Heat and High Dew Points Bring Welcome Widespread Rain:
June 9th and 10th this week brought very warm temperatures (over 20 climate stations reported daily highs of 90s°F or greater), along with the highest dew points of the month so far. Many climate stations reported dew points in the low to mid 70s F, and in some cases this produced afternoon Heat Index Values close to 100°F.All of the first 10 days of June have brought warmer than normal temperatures to Minnesota, though very few daily temperature records have been broken. Most climate stations are reporting an average temperature so far that is from 7°F or 8°F warmer than normal. This means that the first 10 days of this June rank among the top 5 warmest in history for many locations around the state, including the Twin Cities.
The high dew points are measurements directly related to atmospheric water vapor and associated with the showers and thunderstorms that were so prevalent this week. Orwell Dam (Otter Tail County) and La Crescent (Houston County) have already reported over 4 inches of rain this month. But they are the exceptions. Many climate observers from all areas of the state have reported between 1 and 2 inches of rainfall this week, though areas designated to be in Moderate Drought (22 percent of the state landscape) and areas designated to be in Severe Drought (10 percent of the state landscape) expanded over the previous week according to the U.S. Drought Monitor.
According to NOAA Outlook models cooler than normal temperatures will prevail across the state from this Saturday through next weekend, with more frequent chances for rainfall. According to the USDA reports 78 percent of Minnesota’s corn crop is currently in good to excellent condition, and 67 percent of the soybean crop is in good to excellent condition.
Weekly Weather Potpourri:
According to the BBC Weather Center, the first part of June has brought abundant moisture to many parts of the United Kingdom where rainfall totals already exceed the monthly average for June. In fact, for many areas, June rainfall has exceeded the rainfall totals for March, April, and May combined. Spring was an exceptionally dry one for many parts of southern and eastern England.The week, the Weather Channel web site features an analysis of the risks associated with excessive heat at the Canadian, American, and Mexican venues that are hosting World Cup soccer matches over the next two months (June 11 to July 19). FIFA has imposed some special measures to keep players and fans safer from the dangers of heat, among them mandatory 3-minute cooling breaks in each half, and later evening starting times to avoid daytime sun and heat. The outdoor conditions at the venues in Miami, FL, and Monterrey, Mexico are thought to be the most challenging. American venues at Houston (TX), Atlanta (GA), and Arlington (TX) are air conditioned, so heat and humidity will not likely affect the players in those games.
MPR listener question:
Why is it that dew points seem to rise shortly after sunset in Minnesota? Often times the maximum dew points seem to occur late in the day.Answer:
In our Minnesota climate the boundary layer depth of the atmosphere where a great deal of vertical mixing takes place, grows during the day when the sun is out and heating the Earth’s surface. Thus, the size or volume of the boundary layer increases and along with its capacity to hold water vapor. When the sun goes down, there is a reduction in the vertical mixing of the atmosphere but transpiration (release of water vapor from vegetation) continues to feed moisture into the boundary layer, as the total volume of the boundary layer shrinks. This produces a net gain in atmospheric water content that may last for a few hours. Thus, the higher dew points.Twin Cities Almanac for June 12th:
The average MSP high temperature for this date is 78 degrees F (plus or minus 7 degrees F standard deviation), while the average low is.60 degrees F (plus or minus 7 degrees F standard deviation).MSP Local Records for June 12th:
MSP records for this date: highest daily maximum temperature of 95 degrees F in 1956; lowest daily maximum temperature of 51 degrees F in 1929; lowest daily minimum temperature of 39 degrees F in 1877; highest daily minimum temperature of 72 degrees F in 1920, and record precipitation of 2.35 inches in 1899. No snowfall has occurred on this date.
Average dew point for June 12th is 55°F; the maximum dew point on this date is 74°F in 1961 and the minimum dew point on this date is 30 degrees F in 1969.
All-time statewide records for June 12th:
The state record high temperature for this date is.102 degrees F at Crookston (Polk County) in 1893 and at Redwood Falls (Redwood County) in 1956. The state record low temperature for this date is 19 degrees F at Isabella (Lake County) in 2000. The statewide record for precipitation on this date is 8.00 inches at Minnesota City (Winona County) in 1899. No snow has fallen on this date.Past Weather:
Thunderstorms brought heavy rains to many parts of southern Minnesota over June 11-12 of 1899. Many observers reported from 2 to 5 inches of rain, while near Faribault and St Charles over 5 inches of rain occurred. At Minnesota City, a state record of 8 inches of rain was measured.Perhaps the warmest June 12th in state history was in 1956 when over 45 Minnesota climate stations reported record high maximum temperatures, mostly in the 90s F. Four counties in southwestern Minnesota reached 100°F or higher.
A cold morning greeted campers in northern Minnesota on June 12 of 1985. Four northern Minnesota counties reported frosts with some areas recording morning low temperatures in the 20s F. The daytime high temperature at Brainerd only reached 52°F.
Outlook:
Cooler and breezy over the weekend, with below normal temperatures and chances for showers in northern counties. This temperature pattern will prevail most of next week. There will be a chance for showers and thunderstorms by Wednesday and Thursday, with temperatures rising back closer to normal by next weekend.
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