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Rain Shortfall Intensifies in September

Second Driest September

September 2012 Saint Cloud Weather Summary

The dry period that began in early summer intensified across Minnesota during September. According to statistics at the St. Cloud Regional Airport, the September 2012 rainfall totalled only 0.24 inches, 3.02 inches below normal. This made September 2012 St. Cloud's second driest September in St. Cloud records. The only drier September was recorded in 1952 when only 0.07 inch fell. 1952 was also the last year in which no September day had at least 0.10 inch of rain.

Largest Partial Growing Season Rain Shortfall Since 1988

The very dry conditions have come since the wet spring mostly ended in May. Between June 1 and September 30, St. Cloud has only picked up 7.41 inches of rain. The average four-month rainfall is 14.73 inches. While three of the past 4 growing seasons have had some kind of dry spell during the growing season, the 7.32 inch deficit in the past 4 months is the largest deficit and the worst than any single growing season since our last major drought in 1986-1989. In fact, June-Sept 2012 has had the third lowest June-Sept rainfall in St. Cloud records. The last year the summer and early fall was drier than this year was in 1950 when only 5.30 inches fell in those four months.

So far in October, the dry conditions have worsened. There has been no measurable rainfall in St. Cloud through October 12, so the St. Cloud rainfall deficit since June 1 totals 8.44 inches. According to the weekly drought report from the Minnesota State Climatology Office, some of the largest rainfall deficits statewide are being seen in a strip of central Minnesota running from Lac qui Parle through Glenwood, Benson, Willmar, Atwater, Paynesville, Annandale, and into Elk River. Rainfall deficits since the start of June are running 7-10 inches since mid-June. Thus, all of central Minnesota is now being listed in the severe drought category by this week's US Drought Monitor. Still, the worst conditions are in northwestern Minnesota, which missed the heavy spring rainfalls, and southwestern Minnesota. These dry conditions could push the ranking of the summer-fall 2012 to near the top of the driest single seasons. In the last 19 days of the month, St. Cloud would have to pick up more than 1.65 inches of rain to avoid beating 1950 as the year with the driest June-October period.

The very dry conditions, combined with a number of windy days, led to several outbreaks of wildfires. The most damaging fire happened in Karlstad in northwestern Minnesota in early October. Many of these fires were put out by an early October snowstorm in northwestern Minnesota, but the generally dry conditions elsewhere were causing problems during any warmer and breezy day.

The heavy spring rains, however, were enough to allow a near normal harvest of corn and soybeans. The toll has been on ground water, which must be replenished before we get too far into next spring's growing season.

Daily Temperature Roller Coaster Much Like a Desert

The "desert-like" conditions led to a roller coaster of temperatures in September, often during the same day. The average September temperature at the St. Cloud Regional Airport was 59.6°F, only 1.0°F warmer than normal. However, that was made up of a 75.5°F average high temperature (5.2°F warmer than average) and a 43.6°F average low temperature (3.2°F colder than average). Nineteen of the 30 September days had at least a 30 degree difference between the high and low temperature with 4 days producing at least a 40 degree temperature difference.

The very dry conditions helped to produce those large ranges by reducing the average greenhouse effect. Water vapor is the most abundant greenhouse gas. During dry weather periods, there is less moisture in the air than average, meaning both that more sunshine gets to heat the ground during the day, leading to warmer higher temperatures, and more earth energy goes directly out to space at night, leading to colder low temperatures. While St. Cloud is not nearly as hot as Death Valley, note that the average range (difference between high and low temperature) during September in Death Valley is about 30-33 degrees, about the same as St. Cloud had averaged in September.

Hottest September High in 34 Years

The actual temperature did break 90 degrees two more times in September, running the 2012 total of 90-degree days to 17 days. That didn't quite make it to the 20 days seen in both 2006 and 2007. That included a record-tying 96 degree high on September 11. That was the latest in the year 90-degree high since 1998 (hit 90 on September 19) and the highest September temperature since 1978 (98 degrees on September 7). A second record was tied on September 29 with a high of 84 degrees.

