Despite rainfall being above average in central Minnesota, it s slowed its pace just a bit for the second straight month. September 2014 rainfall at the St. Cloud Regional Airport totalled 4.06 inches, 0.60 inch above average. Still, the pace of rainfall is among the five highest. For the growing season (since April 1), the total is 29.72 inches, 9.47 inches above average and the 5th wettest Apr-Sept total on record. For the calendar year through September, St. Cloud has received 33.43 inches of precipitation, 10.39 inches above average. This ranks as St. Cloud's fourth wettest January through September of the 122 years on record.

Nearly three-quarters (72%) of the September rain fell during the morning and midday of September 3. A relatively narrow rainband developed between the Twin Cities and pushed across St. Augusta and the southern portion of St. Cloud. The St. Cloud Airport got 2.94 inches of rain from this storm, nearly double the old September 3 record of 1.61 inch, set in 2006. 2.70 inches fell in just one hour. This was also the St. Cloud Airport's largest single storm rainfall since 4-5 October 2005 (4.07 inches).

With additional rainfall to begin October, the St. Cloud precipitation through October 2 now stands at 33.71 inches. If this was the final rainfall total for the year, it would be the 16th wettest year on record at 5.98 inches above average.

The rainy conditions also helped to contribute to a "wait-a-minute" temperature month. There were wild swings between chilly days (3 straight days more than 10 degrees cooler than average) and very warm days (6 days at least 10 degrees above average, including 5 straight days). The month ended up averaging 61.9°F, 2.6°F above normal. The persistently humid conditions, especially early and late in the month, contributed to the average low temperature being 50.4°F, 3.6°F above normal. This was the 20th warmest September average low on record. In contrast, the September high temperature averaged 72.0°F, 1.9°F above normal. This continues the trend of warm lows seen through much of the summer.

The largest contrast was between the 4 straight days with a high of at least 80°F September 25-28 and the three straight days with a high in the 50's September 10-12. The late September warm period marked the longest streak of 80+ highs later than September 15 since 2011. That 4-day 80+ streak occurred on October 3-7. The last time there were 4 straight days actually in the second half of September was September 16-19 or 1998.

The three straight cold days earlier in the month made the first streak of sub-60 highs in the first half of September since 1986 (September 13-15). The last time there was any streak of three straight sub-60 degree highs was September 14-16, 2011 (yes, that was just three weeks before 5 straight 80-degree days in October that year).

There was fairly widespread frost in central Minnesota on September 13, including in many parts of the city. However, the St. Cloud Airport never got colder than 33 degrees that morning. If the Airport had dropped another degree, this frost would have been ranked among the earliest 10% of first frosts. However, there were no other days when the temperature approached the freezing mark, so St. Cloud's likely first frost will hold off until Saturday (Oct 4), which would rank right about average. The early frost did damage some of the corn crop, but conditions widely varied.

The cause of some of the extremes was one strong surges of northwest-to-southeast steering winds that brought really chilly air from central Canada into central Minnesota around September 9-15. This separated two periods of southwest-to-northeast steering winds, one the first week of the month, and the second after the last cool push moved out of the state. At times, high temperatures were tempered, even in the warm pattern, by lot of persistent clouds, even if there wasn't much rainfall. However, that accounts for the long stretches of mild lows (lows of 55 degrees or higher on 13 days).

The northwest-to-southeast flow pattern is reasserting itself in early October, with a strong cold push likely to produce additional frosts and perhaps a hard freeze in the first week of October.

    September 2014 Statistics