May and Spring 2009 Saint Cloud Weather Summary
Temperatures Warm Up Early Then Fall Back Throughout the Spring
May and Spring 2009 Saint Cloud Weather Summaries
Spring 2009 (March 1-May 31) included a record-setting March, but dry conditions ended up dominating the weather conversation. The Spring 2009 total melted precipitation in St. Cloud was 7.66 inches, 1.06 inches above normal. However, more than 60% of this precipitation (4.66 inches) fell during the wettest March in St. Cloud records. From April 1 through June 7, only 3.11 inches fell, far short of the normal 6.10 inches in St. Cloud. Making conditions worse was that most of the rain in April and May fell only on a couple of days. 0.83 inch of the 1.37 inch in April fell on April 26 and 1.30 inch of the 1.63 inch in May fell on May 15.
The ground did begin to thaw during the second half of March, so some moisture before April 1 did make it into the soil in central Minnesota. Still, the Minnesota State Climatology Office growing season statistics (which begin on April 1) show a 3-5 inch rain shortfall through June 1 just to our southeast from Clearwater and Clear Lake through the Twin Cities Metro. In fact, May 2009 was the third driest May in the Twin Cities Metro. More importantly, areas to our southeast had the largest rainfall deficits from the middle of last summer through this spring are approaching 10-12 inches. For this reason, the National Drought Mitigation Center's June 2 Drought Monitor shows that the Wisconsin drought has spread into east central and southeastern Minnesota with severe drought conditions in the Twin Cities area.
The year-to-date fire map from the Minnesota DNR shows that over 9000 acres has burned during this spring. Ironically, the one factor that has reduced the impact of the drought is the very cool conditions. Moisture loss through evaporation is reduced when the temperatures are cooler, so the cooler than normal weather, especially through the second half of May, lessened the impact of the dry weather.
Still the drier than normal April and May did not reduce the impact of the wet March. Minor flooding resulted on the Sauk and Mississippi River in St. Cloud, but the worst flooding took place in the Red River Valley. There was a record high crest in Fargo-Moorhead and the Red River stayed out of its banks in Fargo for 62 consecutive days, setting a new record.
After a significantly colder than normal winter, central Minnesotans were looking forward anxiously to a mild spring. Instead, Saint Cloud had a near normal spring which ended up feeling much colder than normal. The average temperature from March 1 through May 31 at the Saint Cloud Regional Airport was 42.3°F, 0.8°F cooler than normal.
One trend that made it feel colder is that, every time we hit a high temperature threshold, we ended up cooling off for a while. Our first high of over 60 degrees (April 14) and over 70 degrees (April 17) occurred during a mild period in mid-April. That first 60-degree high was nearly right on time, but the first 70-degree high was nearly two weeks early. However, after the end of that warm spell, the high temperature only broke 70 on one day between April 18 and May 6. On that one warm day, the high hit 85 on April 23, also 15 days earlier than normal, but the next high of at least 80 didn't happen until May 18.
The worst example of this early warmth followed by cold was our first 90-degree high on May 20. On that day, St. Cloud set records in all three temperature categories. In the 19 days since May 20, St. Cloud's temperature has been colder than normal 17 times. We've had only 2 days with a high of 80 or higher, both in May, but 7 days when the high didn't break 70. Fourof those chilly highs didn't crack 60 degrees including both days this weekend and likely today as well. From May 21 through June 7, the St. Cloud average temperature has been 55.8°F (high of 69.4°F, low of 42.2°F). The normal St. Cloud average temperature for these 18 days is 60.9°F (high of 73.4°F, low of 48.4°F). The first week of June has been even worse, averaging 8.6°F colder than normal.
That late May cold streak ended up producing an average May temperature of 55.3°F, 1.2°F degrees colder than normal.
Also, May 2009 marks the fourth consecutive month of cooler than normal temperatures with February and March being the most below normal. Because of this, many of the weather-related "signs of spring" were delayed. Lake ice melted about 10 days to 2 weeks later than normal, with Mille Lacs Lake only becoming ice-free on May 4, within 3 days of its latest ice out date. Saint Cloud didn't experience its first (and only one to date) 80-degree high until May 16, which is 12 days later than normal. Ironically, the temperature never got cooler than 33°F at the St. Cloud Airport, so our last day of frost was April 29. That would be only 5 days later than the earliest ever. Ironically, just to our north, there have been frosts and freezes as recently as last Wednesday. Since there has never been a frost later than June 1 in St. Cloud, I would guess that we are now safe.
The cool May conditions were produced by a weather pattern of slow-moving storms that either passed just to the south of Minnesota or moved over us. This kept Saint Cloud either in the clouds or in the cooler air masses being pulled southward by these storms as they passed to our east. This was similar to the late March-April weather pattern, except that, in April, the northern fringe of these storms was cold enough to dump wet snow or mixed precipitation over much of Minnesota.
The storm track did creep further to the north during the past week, allowing Minnesota to get into the warm sector during some of these storms. That wasn't good news, because there has been a lot of severe weather in the warm air during this spring, including a five-month tornado total that has equalled the 10-year average number of tornadoes for the entire year. In Minnesota, the warm sector produced four tornadoes on Sunday, May 25 from the northern suburbs of the Twin Cities into western Wisconsin, including the Hugo tornado that killed one person and damaged over 300 homes. The storm produced damage of EF3 on the enhanced Fujita scale, meaning that it was consistent with winds in the 136-165 MPH range. However, on the same day, a stronger tornado flattened Parkerburg in northeastern Iowa, killing 6 people and injuring 70. That storm did damage that was consistent with winds over 200 MPH and was rated EF5. In Saint Cloud, there was some large hail (1-2 inch diameter) with earlier storms around noon.
