Preliminary Climate Summary for September

Preliminary Climate Summary for September:

The weather for September was remarkable for record-setting unform warmth and for highly variable rainfall.

Most climate stations reported a mean monthly temperature that is 4°F to 6°F warmer than normal making this the warmest September in state history, surpassing that of 2015. During the month at least 173 daily maximum temperature records were tied or set within the state climate network with 14 official climate stations reporting at least one reading of 100°F or greater. In addition, 87 climate stations reported setting or tying daily warm minimum temperature records with some nights never dropping below 70°F. Yet more record-setting temperatures are expected for this Saturday, the last day of the month. September temperature extremes in the state ranged from 104°F at Theilman (Wabasha County) on the 5th to 27°F at Hibbing on the 13th.

Rainfall was extremely variable across the state. Some areas received less than an inch of rain for the month, especially in southwestern counties. In the northeast counties many climate observers reported over twice normal rainfall, exceeding 6 inches in many places. And yet more rainfall is expected for the last day of the month on Saturday. Some long-term climate stations have already set records for their wettest ever September, including:

Duluth 10.06 inches
Two Harbors 7NW 9.24 inches
Wolf Ridge ELC (Lake County) 7.62 inches
Tettegouche State Park 6.99 inches

Dozens of daily rainfall records were set during the month, mostly in northeastern Minnesota, and the statewide average rainfall for the month of nearly 3.5 inches is above normal, marking the first month with a statewide average precipitation above normal since last April.

According to the U.S. Drought Monitor the rains of last week helped to reduce the area of Minnesota affected by Moderate Drought or worse. This area shrunk by over 17 percent. However over 80 percent of the Minnesota landscape remains in the grip of Moderate Drought or worse as we end of the month of September.

Corn and soybean harvesting was just starting to ramp up earlier this week when the rains came. Some observers have reported 5-7 days of rain over the last week. This has slowed harvest activity significantly as farmers wait for the crop and the soils to dry out more before resuming harvest. In many areas of the state the rains brought sighs of relief as they helped replenish soil moisture, which was very low for the past month or more.

Old Quote About October:

For many Minnesotans, October is a favorite month. It is worth repeating what the Minneapolis Journal said about October in 1895

"October is generally a kingly month in Minnesota. It opens with the usual affluence of sunshine and quickening, bracing air which stimulates ......summer's silent fingering will be overwoven with pageantry of color which no human art can call into being. The recessional of the year is grander than the processional."

Weekly Weather Potpourri:

The United Kingdom Met Office released a new global data set on temperature and humidity. The data clearly are related to the extreme episodes of heat that in recent years documented to have immense impact on human health. Scientists who have examined this new data set have “uncovered new ways of examining different types of heat event, for example ‘hot and dry’, ‘hot and humid’ or ‘warm and humid’. Each of these types of extreme heat have different characteristics and require different cooling methods to combat the effects of the type of heat. The new dataset allows users assess what sort of heat event different regions or seasons are mostly experiencing which will help with adaptation measures to cope with our changing climate.”

There is an interesting article by Jonathan Erdman of the Weather Underground web site that shows graphically how smoke from the Canadian wildfires crossed the Atlantic Ocean this season causing smoky skies over Ireland. Fires have burned roughly 69,000 square miles in Canada so far this year.

In this week’s AGU-EOS Bulletin is an article about researchers who have used a new technique to exam the frequency and magnitude of historical tropical storms. They reported that lead-210, a naturally occurring radioactive isotope, could be used as a chemical marker of old storms buried in the geological record. Testing this method has been successful already in some areas to better document a longer history of tropical storm activity.

MPR listener question:

October is our last full month on Daylight Savings Time, as we go back an hour on the first weekend of November. How many minutes of daylength do we lose during the month of October?

Answer:

In the Twin Cities area, we lose about 70 minutes of daylength during the month of October. This compounds the effect of going off Daylight Savings Time on the first weekend of November when we set our clocks back one hour and it suddenly gets dark at 5:00 pm.

Twin Cities Almanac for September 29th:

The average MSP high temperature for this date is 67 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 48 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 29th:

MSP records for this date: highest daily maximum temperature of 89 degrees F in 1897; lowest daily maximum temperature of 44 degrees F in 1985; lowest daily minimum temperature of 27 degrees F in 1945; highest daily minimum temperature of 64 degrees F in 1877; record precipitation of 2.68 inches in 1881. No snow has fallen on this date.

Average dew point for September 29th is 45°F; the maximum dew point on this date is 68°F in 1983; and the minimum dew point on this date is 23 degrees F in 1993.

All-time state records for September 29th:

The state record high temperature for this date is 96 degrees F at Moorhead (Clay County) in 1897. The state record low temperature for this date is 13 degrees F at Hallock (Kittson County) in 1899. The state record precipitation for this date is 3.45 inches at New Ulm (Brown County) in 1925. The state snowfall record is 2.1 inches at Pokegama Dam (Itasca County) in 1899.

Past Weather:

The warmest September 29th in state history occurred in 1897 when most climate stations reported afternoon high temperatures of 80°F or higher. Temperatures of 90°F to 96°F were reported from 17 Minnesota counties.

The coldest September 29th was in 1899 when most places in the state reported frost. In northern Minnesota fourteen counties reported morning low temperatures in the teens F, while the afternoon high temperature a Park Rapids barely climbed above freezing at 33°F. Snowfalls were reported from four northern climate stations as well.

A slow-moving low pressure system brought heavy rains to many parts of western and northern Minnesota over September 20-30 of 1995. Many climate observers reported 2 inches to 4 inches of rainfall, and a few exceeded 5 inches. These heavy rains delayed crop harvests for up to 10 days.

Outlook:

Warming trend over the weekend with chances for showers and thunderstorms. Continued warm temperatures for Monday and Tuesday next week, with increasing chances for showers by Tuesday. Cooler for the balance of next week with chances for showers each day Tuesday through Thursday.