Is This Summer's High Humidity Unique?

It seems like we haven't had much of a break from the high humidity across northern Ohio. It turns out that this summer SO FAR is the most humid summer on record in northern Ohio!

Here is the list (thru July 19):

1. 2025
2. 1995
3. 1949
4. 1987
5. 1999
6. 1973
7. 1943
8. 2010
9. 1989
10. 2018

The month of June started off somewhat cool and pleasant. The first two weeks of June featured several short periods of higher humidity (dew points above 60) with sharp drop-offs each time. The second half of the month saw a huge jump in humidity with a long stretch with dew points close/slightly above 70 degrees. Since the first of July, the breaks (dew points under 60) have been few and far between.

Compare this year to last year over the same time period. We had many more breaks from the high humidity.

Why has it been so consistently humid vs last year? The 500 mB reanalysis sheds some light on this. Notice the position of the highs and lows last year in the first half of summer. Ridge off the east coast did help increase the humidity from time to time. The deeper trough in the northern US suppressed the northward movement of moisture with a more dominant NE flow aloft across the Ohio Valley.

This year is different. The high pressure ridges are a bit further north as is the northern US trough. Couple this with a weaker but persistent trough over the southern plains and you have a more dominant south/southwesterly flow across the central US and Ohio Valley.

The long range outlook heading into early August is for the higher humidity (green colors) to shift into the central US and away from the southern Great Lakes.