Warm Start to July

Warm Start to July:

Through the first 10 days of July, temperatures are averaging 2°F to 4°F warmer than normal. Though very few record high temperatures have been reported this month, observers in over 40 counties have reported daytime highs in the 90s, and a number of observers reported Head Index Value of 100°F over July 4th and July 5th.

Except for parts of north-central and south-central Minnesota which had strong thunderstorm over July 4th and 5th, most areas of the state are reporting below normal rainfall so far. Wells (Faribault County) reported a record daily rainfall of 2,82 inches on July 5th, while Waskish (Beltrami County) reported a record rainfall of 2.67 inches on the same date.

The U.S. Drought Monitor this week shows only portions of Kittson, Roseau, Lake of the Woods, and Marshall Counties (far northwestern MN) to be in Moderate or Severe Drought. According to USDA reports topsoil moisture in the state is mostly rated to be adequate at this time and surplus in 23 percent of the landscape.

Currently NOAA outlook models favor a period of cooler than normal and wetter than normal conditions for mid-July, and then a return of above normal temperatures towards the end of the month. 

Evolution of Forecast Terminology:

When the federal government weather service was first created by Congress in 1870, they called their thrice daily predictions "probabilities." Later in 1876, they referred to their predictions as "indications." Then by 1889, they used the term "forecasts." This terminology remained in place for nearly a century until recent years when the weather service started emphasizing "probabilistic forecasts" that are based on purely numerical computer output. In simple terms, today's forecast is the most probable outcome from a set of derived numbers that represent a distribution of probable outcomes based on measurements, forecast models, and climatology.

Weekly Weather Potpourri:

In news from the AGU-EOS Bulletin, there is a new science news tracker available to keep up with policies and funding for science-based programs. It is a valuable source of information to examine the proposed implementation of policies of the Trump Administration that affect the various science-based agencies and associated services, including NOAA and NASA.

Jonathan Erdman of the Weather Underground reported that on July 8 of 2023, the dew point in Dhahran, Saudi Arabia hit 95°F. This is believed to be a world record high dew point. Combined with the afternoon temperature of 108°F that day, the Heat Index hit 178°F. Sometimes the mid-summer water temperatures in the Persian Gulf hit 90°F or higher and help to fuel the water vapor content over Saudi Arabia.

The BBC featured a story this week contrasting the two back-to-back flash flood tragedies in the USA this week, occurring first in the hill country of Texas, and then later in southeastern New Mexico. Local communities were highly impacted by these floods, but had prepared for them differently based on their climate history. 

MPR listener question:

The high dew points certainly made the 4th of July uncomfortable for us. We have listened to your chats with Cathy Wurzer for many years and heard you talk about dew points measuring as high as 80°F in Minnesota during July. Exactly how many years has this happened? 

Answer:

The first measurement of a dew point that high in the Twin Cities was on July 11 of 1966. Since that time, the Twin Cities climate record shows a dew point of 80°F or higher during July in seven other years. This list below also shows the associated Extreme Heat Index Value:

1966 1 date 114°F Heat Index
1983 1 date 109°F Heat Index
1995 2 dates 115°F Heat Index
1999 2 dates 115°F Heat Index
2002 1 date 105°F Heat Index
2005 1 date 101°F Heat Index
2011 3 dates 119°F Heat Index
2019 1 date 116°F Heat Index

In our lifetime, most of the Heat Advisories and Excessive Heat Warnings issued by the National Weather Service are due to high Heat Index Values caused by high dew point conditions. 

Twin Cities Almanac for July 11th:

The average MSP high temperature for this date is 84 degrees F (plus or minus 8 degrees F standard deviation), while the average low is 66 degrees F (plus or minus 6 degrees F standard deviation).

MSP Local Records for July 11th:

MSP records for this date: highest daily maximum temperature of 106 degrees F in 1936; lowest daily maximum temperature of 66 degrees F in 1941; lowest daily minimum temperature of 49 degrees F in 1945; highest daily minimum temperature of 82 degrees F in 1936; and record precipitation of 3.75 inches in 1909. There has not been any snowfall on this date.

Average dew point for July 11th is 60°F; the maximum dew point on this date is 80°F in 1966 and the minimum dew point on this date is 35 degrees F in 2009. 

All-time state records for July 11th:

The state record high temperature for this date is 111 degrees F at Ada (Norman County) and Campbell (Wilkin County) in 1936. The state record low temperature for this date is 30 degrees F at Meadowlands (St Louis County) in 1985. The state record precipitation for this date is 7.47 inches at Rochester (Olmsted County) in 1981. No snowfall has occurred on this date. 

Past Weather:

Far and away, the warmest July 11th in state history was in 1936. Almost all areas of the state recorded afternoon temperatures of 100°F or greater. It was as hot as 104°F at Sawbill Camp in Cook County by the Canadian border. Only a few coastal communities along Lake Superior did not see 100°F temperatures. The overnight low in Winona was 83°F.

Strong thunderstorms brought heavy rains and flash flooding to parts of southeastern Minnesota on July 11 of 1981. Many areas received 3 to 5 inches of rainfall. Hokah, Rochester, and Lanesboro reported over 7 inches of rain and many roads around those communities were flooded and closed. Flooding was reported on the Zumbro, Whitewater, and Root River watersheds.

A cold July morning greeted campers in northern Minnesota on July 11 of 1985. Temperatures were in the 30s F, and there was frost reported in parts of St Louis County. The daily high temperature at Itasca State Park only reached 68°F. 

Outlook:

Sunny and cooler over the weekend, with temperatures a bit cooler than normal on Saturday. Warmer temperatures on Sunday and Tuesday with a chance for showers and thunderstorms. Then cooler by Wednesday, but still a chance for scattered showers. Cooler and drier for next Thursday and Friday.