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Comments on last spring frost

Last Spring Frost?

The agricultural planting season has progressed well with a majority (close to 75 percent) of the corn crop planted and more than a third of the soybean acreage planted. In addition gardeners are removing mulches, planting potted plants outdoors and putting in garden vegetable seeds. Some have even mowed their lawns already. Many have been asking if the last spring frost is behind us.

For the Twin Cities Metro Area the last sub-freezing temperature reported at the MSP Airport was on April 12th with 27°F, but surrounding communities like Stillwater (26°F), New Hope (32°F), and Chanhassen (32°F) reported frost on April 29th.

For most other places in the state I think the last spring frost has already occurred as well. For southern Minnesota communities the last sub-freezing temperatures were on April 13th including:
30°F at Marshall
28°F at Albert Lea
27°F at Zumbrota
In western and central Minnesota counties the last sub-freezing temperatures were during the last week of April, including:
32°F at Canby and Milan on the 29th
31°F at Collegeville and St Cloud on the 29th
30°F at Moose Lake on the 29th
In northwestern Minnesota counties of the Red River Valley, sub-freezing temperatures occurred a recently as May 1st, including:
24°F at Thief River Falls
31°F at Detroit Lakes and Roseau
32°F at Moorhead

Given the forecasts for the balance of May, there will be some nights with cooler than normal temperatures, but it is likely that the communities listed above have already seen their last frost of the spring occur.

Of course areas of north-central (Bemidji, International Falls) and northeastern Minnesota (Tower and Embarrass) may very well continue to have frosts in late May and early June, because the gardening season always starts later in those area.

Warm Temperatures:

This spring so far, March 1st to May 6th has brought warmer than normal temperatures (roughly 4°F above average) and wetter than normal conditions to most areas of the state. The March-April two-month period in 2016 ranks among the ten warmest such periods in state history back to 1895.

Prior to Thursday, May 5th the only period that brought 80 degrees F temperatures to the state was over April 14-17 last month, when over 60 Minnesota communities reported afternoon highs of 80°F or higher, topped by 86°F at Wheaton (Traverse County). These values were topped in western and northwestern Minnesota on Thursday, May 5th this week, with many areas reporting 90°F or warmer. Roseau and Hallock topped the list with 93°F. That was a new daily high temperature record for Roseau. Warroad also set a new record daily high with 91°F on the 5th, as did Thorhult with a reading of 90°F, while Fosston tied the daily record with a reading of 90°F.

Weekly Weather Potpourri:

My wife Cindy and daughter Emma are taking me this week to hear Paul McCartney at Target Center (a birthday present). Like most people I have my favorite Beatles songs, many of which relate to the weather. In fact last year a science writer posted a piece in the UK's Daily Telegraph where she hypothesized that the Beatles popularity in was at least in part enhanced by their singing about the weather which most Brits relate to. 48 of their songs relate to the weather and George Harrison wrote "Here Comes the Sun" after the cold, cloudy winter of 1969.

A large wildfire around Fort McMurray in Alberta, Canada was burning out of control this week. It has burned over 200,000 acres and destroyed over 1600 structures, as well as causing the evacuation of over 90,000 people. Persistent warm (temperatures in the 70s and 80s F) and dry climate conditions across Alberta had set up the suitable conditions for this fire to occur. Sunny and dry conditions are expected to prevail until Sunday (May 8th) when some welcome showers are forecast to reach this area of Alberta. Through their Earth Observatory web site NASA posted several images of the fire.

Environment Canada was releasing air quality alerts for portions of eastern Alberta and western Saskatchewan because of the intense smoke from the fire.

Other news this week out of Canada is that climate change, notably warmer temperatures have provoked more algal growth in the Athabasca oil sands of northern Alberta. Scientists from Queen's University studied climate and lake sediments from 23 remote lakes far removed from industrial pollution. They believe the increased algal production in these lakes is driven by aerial nutrient fertilization (atmospheric deposition) enhanced by a warmer temperature pattern. You can read more at the Science Daily web site.

EOS, published by the American Geophysical Union features an article about the Coupled Model Intercomparison Project (CMIP) used as a tool to improve and validate climate models against measured climate data sets. A great deal of work is being done to improve the current generation of climate models, now number twenty in total.

