While the overall average St. Cloud September temperature (62.4°F, 3.8°F above average) did not equal the August average (64.6°F, 3.2°F cooler than average), much of the weather during September was more summerlike. 22nd warmest September (2004, 2013, 2015 warmer) 2015 was tied for the 4th warmest in St. Cloud records. There were two September days (88 on September 14; 89 on September 22) that were warmer than any August day (warmest: 86 degrees on August 1). There were a total of 10 days with a high of at least 80 degrees, but only 6 days in August. Four sticky nights had a low milder than 60 degrees, including September 22, when the low was 70 degrees. This was the first St. Cloud low temperature of 70 degrees or warmer since September 5, 2015 and only the second such mild low over the past 3 years. On September 22, the 70°F low and the 80°F average temperature each set September 22 daily records. The warmth around September 21-24 produced the latest run of three straight 90-degree highs in Minneapolis-St. Paul as well as a significant part of the rainfall.

There were no freezing temperatures in St. Cloud through the end of the month. Only north central and northeastern Minnesota had recorded temperatures of 32 degrees or colder at least once (see date of first 2017 frost from Midwest Regional Climate Center). The last 32 degree temperature in St. Cloud was set on May 1, so there have been 153 frost-free days in the St. Cloud growing season so far. The first frost is now later than more than 70 percent of the last 30 growing seasons. Only 20 percent of the growing seasons has had at 150 frost-free days. As long as the forecast heavy rain develops tonight, St. Cloud is unlikely to see any frost until at least the second week of October.

While September began on the dry side, the previous slow-moving front ended up producing fairly heavy rainfall. The St. Cloud Airport had 2.93 inches of rain, still 0.53 inch below average. All but 0.18 inch fell after September 14 and 2.54 inches fell from September 20 on. There was much more rain just to the north and west of St. Cloud with many areas over 5 inches for the month ( red colors on September rainfall chart from the National Weather Service). The rain in northwestern and west central Minnesota was important in helping to ease the summerlong drought conditions in northwestern Minnesota. The eastern Dakotas also got help in September, but much more rain is needed further to the west.

October has the potential to begin with a major rainfall in central Minnesota, which could drop as much if not more rainfall as during all of September in St. Cloud.

SThe relentless rain that produced the 2nd wettest August and the 5th rainiest summer in St. Cloud records slowed at least for a time during the first half of September. "Only" 5 days during the first two weeks of September produced measurable rain in St. Cloud. Rain and storms became a lot more frequent through the second half of the month, but the heaviest rainfall took more than one day to fall (see NWS September daily statistics for St. Cloud). While St. Cloud ended up with 1.44 inches from the slow-moving storm on September 21-25, the rainfall totals were lower than the huge amounts seen in the northern and northwestern suburbs of Minneapolis and across south central and southeeastern Minnesota. Because of these near misses, the St. Cloud Regional Airport ended up with a below average monthly rainfall total. The September amount was 3.08 inches, 0.38 inch below average. This was the first month with below average rainfall since June. Still, the huge rainfall from July on has produced a growing season (April 1-September 30) with 25.46 inches of rain, nearly five and a half inches above average. Most of central and southern Minnesota have had between 110 and 200% of the average growing season rainfall.

More Than Enough Rain for the Entire Year

With another inch of rain in early October, St. Cloud now has topped above the average precipitation for the entire year with 28.37 inches (4.93 inches above average through October 4). The annual average rainfall is 27.73 inches. And, St. Cloud has missed some of the locally heavier rainfall. Much of Stearns County has had more than 30 inches of rain this year with Mora and Moose Lake and the eastern Twin Cities Metro with 35-40 inches so far this year and south central and southeastern Minnesota having 35-50 inches of rain (see year-to-date precipitation from the National Weather Service).

Still, St. Cloud has now had 104 days with measurable rainfall. The annual average is 97 days. An average number of precipitation days for the rest of the year will push the total into the 120's, high enough to crack the 15 years with the most frequent rainfall.

September Warmth Could Lead to a Top 20 Warmest Year

The drier weather was accompanied by persistent warmth. The average September temperature was 61.7°F, 3.1°F above average. This resumed the tendency for above normal temperatures that was persistent through the winter ( 8th warmest winter last year) and part of the spring. If temperatures merely remained average for the last three months of the year, the 2016 average St. Cloud temperature would be 44.8°F, which would rank as the 14th warmest year in St. Cloud records and 0.2°F short of breaking into the 10 warmest years in St. Cloud.

Through October 4, there still hasn't been a frost in St. Cloud. The coolest temperature was 39 degrees on September 14, a morning during which some of the Brainerd Lakes saw their first frost. The first chance of frost could be on Saturday, October 8. That would put the first frost in the 90% percentile or among the latest 10% of years in St. Cloud records. The last frost of the spring was on May 15, so the growing season would be at least 145 days long.

     September 2017 Statistics

The low rainfall is quite evident in the river level reports issued this week. The weekly DNR map shows streamflow in the lowest 10% from St. Cloud through most of Sherburne and Benton Counties . Currently, the Mississippi River level at St. Cloud is 4.17 feet, among the 5 lowest stages seen at this gauge (note that the third lowest levels were seen in September 2007 , which isn't listed in the records). The Sauk River in Waite Park is down to only 1.17 feet, the sixth lowest stage seen on that river. ( In August 2007 , the Sauk River was down to 0.37 feet) The streamflow from the USGS shows that the Mississippi River basin is now below the 25% mark in the Mississippi River basin at most stations from Aitkin to the Twin Cities, in the St. Croix basin, and in the central and lower Minnesota River basin. Stream flow is now in the lowest 10% in north central Minnesota, including the Duluth, Grand Rapids, and Ely areas.

Meanwhile, temperature data shows that this September is the summer we didn't have. So far , St. Cloud is working on the warmest September in more than 70 years. Through yesterday, the average St. Cloud temperature has been 65.5°F, 7.1°F warmer than normal. If we remained this warm, this September would be the third warmest September in St. Cloud records and the warmest since 1931.