Cool May Marks 4th Straight Below Normal Month
May and Spring 2008 Saint Cloud Weather Summaries
For the fourth consecutive month, Saint Cloud's average temperature was cooler than normal. However, temperatures were not even close to record cold levels. The May average temperature at the Saint Cloud Regional Airport was 53.4°F, 3.1°F cooler than normal. That ties 1882 and 1935 as the 26th coolest May out of the 127 Mays on record. And, this May could have been colder if not for near normal weather during the last 9 days of the month. Through May 22, the average May temperature was 51.5°F, close to one of the ten coldest Mays on record. Temperatures had been colder than normal on 17 of the first 22 days. High temperatures had been cooler than 60°F on 6 of the first 22 days, including a high of 43 on May 2. While we didn't have any heat waves late in May, temperatures were much closer to normal, adding nearly two degrees to the average temperature.
The spring (March 1-May 31) average Saint Cloud temperature was also cooler than normal. The average temperature was 39.7°F, 6.4°F cooler than normal, but that only ranks as the 27th coolest spring in Saint Cloud records that go back to 1881.
Also, May 2008 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 2008 Days with High Temperatures =>90°F May 2008 Days with High Temperatures <= 32°F May 2008 Days with Low Temperatures <= 32°F Cold-season 2007-2008 Days with Low Temperatures <= 32°F
May 2008 Days with Low Temperatures >= 70°F
Spring First/Last High Temperatures Warmest High Temperature for May 2008 (°F) Coldest High Temperature for May 2008 (°F) Warmest Low Temperature for May 2008 (°F) Coldest Low Temperature for May 2008 (°F) Record Daily Rainfall May 2008 Days with Measurable (>= 0.01 inch) Precipitation May 2008 Days with >= 0.10 inch Precipitation May 2008 Days with >= 0.25 inch Precipitation May 2008 Days with >= 0.50 inch Precipitation May 2008 Days with >= 1.00 inch Precipitation
Average High Temperature (°F) Average Low Temperature (°F) Mean Temperature for Spring (°F) Spring 2008
Days with High Temperatures => 90°FSpring 2008
Days with High Temperatures <= 32°FSpring 2008
Days with High Temperatures <= 0°FSpring 2008
Days with High Temperatures <= -10°FSpring 2008
Days with Low Temperatures >= 70°FSpring 2008
Days with Low Temperatures <= 32°FSpring 2008
Days with Low Temperatures <= 0°FSpring 2008
Days with Low Temperatures <= -20°FSpring 2008
Days with Low Temperatures <= -30°FSpring 2008 Days with Measurable (>= 0.01 inch) Precipitation Spring 2008 Days with >= 0.10 inch Precipitation Spring 2008 Days with >= 0.25 inch Precipitation Spring 2008 Days with >= 0.50 inch Precipitation Spring 2008 Days with >= 1.00 inch Precipitation
