Early-Season Heat Waves

Note: this story will be updated every 1-2 days during early June, 2021.

Heat extremes often punctuate Minnesota's summers, and are most common from the end of June through the end of August. July is by far the state's hottest month, boasting virtually all of our statewide and station-specific heat records, and historically accounts for 40% of all 90-degree F days.

Heat waves that occur during or before the first half of June are less common, and often of a different nature than many (though not all) mid-summer heat waves. A typical July or early-August heat episode may be oppressively humid, whereas late-spring episodes tend to be somewhat "dry."

The worst heat wave on record in Minnesota occurring any time through the first half of June was from June 3 to June 10, 2021. This event demolished daily and early-season temperature records in northern Minnesota initially, and dealt record or near-record warmth to southern and central Minnesota for 8 unrelenting days, when the temperature never fell below 70 F in the Twin Cites, and when many locations soared into the 90s or even 100s each afternoon.

Following are some statistics from the Twin Cities historical record, for heat extremes occurring on or before June 15th. Keep in mind, a heat wave is not only defined by the daily high temperatures, but also by warm nights. Some of late spring and early summer's hottest days have had tolerably mild nights, thanks to the dry air in place. Any time the high tops 90 F and the low also tops 70 F, however, the body will struggle to cool itself, day or night.

 

Highest daily temperature recorded in Twin Cities on or before June 15
RankTemperature (F)DateRemarks
1106May 31, 1934Highest temperature recorded outside of July
2103June 7, 2011 
3102June 8, 1985 
4100May 28. 2018Earliest occurrence (in season) on record
-100June 13, 1956 
699June 5, 2021Most recent occurrence
-99June 13, 1987 
-99June 10, 1956 
-99May 22, 1925Earliest occurrence (in season) on record
1098May 14, 2013Earliest occurrence (in season) on record
-98June 14, 1987 
-98June 10, 1973 
-98May 30, 1934 
-98May 28, 1934 
1597June 10, 2021 
-97June 4, 2021 
-97June 6, 2011 
-97May 19, 2009 
-97May 28, 2006 

 

Number of 90 F (or greater) high temperatures through June 15 in Twin Cites
RankYearNumber of 90 F Highs
1193412
2198811
-198711
420218
-20078
-19768
720187
-19597
-19527
-19257
1119566

 

Runs of five or more consecutive days with 90+ F high temperatures, occurring on or before June 15, in Twin Cities

DatesNumber of Consecutive 90+ F DaysHighest Temperature (F)Average Daily Maximum Temperature During Streak (F)

Average Daily Mean Temperature  During Streak (F)

Remarks
June 3 - 10, 2021899

95.6

85.2Ongoing, longest and apparent hottest / warmest streak
May 24 - 29, 2018610093.581.0Earliest streak (in season) and earliest 100 F reading on record
May 28 - June 1, 198859291.273.2 
May 28 - June 2, 1934610694.082.3 
June 9 - 14, 1956610095.582.8 
June 11-15, 200759291.080.0 

 

Highest daily minimum temperature (that is, the "highest low temperature") recorded in Twin Cities on or before June 15
Temperature (F)DateRemarks
78June 5, 2021Earliest occurrence (in season) on record
78June 7, 2011 
77June 8, 2021 
77June 10, 2017 
77June 13, 1956 
76June 6, 2021 
75June 9, 2021 
75May 28, 2006Earliest occurrence (in season) on record
75May 31, 1934 
75June 5, 1925 
74June 7, 2021 
74June 8, 2020 
74May 29, 2006 
74June 11, 1956 
74June 6, 1925 
74May 22, 1921Earliest occurrence (in season) on record

 

Longest runs of consecutive low temperatures at or above 70 F recorded in Twin Cities on or before June 15 in the Twin Cities
DatesNumber of Consecutive 70+ F LowsHighest Minimum (low) Temperature (F)Average Daily Minimum Temperature During Streak (F)
June 3 - June 10, 202187874.8
June 7 - June 9, 195937371.3

 

Many of the above tables focus on "streaks" of consecutive days at or above certain temperature thresholds. However, these sorts of measures do not capture everything. One notable early-season heat wave not listed above occurred June 6 to June 14, 1976, when 8 out of 9 days produced a high of at least 90 degrees F in the Twin Cities. The average high during this period was 91.8 F, and the average daily mean temperature was 79. 1 F, meaning in many ways this event rivaled others listed above. Furthermore, it is doubtful that anyone at the time mistook the 88 F reading on June 10th for the heat "breaking!"

 

Last modified June 11, 2021