Climate Summary for August

Climate Summary for August:

After a warm first half of the month when many climate stations reported record-setting warm overnight minimum temperatures, the climate moderated and most observers are reporting a mean monthly temperature that ranges from 1 to 2 degrees F warmer than normal. The extremes for the month were 99°F at Preston (Fillmore County) on the 14th, and 34°F at International Falls (Koochiching County) on the 2nd.

For August rainfall, most northern counties reported below normal totals for the month, while many central and southern counties reported above normal rainfall for the month. The heaviest rainfall events came near the beginning of the month, and then again near the end of the month. During the course of the month 28 new daily rainfall records were reported in the state climate observer network. Extreme rainfall totals for the month ranged from over 11 inches at Caledonia (Houston County) to just over 1 inch at Browns Valley (Traverse County).

The other notable weather characteristic of the month of August was that on nine days the Air Quality Index was high, posing a health risk. This was due to persistent westerly and northwesterly flow patterns that brought smoke from Canada wildfires and wildfires in the western USA states as well.

Another Round of Strong Thunderstorms:

Strong thunderstorms crossed portions of the state on Monday and Tuesday (August 27-28) of this week. There were reports of brief tornado touchdowns in Rice, Dodge, and Goodhue Counties, but far more reports (26 in all) of strong thunderstorm winds ranging from 50-80 mph that broke or toppled trees and took out power in some communities. There were also reports of large hail from Stearns and Becker Counties.

These thunderstorms dropped record-setting rainfall in many parts of Minnesota and western Wisconsin. Some of the new record amounts in Minnesota included:

1.78 inches at Preston

3.06 inches at Mora

3.19 inches at La Crescent

3.86 inches at Harmony

4.95 inches at Hokah

5.53 inches at Mabel

La Crosse, WI reported a record amount of 3.04 inches, with larger amounts of rainfall in surrounding areas. Widespread flash flooding was reported by Tuesday. More narrative about the storms can be found at the at the Minnesota State Climatology Office web site.

Weekly Weather Potpourri:

The 22nd Annual MPR Minnesota State Fair Weather Quiz which was broadcast live from the Fair on Friday, August 31, 2018 is available online to take at the MPR web site. Give it a try and test your knowledge about weather and climate.

NOAA has release online a Drought Risk Atlas that is useful to assess the risk of seasonal drought anywhere in the USA. It uses climate data up through the year 2012, a year when broad scale severe drought was widespread across the country, with over 2200 counties involved.

There is an interesting case study about building climate resilience using the city of Fort Collins, CO and the mitigation work that was done to lower the risk of flooding from the Poudre River, and coincidentally develop more green space for the city.

In the Western Pacific Ocean, very strong Typhoon Jebi is heading toward southern Japan where it is expected to bring heavy rainfall starting early next week. Jebi currently has winds up to 160 mph and is generating sea waves of 40 to 50 feet. It will likely be featured on the international news starting next week.

MPR listener question:

I have read in your book and heard you say that historically June is usually the wettest month of the year for most places in Minnesota. But recently you also said there are some places where based on climate-averages (normals) August is the wettest month of the year. Where does this happen?

Answer:

Yes, for a relatively small number of Minnesota climate stations, the wettest month of the year historically is August. These include mostly southeastern locations such as Hokah, Faribault, La Crescent, Jordan, and Grand Meadow. These areas often get their most intense thunderstorms during the month of August.

Twin Cities Almanac for August 31st:

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 59 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for August 31st:

MSP records for this date include: highest daily maximum temperature of 94 degrees F in 1907; lowest daily maximum temperature of 56 degree F in 1944; lowest daily minimum temperature of 40 degrees F in 1974; highest daily minimum temperature of 75 degrees F in 1961; record precipitation of 1.50 inches in 1914. No snowfall has occurred on this date.

Average dew point for August 31st is 57°F; the maximum dew point on this date is 75°F in 1960; and the minimum dew point on this date is 34°F in 1949.

All-time state records for August 31st:

The all-time state high temperature for today's date is 100 degrees F at Beardsley (Big Stone County) in 1898; the all-time state low for today's date is 23 degrees F at Cotton (St Louis County) in 1970. The all-time state record precipitation for this date is 5.85 inches at Crookston (Polk County) in 1908. A trace of snow fell on this date in 1949 at Duluth.

Past Weather Features:

August of 1898 ended with some very high, record-setting temperatures around Minnesota. Over 50 Minnesota cities saw temperatures climb into the 90s F. On some nights the temperature never dropped below 70 degrees F as well.

The morning of August 31, 11970 brought widespread frost to much of northern Minnesota. Frost was reported in Aitkin, Cass, St Louis, Itasca, Roseau, Beltrami, Kittson, and Carlton Counties, with some readings in the 20s F. Obviously the end of the growing season.

Strong thunderstorms delivered heavy rains to eastern parts of Minnesota over August 30-31, 1977. There was widespread flash flooding around the Twin Cities where 4-7 inches of rain fell. The Grandstand show at the State Fair was washed out.

Outlook:

A dry start to the weekend with plenty of sun on Saturday. Increasing cloudiness with a chance for rain Sunday-Tuesday, as temperatures fluctuate slightly either side of normal. Drier towards the end of next week.