FROM: Bob Weisman

Earth Sciences, St. Cloud State University

After a cool, dry spring, the weather switch turned in Saint Cloud, producing a warm, humid and rainy June. The average temperature at the Saint Cloud Regional Airport was 68.5 degrees, 3.4 degrees above normal. However, this only ties 1963 for the 20th warmest June on record. This was the warmest June since 1988, which had an average temperature of 71.1 degrees. The warmest June in the 122 years of Saint Cloud temperature records was 1933 with an average temperature of 75.1 degrees.

There were no record warm temperatures set during the month, and there were only 2 days with a high of at least 90 degrees, about normal for the month. In fact, most of the warmth in June was the result of the average low temperature being more than 5 degrees above normal. There were 15 days with a low of at least 60 degrees, including the last 12 days of the month. Also, the last two days of the month had lows of at least 70 degrees. The average number of 70-degree lows for the year is a little more than 3 and we had two days already. On June 30, the low was 75 degrees, only the 50th day in 107 years that the low was 75 degrees or above. There have been only 8 years in which there have been two days with a low of 75 degrees or higher. So, the warm low temperatures have been very unusual.

It was also a very wet month, but not as wet as other areas. The monthly precipitation was 4.92 inches, nearly half an inch above normal. June included two days with over 1.4 inches of rainfall on the 21st and the 24th. The period from June 18th through June 24th produced 3.58 inches, more than 70% of the monthly total. The heavy rainfall on the 24th fell in a little more than an hour, producing flash flooding in the city.

How do we change from below normal spring weather to alternating heat and thunderstorms? The whole Central US weather pattern changed as heat built in the Southern Plains and moved to the Mountain West for the end of the month. This is the same system producing the heat and dry weather that has made the Western fires harder to control. Minnesota has spent the last 2/3 of June near the frontal zone that has separated the heat and humidity from slightly cooler and drier Canadian air. Just to the north of the front, the heat wave air moves over the front, especially at night, producing large slow-moving thunderstorms that can produce tornadoes, hail, and high winds, but also produce flooding rains since they are slow-moving. Or when the front stalls, thunderstorms go over the same area night after night.

So, during the 19th through the 24th, the front dropped to our south. So, we had highs in the low 80’s, but nightly thunderstorms. This round of rain also produced the second wave of flooding rains in northwestern Minnesota, including Mahnomen and Ada (for the second time in two weeks). During the 9th and 10th, the front pushed to our north, so we missed all the thunderstorms, except when the cold front came through. However, northwestern Minnesota, on the cool side of the front, got 6-14 inch rainfalls that produced the first round of flooding this month. On the other hand, from June 25th through the end of the month, the front pushed to our north. So, we got the heat and nearly cloudless skies while the thunderstorms were limited to northwestern Minnesota or even southern Ontario and Manitoba.

Compared to much of the rest of the state, the June rainfall in Saint Cloud was low for a few reasons. First, the city just missed some severe rainfall. The slow-moving thunderstorms on the 24th produced up to 8 inches of rainfall in parts of Wright County. Portions of Hwys. 25 and 12 were closed for several days as portions of the roads washed out. From Saint Cloud westward, rainfall totals were lower than areas to our north and south.

However, some of the lower rainfall total may be due to instrument problems. The automated rain gauge is suspected of not being able to keep up with high rainfall rates. The most glaring example was on June 24. While the Saint Cloud Airport rain gauge measured 1.10 inches of rain from the afternoon thunderstorms, the manual rain gauge at Saint Cloud State University, 4 miles away from the airport gauge, recorded 1.65 inches. The total June rainfall at SCSU was 6.29 inches, 1.37 inches more than the airport. Some of the difference is probably a result of the thunderstorms, which can produce widely varying amounts of rain over a relatively small area. However, when the radar coverage was similar, like on the afternoon of the 24th, the accuracy of the instruments must be questioned.

The turnaround from a cool, dry spring to a hot and wet June again illustrates the dangers of long-range weather forecasting. Statistics show that seasonal forecasts are, in general, not good. However, the summer weather, dependent on small weather systems and thunderstorm complexes, is the season that is the hardest to predict. So, don’t ask me what a humid, rainy June means for the rest of the summer. The only sure thing is that it means a bumper crop of mosquitoes.

JUNE STATISTICS                  JUNE 2002              NORMAL
TEMPERATURE (oF)
Average high temp                78.7                   77.3
Average low temp                 58.2                   52.9
Average temp                     68.5                   65.1
Number of days with 90+ high      2                      2.2
Hottest high temp for the month  95 on the 30th
Coolest high temp for the month  53 on the 3rd 
Warmest low temp for the month   75 on the 30th 
Coolest low temp for the month   41 on the 5th 
Records set: none

PRECIPITATION (IN)              JUNE 2002              NORMAL
Total for month                 4.92                   4.51
Maximum daily amount            1.45 on the 21st
Growing season total(1 Apr-30 Jun)10.35                9.81

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