Millions of people in India were relieved to see some significant Pre-Monsoon rains occur across their country this week bringing relief from a Heat Wave that had started in late April and the first two days of May. Temperatures had soared well above 100F during the Heat Wave and caused widespread suffering and even loss of life. In Orissa the thermometer had measured a temperature of 119F the highest reading ever in the month of April. The rains this week were also welcome from the standpoint of drought relief in some parts of the country. You can read more at the CNN News web site.

The U.S. Climate Resilience Toolkit from NOAA announced this week a new Climate Change Atlas that shows current and projected geographic distribution of 134 tree species and 147 bird species across the Eastern USA. The atlas can be used to assess future suitable habit for a range of species.

MPR listener question:

I noticed in the afternoon weather round-up on Thursday, May 5th at 3pm that many northwestern Minnesota communities were reporting 90 degrees F or greater, including Hallock, Moorhead, Roseau, Fosston, Warroad, Thief River Falls, Thorhult, and Crookston. Yet across to the east about 300 miles at Grand Marais, the temperature was 41°F. How often does this range in temperature occur in Minnesota?


More often than you think, especially this time of year. When the Minnesota landscape is warming up in the spring, but not yet covered by farm crops the soils can warm dramatically, especially in western counties. Conversely the temperatures of the areas around Lake Superior are still modified significantly by Lake Superior, which is slow to warm after the cold winter conditions. As a result temperature differences of 50 degrees F or greater can be observed across Minnesota at the same moment in time during the months of April and May. On May 19, 2009 at 4:00 pm the temperature was 100°F at Milan (Chippewa County), but just 35°F at Grand Marais Harbor (Cook County). I might further add that this often happens under conditions of very low relative humidity and bright sunshine. Relative humidity values on Thursday, May 5th ranged from just 8 to 19 percent in northwestern Minnesota, but were closer to 80 percent at Grand Marais.

Twin Cities Almanac for May 6th:

The average MSP high temperature for this date is 67 degrees F (plus or minus 12 degrees F standard deviation), while the average low is 46 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for May 6th:

MSP weather records for this date include: highest daily maximum temperature of 89 degrees F in 1896 and again in 1934; lowest daily maximum temperature of 35 degrees F in 1931: lowest daily minimum temperature is 25 degrees F in 1989; highest daily minimum temperature of 67 degrees F in 1896; record precipitation of 1.51 inches in 1939; and record snowfall of 6.6 inches in 1984.

Average dew point for May 6th is 37 degrees F, with a maximum of 66 degrees F in 1965 and a minimum of 14 degrees F in 1989.

All-Time State Records for May 6th:

The state record high temperature for this date is 98 degrees F at Grand Meadow (Mower County) in 1934. The state record low temperature for this date is 12 degrees F at Alborn (St Louis County) in 1944. State record precipitation for this date is 3.78 inches at Lake Wilson (Murray County) in 2012; and record snowfall is 10.0 inches at Roseau (Roseau County) in 1938.

Past Weather Features:

May 6, 1934 was the hottest in state history, with 20 climate stations reporting daytime temperatures of 90F or higher. It was a precursor to one of the hottest months of May in state history. Hundreds of daily maximum temperature records were set that May.

In both 1925 and 1944 low temperatures fell into the teens and twenties F on May 6th. A hard freeze affected even the southern counties and damaged emerged crops. Potatoes and corn crops had to be replanted in some areas.

A rare winter snow storm crossed the state over May 5-6, 1938 dropping several inches of snowfall. Northern counties measured 3 to 10 inches. The snow was short-lived as temperatures warmed from the 30s F into the 60s F by May 8th.

Persistent heavy rains delayed farm field work during the first week of May in 1964. Many areas of the state received 2-3 inches of rainfall. Planting was delayed over a week to allow fields to dry out.

May 6, 1965 brought a deadly tornado outbreak to the Twin Cities Metro Area. Six tornadoes occurred during the evening hours injuring nearly 700 people and killing 14. It was the second consecutive day of tornadoes in the state. The Minnesota State Climatology Office provides a good retrospective on this significant weather event.


Generally a sunny weekend with near seasonal temperatures. Increasing cloudiness on Monday with a chance for showers and thunderstorms. A more active weather pattern will dominate next week with cooler temperatures, persistent cloudiness and a chance for showers each day.
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