Minnesota WeatherTalk

Preliminary climate summary for September: Like most months of 2016 September was warmer than normal. Most observers report a mean monthly temperature that is 2 to 4 degrees F warmer than normal. On a statewide basis September of 2016 will be among the 15 percent warmest in history back to 1895. This follows a trend towards warm Septembers, as last year produced the warmest September in state history, while 2004, 2005, 2009, and 2013 were among the warmest ten Septembers in history as well. Extreme values of temperature for the month were 94 degrees F at Amboy (Blue Earth County) on the 21st and just 29 degrees F at several locations in northern Minnesota on the 14th.

The month of September was moderately wetter than normal in the north and very much wetter than normal in southern Minnesota, where some observers reported rainfall that was 4X or 5X times normal. Most observers reported rainfall on at least half of the days of the month. Some of the rains came in heavy thunderstor…

More heavy rain and flooding: Thunderstorms, some severe, brought heavy rainfall again to portions of central and southern Minnesota over September 21-22 (Wed-Thu) this week. Many observers reported from 1 to 2 inches, and several places reported new record daily amounts up to 5 to 8 inches. Dew points spiked in the low 70s F at a number of locations just ahead of the storm indicating that there was a very high water vapor content. Preliminary data suggest that a new statewide record daily rainfall occurred on September 22nd (old record 4.84 inches at Cambridge in 1968), but the final say on the new record will come from the Minnesota State Climatology Office. Many communities reported flash flooding, including washed out roads and culverts, and some flooded basements.

Some of the new record daily amounts of rainfall included:

7.64" at Waseca
5.15" at Wells
4.11" at Rochester
4.06" at Bricelyn
3.81" at Preston
3.74" at Spring Grove
3.70" at Zum…

A Taste of Autumn Weather the Second Full Week of September: The first taste of autumn weather appeared this week with low relative humidity and overnight temperatures in the 30s and 40s F, especially over September 13-15. Many communities in western and northern Minnesota reported overnight lows in the 30s F and a number of places reported frosts, including:

31°F at Cass Lake (Cass County)
29°F at Brimson (St Louis County)
31°F at Cotton (St Louis County)
29°F at Embarrass (St Louis County)
32°F at Orr (St Louis County)
30°F at Hibbing (St Louis County)

It was 39°F as far south as Lake Wilson (Murray County).

Humidity exhibited a roller coaster pattern this week with readings from 70 to 90 percent earlier in the week, falling off to 20 to 30 percent during the middle of the week. The cooler and drier air was having its effects on native vegetation as the autumn color changes were beginning to appear more abundantly in northern and western counties. Remember you can track fall c…

Wet Start to September: After a wetter than normal July and August, September is following trend and beginning wetter than normal for many areas of the state thanks in large part to some strong thunderstorms that crossed the state over September 4-7. Several areas of the state have reported over 2 inches of rainfall so far this month. Many climate stations are already reporting rainfall totals which are near the monthly average for September, and some locations have already surpassed the monthly normal rainfall values. A partial list of these locations:

Mabel (Fillmore County) 5.54"
Caledonia (Houston County) 4.69"
Spring Valley (Fillmore County) 4.14"
Spring Grove (Houston County) 4.03"
Lanesboro (Fillmore County) 3.40"
Worthington (Nobles County) 2.86"
Wright (Carlton County) 3.93"
Brainerd (Crow Wing County) 2.90"
Ottertail (Otter Tail County) 2.52"
Eveleth (St Lous County) 3.20"
Pokegama Dam (Itasca County) 3.52"
Ada (Norm…

Average temperatures for August from observers around the state were generally warmer than normal by 1 to 2 degrees F. The hottest periods during the month were over the first ten days, when daily Heat Index values soared above 100°F in several locations. Marshall (Lyon County) reported the highest temperature for the state on the 10th with a reading of 96°F. The lowest temperature for the month was just 37°F at International Falls on the 21st. For the first 8 months of 2016 temperatures have consistently been warmer than normal in Minnesota, placing this period as the 6th warmest in state history.

The monthly total rainfall was above normal for most places in the state, except for a few isolated pockets of dryness. Many climate observers reported total monthly rainfall that was 2-3 times normal, and on a statewide basis it was the 3rd wettest August in history and wettest since 1980. For many communities it was a near-record or record wet August. Some examples include:

11.85 inc…