strong thunderstorms moved across central and northern counties of Minnesota over July 17-18, 1952. Many observers reported 2-3 inches of rainfall, and a number of country roads and highways were flooded. Some record setting rainfalls included 6.10 inches at Gull Lake, 7.75 inches at Moose Lake, and 10.17 inches at Aitkin.

Between 6:00pm and 7:00pm on July 18, 1970 two tornadoes formed over central Minnesota. The first with winds over 158 mph tracked 4 miles across Douglas County near Lake Miltona, and it damaged several businesses, 28 homes, and 6 farms. The second tornado was on the ground in Anoka County for just 1 mile near Soderville. It damaged just a few homes.


Near normal temperatures on Saturday with a chance for showers and thunderstorms. Warmer on Sunday and Monday with a possibility of a heat advisory for some areas because of higher dewpoints. Chance for showers and thunderstorms on Tuesday and Wednesday of next week, with temperatures dropping back to near normal levels.

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