July Climate Summary:
It was warm and wet for the month of July across most of Minnesota. Statewide July of 2020 was both the 14th warmest and 14th wettest in history back to 1895.
Average monthly temperatures from the state climate network ranged from 1 to 4 degrees F warmer than normal. There were 25 daily high maximum temperature records tied or broken and 38 daily high (warm) minimum temperature records tied or broken with the state climate station network. Extremes for the month ranged from 97°F at a number of locations on the 3rd to just 40° at Brimson (St Louis County) on the 23rd. With extremely high dew points (many days produced a dew point of 70°F or greater) the National Weather Service had to issue Heat Advisories and Excessive Heat Warnings on a number of days as the Heat Index soared to 100 degrees F or greater. Interestingly enough Hallock (Kittson County) in extreme northwestern Minnesota reported one of the highest Heat Index values with 107°F on the 25th.
Rainfall around the state was generally above normal thanks to some very heavy thunderstorms. Portions of at least 15 counties reported monthly rainfall totals of 8 inches or more. For Kittson County in far northwestern Minnesota it was the wettest July in history with Karlstad reporting 10.11 inches of rainfall. Suffice to say that small grain harvest was delayed there. Also over July 25-26 a rare mega-storm occurred over portions of Sibley, Renville, Le Sueur, Nicollet, Waseca, Blue Earth and Rice Counties dropping 6 inches or more over 1000 square miles. Many flash floods were reported from this storm. It was analyzed by the DNR State Climatology Office.
The storm produced over 10 inches of rain in a few locations and was the first mega-storm to occur in the state since 2016.
Across the state climate network 38 daily rainfall records were either tied or broken, including a new all-time statewide 24-hour record for July 26th of 8.63 inches at Mankato 2.9 SSW in Blue Earth County.
In portions of Fillmore and Winona Counties climate observers actually reported below normal July rainfall, something that is very rare for them in recent years. And some small pockets of moderate drought remained at the end of the month in west-central and northern Minnesota.
Unfortunately, severe thunderstorms produced tornadoes in Grant and Otter Tail Counties on July 8th. One fatality (the first from a tornado since 2011) was reported near Dalton, MN.
Weekly Weather Potpourri:
The NOAA National Hurricane Center is tracking Tropical Storm Isaais (ees-ah-EE-ahs) this week. It is expected to strengthen into a hurricane and perhaps track off the east coast of Florida this weekend and towards the east coast of North Carolina Hopefully it will remain far enough out to sea so as not to force any evacuations of coastal communities, but it will likely bring some heavy rains.
A recent paper in Climate and Atmospheric Science documents the wetter climate of Alaska and how it is affecting the permafrost there. The increased rainfall is leading to a deeper summer thawing of the permafrost which is changing the structure and composition of ecosystems. Long term this may increase the risk of more wildfires there. You can read more from the Science Daily web site.
This week’s AGU-EOS Bulletin highlights an article from India’s first assessment of climate change. It discusses how climate change has hastened glacial melting across the Hindu Kush Himalaya region, home to some of the world’s tallest peaks, including Mount Everest. This pace of change will have dramatic consequences on India’s freshwater resources.
MPR listener question:
To my eyes, the sky was bluer in April than I had ever noticed before. It seems less deep blue now. Is that true? How is sky color measured?Answer:
Indeed, many Minnesota citizens commented earlier in the current pandemic episode about the sky being so blue. Certainly, it is likely that both reduced airline traffic and vehicle traffic may have had something to do with this. But as spring and summer progressed more and more water vapor (evaporation), dust, and aerosols were released into the atmosphere and diminished the measurement of “atmospheric transmissivity.” This is a scientific way of saying that more of the solar radiation (energy from the sun) was scattered by a dirtier atmosphere. The happens normally with the summer season, but was especially observable thanks to the pandemic reducing our human activities that lead to greater emissions of dust, gases, and aerosols into the atmosphere.BTW I am not aware of any measurement that is specifically focused on the “blueness” of the sky. Perhaps someone has developed Munsell charts (color codes using Hue, Value, and Chroma) for the sky similar to the ones used to assess the color of soil or vegetation.
Twin Cities Almanac for July 31st:
The average MSP high temperature for this date is 83 degrees F (plus or minus 6 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 31st:
MSP records for this date include: highest daily maximum temperature of 105 degrees F in 1988; lowest daily maximum temperature of 68 degrees F in 1898; lowest daily minimum temperature of 47 degrees F in 1924; highest daily minimum temperature of 80 degrees F in 2006; record precipitation of 0.79 inches in 1911. No snowfall has been reported on this date.
Average dew point for July 31st is 60°F; the maximum dew point on this date is 78°F in 1987; and the minimum dew point on this date is 39°F in 1936.
All-time state records for July 31st:
The state record high temperature for this date is 110 degrees F at Madison (Lac Qui Parle County) in 1988. The state record low temperature for this date is 31 degrees F at Sawbill Camp (Cook County) in 1937. The state record precipitation for this date is 6.70 inches at Albert Lea (Freeborn County) in 1961. No snowfall has been reported on this date.
Past Weather Features:
Cold camping in the northland back on July31, 1903. Many parts of northern Minnesota reported morning low temperatures in the 30s F. It was just 32°F in parts of Roseau and Itasca Counties.
Strong thunderstorms brought heavy rains to the state on July 31, 1953. Southwester Minnesota was hit with hail and 2-4 inches of rain. Some roads were washed out and harvesting of wheat and oats was disrupted.
July 31, 1988 saw many record-setting daily high temperatures across Minnesota. High temperatures ranged from 100° to 110° across portions of 40 counties in the state. The nighttime temperature never fell below 80° at New London (Kandiyohi County).
Outlook:
Near seasonal temperatures on Saturday but with chances for showers and thunderstorms. Then much cooler than normal for Sunday through Wednesday. Generally dry through the period. There will be another chance for rain by next Thursday.
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