August Climate Summary

August Climate Summary:

Average temperature for the month was generally from 1°F to 3°F warmer than normal at most climate stations, except for northeastern Minnesota, where the monthly average was near normal or slightly cooler than normal by 1 or 2 degrees. Many areas reported multiple days with 90°F temperatures, and at least 16 climate stations reported a day with 100°F or greater. Extreme values of temperature across the state ranged from 104°F at Winona airport on August 23 to just 36°F at Brimson (St Louis County) on the morning of August 27.

During the month across the Minnesota official climate station network at least 69 daily maximum temperature records were set or tied, mostly over the Heat Wave of August 21-24. In addition, at least 49 record warm daily minimum temperature records were set or tied., including a very warm minimum temperature of 80°F at Lake Wilson (Murray County) on August 23. The stress of record-setting warm temperatures, especially during the Heat Wave was compounded by record-setting dew points as well. Many climate stations reported dew points between 75°F and 80°F. MSP set new daily dew point records on consecutive days with readings of 79°F on August 22 and 78°F on August 23. A number of Minnesota communities also reported record daily Heat Index Values ranging from 110°F to 120°F. This Heat Wave is summarized in more detail at the Minnesota State Climatology Office web site.

As has been the case since May, the rainfall pattern for August was very spotty across the state. Except for portions of west-central Minnesota and a few areas around the Twin Cities, most of the state saw less than normal rainfall, especially in the northwestern and southeastern counties. Thunderstorms brought heavy rains at times and produced some new daily record amounts at some climate stations. At least 20 climate stations reported a record-setting daily rainfall, including Browns Valley with 2.95 inches and Milan with 2.80 inches on August 14th. Some areas of western Minnesota reported over 5 inches of total rainfall for the month, as did a few spots like Roseville, Columbia Heights, and Buffalo around the Twin Cities. In contrast, many parts of northern and southeastern Minnesota reported less than 1.5 inches of rain for the month. A few climate stations were historically dry in August. For example, Baudette (Lake of the Woods County) reported only 0.69 inches of rainfall, their driest August in history; while Caledonia (Houston County) reported just 0.76 inches of rainfall, their 4th driest August in history.

In looking at the impact of August weather on Minnesota’s drought situation, over the course of the month the area covered by Moderate Drought or worse changed relatively little, staying between 75 percent and 79 percent; the area covered by Severe Drought or worse increased by 5 percent, while the area covered by Extreme Drought increased by7 percent (3 pct to 10 pct). Extreme Drought expanded most notably in southeastern counties, where many climate observers reported less than half the normal monthly rainfall.

From the standpoint of severe weather, August 11th brought large hail to many parts of the state. There were more than 35 reports of large hail (1 inch diameter or bigger) on that date, along with 19 reports of damaging winds. There was also a brief tornado touchdown in Nobles County on August 13th, but no reported damages.

Weekly Weather Potpourri:

The Weather Underground web site provides a good statistical summary of the impact of Hurricane Idalia coming ashore in the Big Bend area of Florida this week, first time for that area of the state since 1896. Winds over 80 mph were measured in several places, with storm surge water inundating many roads. Some areas reported 5 to 6 inches of rainfall as well.

The Joint Typhoon Warning Center was carefully tracking Typhoon Saola in the Western Pacific Ocean this week. It was a powerful storm with winds up to 140 mph and sea wave heights over 45 feet. The typhoon is expected to come ashore near Hong Kong on Friday and bring from 10 to 15 inches of rainfall over the Friday-Saturday period.

A recent research paper published this week in the journal Nature shows that recent changes in precipitation variability and extremes across the Eastern Pacific Ocean Intertropical Convergence Zone, northern South America, and mid-latitude storm tracks are indeed closely tied to climate change. The authors used a model technique called deep learning to evaluate their hypothesis.

MPR listener question:

Now that the three summer months (June-August) are over, can you say roughly how the summer rainfall for the state ranked historically?

Answer:

On a statewide basis the average total summer rainfall this year was about 7.20 inches for the three months. For statewide data this ranks as the 5th driest summer in history back to 1895. The only drier summers were 1936, 1910, 1933, and 1929. One further note: the cooperative climate observer at Austin (Mower County) has reported only 3.80 inches of rainfall for the summer. This would be their driest summer of record there.

Twin Cities Almanac for September 1st:

The average MSP high temperature for this date is 78 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 60 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 1st:

MSP records for this date: highest daily maximum temperature of 97 degrees F in 1913; lowest daily maximum temperature of 59 degrees F in 1951; lowest daily minimum temperature of 36 degrees F in 1974; highest daily minimum temperature of 74 degrees F in 1937; record precipitation of 3.29 inches in 1942. No snowfall on this date.

Average dew point for September 1st is 56°F; the maximum dew point on this date is 75°F in 1997; and the minimum dew point on this date is 30 degrees F in 1946.

All-time state records for September 1st:

The state record high temperature for this date is 101 degrees F at Beardsley (Big Stone County) in 1913. The state record low temperature for this date is 23 degrees F at Tower (St Louis County) in 1974. The state record precipitation for this date is 7.70 inches at Nett Lake (St Louis County) in 1973. No snowfall has been reported on this date.

Past Weather:

On this date in 1894 one of the worst fire tragedies in Minnesota history occurred. Following an extremely dry, hot summer (temperatures as high as 110 F in July), prairie and forest fires become common in late August. On September 1st a fire started near Lake Mille Lacs and spread east, turning into a rapidly moving firestorm it destroyed the towns of Hinckley and Sandstone, as well as 500 square miles of forest. Over 400 lives were lost. Smoke plumes obstructed visibility on Lake Superior.

September 1st in 1913 brought afternoon temperatures in the 90s to most locations in Minnesota. Portions of Goodhue, Lyon, Mower, Big Stone, and Winona Counties hit 100°F.

Slow-moving, but strong thunderstorms brought heavy rains to portions of northern Minnesota on September 1st of 1973. Many areas reported over 5 inches of rain, while portions of Mahnomen and St Louis Counties reported over 7 inches, all time records for a daily rainfall in September.

A very cold September 1st morning in northern Minnesota in 1974 brought morning temperatures in the 20s F to 9 counties. Widespread frosts occurred in both northern and central Minnesota counties. The daytime high at Baudette only made it to 54°F.

Outlook:

Very warm over the weekend and into Monday with some record-setting high temperatures possible in some areas of the state. A chance of showers and thunderstorms by Tuesday, then significantly cooler temperatures for the balance of next week and mostly dry.