September 2003 Saint Cloud Weather Summary

     September 2003 was an outrageous weather month that defies desciption by the overall statistics. Included in the weather madness were:

• Days in the first half of the month with highs hotter than mid-July
• Days near the end of the month as cold as the middle of November.
• As many 90-degree highs as frosty mornings
• More than a whole month's rainfall in two days
• Dryness the rest of the month, producing lingering problems with low stream flow, lake levels, and their effect on crops, foliage, and lawns.

    Because of the wild variations of extremes in September, the numbers for the month don't really tell the story, but let's get them out of the way. The September average temperature was 58.6°F, 1.2°F warmer than normal. The total rainfall for September was 3.94 inches, more than an inch above normal.

     So, what temperature statistics can document our wild swing from summer weather to early winter? The transition happened on September 19 (see daily September statistics). For the first 18 days of the month, Saint Cloud had an average high temperature of 79.6°F and an average low of 50.5°F. This average high temperature was typical of middle August (see August daily normals). On September 6-8, Saint Cloud had its first September heat wave (3 consecutive days with a high of at least 90°F) since September 1978. Conversely, during September 19-30, Saint Cloud had an average high of 59.3°F and an average low of 38.4°F. These average temperatures were typical of mid-October (see October daily normals). The weather of the last week (highs in the middle 50's and lows in the upper 20's to lower 30's) are typical of the first week in November (see November daily normals). There were three days with low temperatures at or below freezing. The first frost was on September 25, only one day earlier than average, but surprising considering conditions earlier in the month.

     Were this September's roller-coaster temperatures unusual? It is not that unusual to have a spring or fall month with both 90°F highs and 32°F lows. In recent years, September 1998, May 2000, and May 2002 had both extremes. However, it is highly unusual to have so many days of each. The last time that Saint Cloud experienced at least three 90°F highs and three 32°F lows in the same month was September 1976. By the way, that September was even more extreme than this one, with 10 90°F highs and 6 32°F lows.

    Part of the reason for the extremes were the dry conditions which have plagued Minnesota since mid-July. Since dry soil heats up and cools down more easily than wet soil or puddles, the soil conditions helped to allow warm air masses to generate warmer temperatures and cold air masses generate colder temperatures. Of course, the steering wind shift changes. During the first two-thirds of the month, the upper-level winds primarily blew from west to southwest flow, bringing air that had descended the east slopes of the Rockies into the Dakotas and Minnesota. However, the same pesky high pressure system that kept cool air flowing for much of the late winter and early spring from last season set up again. Yesterday, highs were in the 60's in central Alaska, but only made it to the lower 50's in central Minnesota.

    Yes, we got above normal rainfall this past month, but the delivery of the rain did not help all of our problems from the late summer dry period. Of the 3.94 inches that fell in September, 3.45 inches fell on September 10-12 as a slow-moving cold front allowed repeated bands of thunderstorms to move over central Minnesota. There were 2.56 inches of rain on the 11th alone. This was the 5th rainfall event of at least an inch during 2003, which has already equalled the annual average (historic 1-inch rainfalls here), but this wasn't enough rain to break the daily rainfall record for the 12th (3.35 inches in 1980), nor equal the 4.39 inches that Saint Cloud picked up in about 8 hours on September 5-6 of last year. The heavy rainfall helped to ease a serious dry period, as noted by the Minnesota State Climatologist's Report on the dry middle and late summer. Despite the heavy mid-September rainfall, Saint Cloud's rainfall since July 15 is still nearly three and a third inches below normal.(see precipitation statistics below). The dry conditions are shown in the National Drought Monitor for September 23 as moderate drought covers the southern three-quarters of the state with severe drought in west central Minnesota. This is also being reflected in low stream and river flow in the area.

     The prospects for warmer weather and more rain are uncertain. With the British Columbia high locked into place, high temperatures will continue to be 10-20 degrees below normal through early next week with a brief break tomorrow. Lows will mostly remain in the 20's and 30's, which is also 10-15 degrees below normal. Beyond that, the high should break down, allowing milder air into Minnesota. Is this a recurring pattern that will shape much of the cold season to come? That I can't say right now.

    September 2003 Statistics