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First significant rain of the month

First significant rain of the month

July 9th (Tuesday) brought thunderstorms to Minnesota and the first significant rainfall of the month for many. Several observers in northern, east-central, and southeastern Minnesota reported amounts ranging from 0.50 inches to over 1 inch. Some of the larger amounts included 1.11 inches at Hallock, 1.72 inches at Waskish, 1.25 inches at Montevideo, 1.07 inches at Gaylord, and 1.00 inches at Vesta. Yet more rainfall is expected over the weekend and into next week, coming at a key time for the state's rapidly growing corn and soybean crops, and newly seeded alfalfa fields.

Comparing the Twin Cities Heat Waves of 1936 and 1995

The two hottest July 12th dates in Minnesota state history occurred in 1936 and 1995. They were both associated with multi-day Heat Waves, but there was a distinctive difference in their character. In 1936, a serious drought had a grip on the state too, as the month of July brought only 0.11 inches of rainfall following a dry spring. The core period for the Heat Wave was 13 days long, from the 6th to the 19th. Daytime highs were 95 degrees F or greater each day, peaking at 108 degrees F on the 14th. On 7 consecutive nights (the 7th to the 13th) the overnight lows never dropped below 80 degrees, peaking with a low of 86 degrees F on the 13th. Without air conditioning many Twin Cities residents slept on screen porches, in city parks, or along lake shorelines. Dew points ranged from the upper 50s to mid 60s F, not high enough to inflate the Heat Index (combination of temperature and humidity). Nevertheless the persistent heat caused approximately 180 deaths in the Twin Cities (estimated by the coroners of Hennepin and Ramsey Counties), with the peak loss of life on July 13 and 14. Statewide, officials estimated 759 lives lost due to the Heat Wave, the most in Minnesota history. By the end of the month wildfires plagued the northern counties and navigation was suspended on the Mississippi River due to very low flow volume. More modest heat prevailed the rest of the month, resulting in the hottest month of July in Minnesota's history.

The Heat Wave in 1995 lasted from July 11 to 14 and was primarily the result of unusually high dewpoints (some observers reported 80 degrees F DP values) which inflated the Heat Index. Heat Index values over the four days ranged from 97 degrees F to 115 degrees F, while the daytime maximum temperatures ranged from 90 degrees F to 101 degrees F. The overnight low on the 12th never dropped below 80 degrees F. This Heat Wave did not produce high mortality in the Twin Cities, but did contribute to nearly 500 deaths in Chicago, IL. The Minnesota Heat Wave did produce high turkey loss in central Minnesota as hundreds of thousands of birds died, and some pregnant dairy cows aborted as a result of the heat stress. Thankfully after the 15th of the month air temperatures moderated in the 80s F during the day and 60s F at night for most of the balance of the month.

Weekly Weather potpourri

Last month (June, 2013) the International Journal of Climatology published an excellent and comprehensive review article title "Land cover changes and biogeophysical effects on climate." This was written by several well know climate scientists and presents a great deal of evidence for the size and magnitude of climate change brought on by land cover changes. It is a good read in helping us understand how climate change is proceeding at a different pace in different places. You can read the paper online.

The Minnesota State Climatology Office has done a mid-season compilation of 2013 severe weather. So far only 5 tornadoes have been confirmed in the state, but we have seen plenty of heavy rains, high winds and hail associated with thunderstorms. A synopsis of the season can be found at the web site.

Monday afternoon and evening (July 8th) brought heavy thunderstorms to parts of Ontario, Canada. Toronto saw record-setting rainfall amounts exceeding 4 inches in 4 hours in some areas . This caused flash flooding closing down bus and train commuter services and overflowing the capacity of the city storm sewer system. There were also several power outages in the area. Media reported many road closures and reports of basements flooding. More information is available here.

Powerful Typhoon Soulik in the Western Pacific Ocean was heading for the island nation of Taiwan as the weekend approached. Typhoon Soulik packed winds from 110-130 mph, producing wave heights of over 40 feet. It was expected to weaken and dissipate over the weekend as it made landfall in China, bringing heavy rains to coastal areas.

