Wetness Continues in July

Wetness Continues in July:

Many climate observers have reported heavy rains again this month, especially in west-central and southeastern Minnesota. Areas in Wabasha and Winona Counties have reported over 6 inches of rain so far this month, and in the west Montevideo and Alexandria have reported over 5.5 inches of rain so far. Within the statewide climate station network there have been at least 28 new daily record rainfalls set so far this month.

In this context, I thought it would be good to compare some year-to-date precipitation amounts with our climate history.

The wettest year-to-date statewide average precipitation (Jan 1-Jul 23) was in 1993 with a value of 21.20 inches. Here are the top 5 historically:

1993 21.20”
1897 20.61”
1999 20.48”
1953 20.46”
2014 20.31”

The value for the statewide average precipitation in 2024 so far is a new record 21.22 inches. This is a remarkable high number considering that we started the year with January and February delivering below normal precipitation averages across the state, and March bringing only near normal values of total precipitation. It is the abundant precipitation of April, May, June, and July so far that has produced this record clip of wetness. Over 35 DNR-State Climatology Office observers have reported over 30 inches of precipitation this year. At this level, it is a given that many climate stations in the state will likely end up with over 50 inches of precipitation for the year 2024, a number that is equivalent to the average annual amount in Athens, GA. Some heavy rains across the state during the remainder of the year could push some locations toward the statewide annual precipitation record of 60.21 inches at Harmony (Fillmore County) in 2018.

A few striking examples of surplus precipitation from the state climate network may help illustrate this point:

Wells (Faribault County) 36.96” of year-to-date precipitation, normal annual is 34.51”
Faribault (Rice County) 34.68” of year-to-date precipitation, normal annual is 35.45”
Mankato (Blue Earth County) 32.51” of year-to-date-precipitation, normal annual is 36.40”

These large amounts of precipitation are due to both heavy individual daily rainfalls, but also the frequency of days that have brought rain, which is up to 20 percent more than the historical average frequency.

It will be interesting to see what the rest of the year brings.

Weekly Weather Potpourri:

There is an interesting article posted this week on the Weather Underground web site that documents the maximum 24-hr rainfall recorded in each state historically. It is noteworthy to see that both Texas and Hawaii have reported record-daily rainfall values over 40 inches. Among the states around the Great Likes the highest recorded daily rainfall values are 16.9 inches in Illinois and 15.1 inches in Minnesota. In the drier western states the values are lower, with a maximum daily value of just 5.1 inches in Utah.

The BBC Weather Center reports this week on analysis by the U.K. Met Office that shows the frequency of “hot days” (above 86°F) is increasing across most of the country. In addition the frequency of heavy rainfall is also on the increase for many areas, with a number of record-setting rainfalls in recent years.

A new study in the journal Science Advances documents the importance of Saharan Dust in the rainfall produced by hurricanes over the Atlantic and Gulf States in the southeastern USA. Depending on the density of the dust plumes as they migrate across the Atlantic Ocean, they may have the effect of either enhancing rainfall from tropical storms, or in some cases suppressing the formation of tropical storms. The authors suggest that further study of the detailed effects of these dust plumes may help hurricane forecasting.

MPR listener question:

With all the surplus rainfall and flooding this year, we were wondering if there is any place in Minnesota that is recording below normal precipitation for 2024?

Answer:

I checked the climate network reports carefully making sure there were not missing data and the driest areas of the state this year on in parts of the Red River Valley and north-central counties. But most of these are still close to normal precipitation for the year, or even a little bit wetter than normal. For example, Ada in the Red River Valley (Norman County) reports 15.35 inches of precipitation so far in 2024 and their normal amount by this time is 15.29 inches. In contrast, many climate stations are reporting total precipitation so far that is 5 to 10 inches above normal, and some are in the range of 12 to 15 inches above normal.

Twin Cities Almanac for July 26th:

The average MSP high temperature for this date is 83 degrees F (plus or minus 7 degrees F standard deviation), while the average low is 65 degrees F (plus or minus 6 degrees F standard deviation).

MSP Local Records for July 26th:

MSP records for this date: highest daily maximum temperature of 100 degrees F in 1955; lowest daily maximum temperature of 68 degrees F in 1972; lowest daily minimum temperature of 45 degrees F in 1962; highest daily minimum temperature of 76 degrees F in 1931, and record precipitation of 2.44 inches in 1990. No snowfall has occurred on this date.

Average dew point for July 26th is 60°F; the maximum dew point on this date is 77°F in 2003; and the minimum dew point on this date is 37 degrees F in 1974.

All-time state records for July 26th:

The state record high temperature for this date is 107 degrees F at Beardsley (Big Stone County) in 1931. The state record low temperature for this date is 27 degrees F at Tower (St Louis County) in 1980 and at Kelliher (Beltrami County) in 2001. The state record precipitation for this date is 6.52 inches at St Peter (Nicollet County) in 2020. There has been no snowfall on this date.

Past Weather:

By far the warmest July 26 in state history was in 1931 when 32 Minnesota counties reported an afternoon temperature of 100°F or greater. In western Minnesota, the overnight low temperature in Wheaton and Alexandria never fell below 80°F.

Heavy thunderstorms brought 2 to 4 inches of rain to southwestern Minnesota on July 26 of 1968. Many farm fields were flooded and drainage ditches were running a capacity.

July 26 in 1080 brought frosts to portions of north-central and northeastern Minnesota. The temperature fell to just 27°F at Tower in St Louis County.

Outlook:

Warm and humid over the weekend with a chance for showers and thunderstorms in northern Minnesota, but mostly dry in the south. Increasing clouds on Sunday with a chance for showers or thunderstorms by evening in most areas, perhaps carrying over into Monday in southern counties. All of next week will bring warmer than normal temperatures with chances for widely scattered thunderstorms.