Strong Warming Trend in September:
Despite a rather cool, dry start to this month of September, it is worth noting what a strong warming trend has been measured over the last 30 Septembers in Minnesota. Since 1993 the average September temperature on a statewide basis has increased over 3.5°F. Further, 24 of the last 30 Septembers have been warmer than normal. September of 2015 was the warmest in state history, at 7°F above normal, and September of 2023 (last year) was the second warmest at 6.7°F above normal.
September rainfall has been highly variable since 1993 with most years either being very dry or very wet, and very few years being near average. For example, in both 2010 and 2019 the statewide average rainfall in September was over 6 inches, while in 2012 it was just 0.61 inches.
So what might we expect the rest of this month? After a rather cool Saturday this weekend, the balance of the month will bring mostly well above normal temperatures, with many daytime highs in the 80s F. In addition, it also appears that it will be drier than normal, perhaps promoting more garden and landscape watering than was done all summer.
Weekly Weather Potpourri:
According to the BBC and the Joint Typhoon Warning Center, Super Typhoon Yagi was expected to reach the South China coast (south of Hong Kong) by Friday and into early Saturday. It is the strongest typhoon in that area of the South China Sea in at least ten years, and has generated winds of 150 mph, with sea wave heights near 50 feet. As a category 5 storm it will likely cause serious damage to many coastal communities.
This week’s AGU-EOS news includes an interesting analysis of Europe’s recent greenhouse gas budget. Scientists found that parts of eastern Europe and northern Spain have become stronger carbon sinks because of a combination of land use changes, climate-driven disturbances, and—in the case of eastern Europe—a sizable growth of forest biomass. The analysis found that the highest emissions of these gases are found in Belgium, the Netherlands, and the southern United Kingdom.
MPR listener question:
We are relatively new arrivals to Minnesota (originally from Missouri) and we love Minnesota Public Radio. We have heard that it occasionally snows in September here. Is that correct, and if so how often?
Answer:
A September snowfall in Minnesota is perhaps a once-in-a-lifetime occurrence for residents of the southern part of the state. For example, over the past 125 years or so, there have been only 3 measurable snowfalls in the Twin Cities (most recently 1985). Though still a rare occurrence, it is more frequent in northern Minnesota. For example, in the area from Lake of the Woods over to International Falls (along the Canadian Border) there have been 12 measurable snowfalls during September over the past 125 years, most recently in 2003. So, don’t get your hopes up. It is far more realistic to expect the first snowfalls the second half of November.
Twin Cities Almanac for September 6th:
The average MSP high temperature for this date is 77 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 58 degrees F (plus or minus 7 degrees F standard deviation).
MSP Local Records for September 6th:
MSP records for this date: highest daily maximum temperature of 98 degrees F in 1922; lowest daily maximum temperature of 55 degrees F in 1911; lowest daily minimum temperature of 35 degrees F in 1885; highest daily minimum temperature of 75 degrees F in 1913, and record precipitation of 1.61 inches in 1881. No snowfall has occurred on this date.
Average dew point for September 6th is 55°F; the maximum dew point on this date is 75°F in 1970 and the minimum dew point on this date is 33 degrees F in 1956.
All-time state records for September 6th:
The state record high temperature for this date is 105 degrees F at New Ulm (Brown County) in 1922. The state record low temperature for this date is 23 degrees F at Park Rapids (Hubbard County) in 1885 and at Two Harbors (Lake County) in 2011. The state record precipitation for this date is 8.44 inches at Cloquet (Carlton County) in 1990. There has been no snowfall on this date.
Past Weather:
The warmest September 6th in state history was likely in 1922 when 37 climate stations reported afternoon temperatures of 90°F or greater. Ten counties reported temperatures of 100°F or greater and at Winona even the overnight low temperature never dropped below 80°F.
On September 6 of 1988 observers across 10 northern Minnesota counties reported frost, with temperatures in the mid to upper 20s F in many areas. The afternoon high temperature only reached 60°F at Lutsen and Bemidji that day.
Heavy thunderstorms moved across northeastern Minnesota over the evening of September 5 and into the morning of September 6 in 1990. The heaviest rains spread from Itasca County east into Carlton and St Louis Counties. The Duluth area reported over 3 inches, Floodwood reported over 6 inches of rain, Jay Cook reported over 7 inches, and Cloquet reported over 8 inches of rain. Many roads were closed due to flooding.
Outlook:
Cool start to the weekend with some morning low temperatures up north in the 30s F on Saturday, with moderation in temperatures by Sunday. Then a significant and prolonged warming trend will start and last at least a week. Temperatures will be well above normal, with many days in the 80s F. It will be generally dry all of next week.
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