September 2007 Saint Cloud Weather Summary

We came into September with the continuing rain shortfall being the main story in the northern two-thirds of Minnesota. However, St. Cloud ended up in a rainy pattern for much of the month, helping to ease the worst effects of the rain shortfall. According to the Saint Cloud Regional Airport statistics, there were 4.10 inches of rain during September, which was 1.17 inches above normal. The rainfall relief came from a much more active weather pattern with frequent Pacific storms moving directly from the West Coast into the Northern Plains. These storm systems also had access to Gulf of Mexico moisture several times.

However, the rainfall hit Minnesota in the form of thunderstorms, creating local rainfall maxima. St. Cloud did have 7 days days with at least a quarter-inch of rain but, except for a direct hit from the September 18-19 rain (1.82 inches), more rain fell elsewhere. While St. Cloud and Willmar had 1-1 1/2 inches above normal rainfall during the past 4 weeks, according to the October 1 Minnesota rainfall table from the Minnesota State Climatology Office, Collegeville, Becker, and Aitkin had rainfall that was more than 2 inches above normal, and Staples and the Twin Cities were over 3 inches of rain above normal. The storm on September 6, which produced .60 inch in Saint Cloud, produced an Iron Range Deluge, according to the Minnesota State Climatology Office, with more than 8 inches of rain in some areas.

The storm that had the biggest effect on central Minnesota was the heavy rain on September 20-21 (report from Minnesota State Climatology Office). In addition to the large tree damage in Sartell and St. Stephen, the metal roof torn off a building in Sartell, the fence damage at Golden Spike Speedway, and the straight line wind damage in the Twin Cities, including a tornado in Woodbury (see NWS Summary of severe weather), heavy and persistent thunderstorms dumped 4.85 inches in Sauk Centre between 10 AM and noon, producing flash flooding that caused all roads into town to be closed. Standing water reached a foot deep in areas in town. St. Cloud got sideswiped by this storm, only picking up .53 inch from this system.

One result of the heavy rainfall was the raising of streamflow levels from near record lows. On September 11, the Mississippi River level in St. Cloud dropped to 3.71 feet. That was .01 feet lower than it hit on August 8 and ranks as the third lowest level on record, as can be seen on the Record Mississippi River Low Flows at St. Cloud. The Sauk River had dropped back to 0.48 feet on September 17, not quite as low as the 0.39 foot level seen on August 8. The latest river stages show the Mississippi River at over 4 feet and the Sauk River at 1.4 feet.

The heavy September rainfall drastically improved the water situation in much of Minnesota. As of September 16, the St. Cloud Airport rainfall was only 6.85 inches between June 4 and September 16. This was 6.21 inches below the normal of 13.06 inches. As of the end of September, the St. Cloud Airport rainfall pushed to 10.42 inches, 3.99 inches below the normal total of 14.41 inches. For the growing season (June 1-September 30), St. Cloud's rainfall totaled 15.78 inches, 4.03 inches below the normal total of 19.81 inches. Central Minnesota just to our north remains in the severe to extreme drought category, as noted by the September 25 National Drought Monitor from the National Drought Mitigation Center. The severe drought extends from Glenwood, Alexandria, Long Prairie, and Wadena to our west through northwestern Stearns County, Staples, Little Falls, and Brainerd to Aitkin and Lake Mille Lacs. This is because of the severity of the rainfall deficit, up to 9 inches behind in some areas, before the rains came. You can really see the shrinking area of drought designation on the 12-week loop of Drought Monitors.

On September 17, the Minnesota DNR streamflow report had "red paint," signifying streamflow in the lowest 10% of years through most of northeastern, central, and east central Minnesota, including the Sauk, Mississippi, St. Croix, and rivers draining into Lake Superior. The October 1 Minnesota DNR streamflow report shows that all of the red paint is gone, with streamflow in the lowest 25% of readings (yellow area) only along the Mississippi River and tributaries from the Crow Wing River upstream to Lake Itasca.

Temperature-wise, the Saint Cloud average September temperature was 61.0°F, 3.6°F above normal. This was very warm, but not nearly as warm as September 2004 (64.1°F, 9th warmest September on record). This was the result of a summery first week of September, a chilly second week, and a mostly mild last half of the month. The first 6 days of September had highs of at least 84°F, including our second heat wave of the summer: three consecutive days with a high of at least 90°F on September 3-5. The storms that produced the Iron Range Deluge on September 6 marked a week-long change in the weather pattern that allowed air from the Yukon and Alaska to move into Minnesota during the following week. The extreme swing between the 6th (high 89°F; low 68°F) and the 8th (high 64°F; low 44°F) produced nearly 25 degree drops. From September 7 through September 16, low temperatures remained in the 40's or cooler, including our first frost on September 12th (normal first date: September 22 as seen on the St. Cloud growing season frost-freeze statistics from the Midwest Climate Center). This ranks in the earliest 10% of frost dates. We had another frost on September 14, followed by a hard freeze with a record cold low of 27°F on September 15. This also ranked in the earliest 10% of freeze dates. Normally, the first low of at least 28°F isn't reached until October 1. The high temperature only broke 70°F once.

For the second half of the month, temperatures were either near or above normal. Clouds and rain kept high temperatures from threatening record highs, but the mostly warm and humid air dominated the month. If that cold 9 days (September 7-15) were taken out, our average September temperature would have been more than 3 1/2 degrees warmer. The temperature of 64.7°F would have ranked tied with 1920 as the 5th warmest September on record.

So, what's on tap for October? The month is beginning in the milder weather pattern with a continued frequent chance of significant rainfall. Highs will be in the 70's, which is 6-15 degrees above normal for early October, with the next best chance of heavy rains over the upcoming weekend. Rainfall after the growing season ends is very efficient at making up deficits. Since the plant life has mostly stopped using water, 50% of the rain that falls can go into ground water recharge. So, a wet October would be very helpful to our situation.

    September 2007 Statistics