The relatively cool nights did produce a nearly average date of first frost (September 22, right on the average date) and first hard freeze (September 27, average October 1)

On Pace for Record Warm 2012

Through the first 9 months of 2012, the average St. Cloud temperature has been 52.2°F. That's the warmest average for the first 9 months of the year. The previous high was a whole degree cooler (51.2°F) and was set in 1931. Keep in mind that St. Cloud has already had its warmest year defined by the heating season (July 2011 through June 2012).

 

    September 2012 Statistics

Temperatures (°F)
September 2012
Normal
Average High Temperature (°F)
75.5
70.3
Average Low Temperature (°F)
43.6
46.8
Mean Temperature for September (°F)
59.6
58.6
Saint Cloud's Ten Warmest/Coldest Septembers
Temperature Thresholds
Number of Days
Normal
September 2012 Days with High Temperature of At Least 90°F
2
0.99
2012 Total Days with High Temperature of At Least 90°F
17
11.58
September 2012 Days with Low Temperature of 32°F or lower
5
1.70
September Temperature Extremes
Temperature(°F)
Date
Warmest High Temperature for September 2012 (°F)
96 (tied record, see below)
Sept 11
Coldest High Temperature for September 2012 (°F)
58
September 22
Warmest Low Temperature for September 2012 (°F)
61
September 11
Coldest Low Temperature for September 2012 (°F)
27
September 27
Record Temperatures in September 2012
Temperature(°F)
Date
Old Record
Daily Record High Temperature
96 (tie)** September 11 tied record set in 1931
84 September 29 tied record set in 1933
**Hottest September Temperature since September 7, 1978      
Precipitation (in)
This Year
Normal
September 2012 Precipitation (in)
0.24**
3.46
**Second Driest September in St Cloud Records
Saint Cloud's Ten Rainiest/Driest Septembers
2012 Growing Season (April 1- September 30) Rainfall (in)
18.77 (-1.48 from average)
20.25
2012 Wet Period (April 1 - May 31) Rainfall (in)
11.36 (+5.84 from average)
5.52
2012 Dry Period (June 1- September 30)
7.41 (-7.32 from average)
14.73
2012 Total Precipitation (in) (January 1 - September 30)
21.73
23.04
Precipitation Thresholds
Number of Days
Normal
September 2012 Days with Measurable (>= 0.01 inch) Precipitation
4
8.7
September 2012 Days with >= 0.10 inch Precipitation
0
5.6
September 2012 Days with >= 0.25 inch Precipitation
0
3.5
September 2012 Days with >= 0.50 inch Precipitation
0
2.0
September 2012 Days with >= 1.00 inch Precipitation
0
0.8
September Precipitation Extremes
Precipitation (in)
Date
Most Daily Precipitation in September 2012
0.08 inch
September 17
Record Precipitation in September 2011
Precipitation (in)
Date
Old Record
No records set
 
Saint Cloud's Driest Summer/Early Fall

June-Sept

(Average Rainfall: 14.30 inches)

June-Oct

(Average Rainfall: 16.39 inches)

Rank
June-Sept Rain (inches)
Year
Rank
June-Oct Rain (inches)
Year
1 5.30 1950 1 9.06 1950
2 7.26 1922 2 9.11 1893
3 7.41 2012 3 9.17 1976
4 7.43 1893 4 9.38 1910
5 7.68 1894 5 9.41 1936
6 7.94 1996 6 9.59 1992
7 8.10 1943 7 9.63 1894
8 8.47 2000 8 9.63 1922
9 8.49 1992 9 9.86 2001
10 8.52 1931 10 10.07 2000

 

Recent Summer-Fall Dry Periods
Year
Dates
Rainfall Departure from Average (inches)
2008 June 15 - Sept 10 -4.00
2009 April 1 - Sept 30 -4.91
2011 Aug 21 - Oct 31 -4.66
2012 June 1 - Sept 30 -7.32
2012 June 1 - Oct 12 -8.44
1987 Apr 1 - Oct 31 -6.17
1988 Apr-Oct -7.11
1989 Apr 1 - Oct 31 -5.17

 



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All climate data provided courtesy of NOAA/NWS
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and Minnesota Climatology Working Group, including the Minnesota State Climatologist's Office, University of Minnesota-Saint Paul Campus.

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Send comments to: raweisman@stcloudstate.edu
Last updated: October 13, 2012
Background courtesy of aaa-backgrounds.com

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 65.5F, 7.1F 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.