The severe weather potential has been enhanced by the persistent cool weather over the Northern Tier of the US. The jet stream, the current of strongest winds in the lowest 10 miles of the atmosphere, is fueled by the temperature difference between the cool air to the north of the jet and the warm air to the south. You can see this on the linked jet stream image from weatherquestions.com. Since we have remained very cool, that temperature difference has been much greater than in most recent years. In fact, several recent years have had less than normal tornado activity, especially in Minnesota where we have had severe dry periods for large parts of recent late springs and summers.
The wet weather pattern that began the second half of March continued into May. While St. Cloud did have clear sky on 20 of the 31 days, the strong storms did dump 3.83 inches of rain at the Saint Cloud Airport, 0.86 inch above the normal amount of 2.97 inches. This included two days with over an inch of rain, including a record 1.37 inches that fell on May 29. For the spring (March 1-May 31), the Saint Cloud Regional Airport picked up 8.24 inches, more than an inch and a half of above the normal amount of 6.60 inches. The big news of the first half of the spring was that the precipitation was cold enough to produce 28.7 inches of snow, more than double the normal spring snowfall. In fact, 2008 ended up being the 5th snowiest spring in St. Cloud records. The spring snowfall accounted for 55% of the total seasonal snowfall (52.2 inches), only the 8th year in St. Cloud records when the spring contributed that much of the total year snowfall.
The persistent rainfall has made a huge difference in statewide water supplies. Streamflow, according to last week's DNR report, is back to normal through most of central Minnesota. Lake Superior levels, which were hovering near record low levels last fall, are still 8 inches below normal through April, but have climbed 10 inches in the past year. According to the US Drought Monitor, only a small portion of northwestern Minnesota is listed within any drought category. The wet conditions continue to hamper crop planting as growth statistics continue to be well behind the 5-year averages, according to this week's Minnesota Ag News from the USDA. Keep in mind, however, that recent springs have been abnormally warm and dry, so the 5-year average conditions are not normal over the long term.
So, we have now been cooler than normal for four straight months, but not extraordinarily cold in any given month. None of the months ranked among the 10 coldest in St. Cloud records. Only 4 daily record cold temperatures were set, two in February and two in April. That doesn't mean we had extreme cold; it means that recent winters and springs have been very warm. Since 1980, there have been only 4 Mays that have been at least as cool as this May, the most recent being 2002. I've been using the comparison to 2001-2002 a lot, but note that 2002 was the 4th coldest spring in St. Cloud records, so it was much cooler than year. On the other hand, 5 of the last 11 springs, including 2006 (6th warmest) and 2007 (8th warmest), have ranked among the 25 mildest springs. So, we have become used to the mild springs, rather than normal or cooler than normal springs. So, any comparison to the past 10 years at this time is flawed because our recent springs have been so mild.
It does look like the weather pattern for the next week will be similar to the wet weather pattern we've seen over the past two weeks, meaning that we will have a good chance of showers and thunderstorms through much of the upcoming week. We could pop out with a really warm day, but clouds could mess that up.
Average High Temperature (°F) Average Low Temperature (°F) Mean Temperature for May (°F) May 2009 Days with High Temperatures =>90°F May 2009 Days with High Temperatures <= 32°F May 2009 Days with Low Temperatures <= 32°F Cold-season 2008-2009 Days with Low Temperatures <= 32°F
May 2009 Days with Low Temperatures >= 70°F
Spring First/Last High Temperatures Warmest High Temperature for May 2009 (°F) Coldest High Temperature for May 2009 (°F) Warmest Low Temperature for May 2009 (°F) Coldest Low Temperature for May 2009 (°F) May 2009 Days with Measurable (>= 0.01 inch) Precipitation May 2009 Days with >= 0.10 inch Precipitation May 2009 Days with >= 0.25 inch Precipitation May 2009 Days with >= 0.50 inch Precipitation May 2009 Days with >= 1.00 inch Precipitation
Average High Temperature (°F) Average Low Temperature (°F) Mean Temperature for Spring (°F) Spring 2009
Days with High Temperatures => 90°FSpring 2009
Days with High Temperatures <= 32°FSpring 2009
Days with High Temperatures <= 0°FSpring 2009
Days with High Temperatures <= -10°FSpring 2009
Days with Low Temperatures >= 70°FSpring 2009
Days with Low Temperatures <= 32°FSpring 2009
Days with Low Temperatures <= 0°FSpring 2009
Days with Low Temperatures <= -20°FSpring 2009
Days with Low Temperatures <= -30°FSpring 2009 Days with Measurable (>= 0.01 inch) Precipitation Spring 2009 Days with >= 0.10 inch Precipitation Spring 2009 Days with >= 0.25 inch Precipitation Spring 2009 Days with >= 0.50 inch Precipitation Spring 2009 Days with >= 1.00 inch Precipitation
Send comments to: raweisman@stcloudstate.edu