On Wednesday this week (July 10th) the National Park Service and the NOAA National Weather Service hosted a 100th Anniversary celebration at the Furnace Creek Visitor's Center in Death Valley, CA in honor of the planet Earth's warmest temperature ever measured, 134 degrees F on July 10, 1913. The celebration took place during the day with temperatures ranging from 112 degrees F to 117 degrees F after an overnight low of 94 degrees F. I did not hear an estimate of attendance there.  Read more here.

MPR listener question

I riding the MS TRAM from International Falls, MN to Duluth, MN next week (July 15-19). What kind of weather do you think we'll encounter?

Answer: I see this year's TRAM has stops in Orr, Chisholm, Biwabik, and Two Harbors before arriving in Duluth on Friday, July 19th. It appears the weather each day will bring near normal temperatures (upper 70s to low 80s F during the day and upper 50s to low 60s F at night), but each day will have a chance for showers and thunderstorms. So I would recommend taking some rain gear just in case.

Twin Cities Almanac for July 12th

The average MSP high temperature for this date is 84 degrees F (plus or minus 7 degrees F standard deviation), while the average low is 64 degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for July 12th

MSP weather records for this date include: highest daily maximum temperature of 106 degrees F in 1936; lowest daily maximum temperature of 67 degrees F in 1926; lowest daily minimum temperature of 48 F in 1941; highest daily minimum temperature of 83 F in 1936; and record precipitation of 2.93 inches in 1912; No snow has been recorded on this date.

Average dew point for July 12th is 61 degrees F, with a maximum of 80 degrees F in 1995 and a minimum of 39 degrees F in 1926.

All-time state records for July 12th

The state record high temperature for this date is 111 degrees F at Canby (Yellow Medicine County) in 1936. The state record low temperature for this date is 27 degrees F at Tower (St Louis County) in 1975. State record precipitation for this date is 5.45 inches at Buffalo (Wright County) in 1961; and no snow has fallen on this date. 

Past Weather Features:

Mid-July frosts though rare in Minnesota have occurred even in the vicinity of the Twin Cities. On the mornings of July 11-14, 1863 many residents in and around the Twin Cities reported damaging frost as temperatures dropped into the 30s F. Corn, potatoes, pumpkins, cucumbers, and tomatoes were all reported to be "seriously damaged' by the frosts. Later in the month wildfires caused the air to be smoke filled on many days as well. So all in all it was a rather disagreeable month.

Thunderstorms brought heavy rain, hail, and strong winds to parts of west central and south central Minnesota over July 11-12, 1972. Wind gusts were reported to range from 55 mph to 80 mph, damaging farm buildings and knocking down trees. Heaviest rainfall amounts ranged from 4 to 7 inches over an area from Fergus Falls southeast to Melrose. Many roads and ditches flooded. Farmers reported moderate crop damage from hail, and some cattle were killed by lightning strikes in Redwood County.

July 12, 1975 was one of the coldest in state history, with some ground frost reported in northeastern Minnesota where morning minimum temperatures ranged from the upper 20s to mid 30s F. A dry, cool Canadian air mass descended on the state and even kept daytime highs in the 60s F (20-25 degrees F cooler than average). The high at Babbitt was only 66 degrees F, Grand Marais was 63 degrees F, and both Tower and Two Harbors topped out at just 62 degrees F as Mother Nature's air conditioning system brought a respite from the normal July heat. Tower was back in the 90s F by the 16th.


This acronym stands for Meteorological Phenomena Identification Near the Ground, a mobile app and computer data base that is a combined effort of the NOAA-National Severe Storms Lab, University of Oklahoma, and Cooperative Institute for Mesoscale Meteorological Studies. The mPING app provides a mechanism for filing a report on severe or unusual weather that automatically enters the database with notation about place and time. Both past and real-time reports across the nation can be viewed using the web site.

This system is used to verify severe or hazardous weather reports and radar interpretations of weather. The App can be found at Itunes or Google Play. You can read about it here.


Warmer than normal temperatures across southern Minnesota into the weekend with a chance for widely scattered showers and thunderstorms. Near normal temperatures in northern areas with a better chance for showers and thunderstorms. Warm temperatures will prevail in central and southern counties well into next week with higher dewpoints producing some Heat Index values near 100 degrees F. There will be continued chances for showers and thunderstorms much of next week as well.
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