July 2010 Saint Cloud Weather Summary

Ordinary July Statistically, But Not by Severe Weather

Saint Cloud Weather Summary for July 2010    

The July statistics from the Saint Cloud Regional Airport showed an ordinary month, but the amount of severe weather across Minnesota was far from ordinary.

The average temperature at the Saint Cloud Regional Airport was 72.2°F, 2.4°F warmer than normal. The rainfall at the St. Cloud Airport was 3.15 inches, 0.19 inch below normal.

Severe Weather Dominated Mid-June Through the End of July

37 tornadoes touched down in Minnesota between June 17 and July 17. In a normal year, 25.8 tornadoes are recorded in Minnesota. The most tornadoes in a calendar month was 38 tornadoes in June 2001. The worst outbreak, however, was still June 17, when 20 tornadoes touched down, including 4 rated EF-4, for the first time in Minnesota.

On July 17, there were four brief tornadoes in Minnesota. More importantly, golf-ball to baseball-sized hail hit much of central Minnesota, especially in Cold Spring and Richmond, and wind gusts as high as 76 MPH in Monticello and 62 MPH in Sauk Centre were recorded. Also, there was more than 2 inches of rain in Hillman in 30 minutes.

On July 27, central Minnesota was hit by wind damage with wind gusts of 71 MPH at the Veterans Golf Course in St. Cloud and 67 MPH in Sauk Centre. But the worst damage occurred in northwestern and north central Wisconsin. Six Wisconsin tornadoes have now been confirmed, including the first seen in Iron County in 40 years. Three people were injured in the wilderness around the Turtle Flambeau Flowage.

Finally, during the storms on July 23, a record 8-inch hail stone fell in nearby Vivian, South Dakota, near Pierre. The record stone was 8 inches across along its longest length and weighed nearly 2 pounds. It was nearly twice the size of the worst hailstones to hit Cold Spring on July 17.

The reason for the persistent areas of thunderstorms across Minnesota is that the state has mostly been crossed by the main belt of steering winds in the past 6 weeks, according to the National Weather Service in the Twin Cities graphic. During late June, the steering winds were southwesterly, leaving us to the north of the hot and steamy air in the central Plains, but close enough for us to tap this air and generate severe thunderstorms. In mid-July, the heat had pushed into central and southern Minnesota, pushing the main swath of severe weather across central Minnesota.

Frequent Thunderstorms Produced Widely Varying Rainfall

Rainfall, however, widely varied across the Minnesota and even the central Minnesota area due to the spotty nature of thunderstorms. There was a relative minimum of rainfall from Redwood Falls, Granite Falls, Willmar, and Litchfield through St. Augusta, Paynesville, St. Cloud and the St. Cloud Airport into Clear Lake and Foley. There was less than three and half inches of rain throughout this area. Further to the north, rainfall was above normal and topped out with more than 7 inches in the Detroit Lakes-Park Rapids area. It was the second rainiest July in International Falls with 8.81 inches of rain. There were also more than 10 inches of rain in most of northern Iowa, southwestern Wisconsin, and eastern South Dakota due to the persistent storm track.

Thunderstorms are not usually an efficient method of spreading rainfall over a large area that is short on moisture. The heavy rainfall, at best, tends to fall in bands perhaps 25 miles wide, leaving areas on either side relatively dry.

This leaves a swath of Minnesota substantially short on rainfall for the current growing season. The worst shortage is in northeastern Minnesota, which has been ranked in being under severe drought conditions for most of the season. However, the dry area continues in a swath from the Arrowhead through the Iron Range, Aitkin, Brainerd, the north end of Lake Mille Lacs, then through Morrison and Stearns Counties and Paynesville, then westward through Morris, Benson, Montevideo to Ortonville and Wheaton. In the Little Falls and St. Cloud areas, rainfall is on the order of 1-2 inches below normal, although the St. Cloud Airport is about two and quarter inches below normal on rainfall since March 12 (11.58 inches fallen; 13.79 inches normal).

July Consistently Warm, But Not Hot

July temperatures were consistently warm, but not on a record pace. There were only 4 days with a high of at least 90 degrees, none of them warmer than the 94 degrees recorded on May 24. On the average, St. Cloud has 4.67 July days with a high of at least 90. July 2010 was substantially warmer than the past three Julys, especially warmer than July 2009, which was the third coolest July in St. Cloud records. Still, it was a good two degrees cooler than any of the 10 warmest Julys, the most recent one being in July 2006, 8th warmest July on record.

The remarkable part of July 2010 was the consistent warmth. Highs broke 80 degrees on 28 of the 31 days. Only 6 previous Julys, the last one in 2006, had more highs of at least 80. The only July where the high broke 80 degrees every day was in 1916.

Having frequent highs in the 80's means that St. Cloud has often found itself along or on the warm side of the steering winds. Cool air intrusions from northern Canada have not happened. However, the frequent clouds left by thunderstorms moving over the area or passing nearby have kept us from climbing to 90 and above more frequently.

Duluth did manage to tie a record by breaking 70 degrees for a high every day in July. This has only happened one other time, in July 1988. This can be attributed to the weather pattern keeping lake breezes limited to further up the North Shore. It may also be related that the Lake Superior water temperatures are much warmer than normal, thanks to the early spring snow melt and Duluth's warmest spring in history.

The persistently warm weather with frequent rainfall has been generally good for crops. As of July 26, 85% of the corn crop was at or beyond the silking stage and other small grains were being harvested. Unfortunately, the frequent severe weather has produced crop damage due to hail.

August Starting Off A Bit Drier and Cooling Later in the Week

It appears that the main steering wind pattern will produce some chances of rain over central Minnesota during the first few days of August, but the bulk of the rainfall will likely be held over the south. During the second half of the week, a rare intrusion of cooler, central Canada air will take the humidity out and knock high temperatures out of the 80's for a day or two. The next best chance of severe weather over central Minnesota will not come earlier than the second half of the weekend.

    July 2010 Statistics