How Often Does July Feature Above Normal Temperatures? July 2020 Outlook

Here is a look at the average OVERALL temperatures for each July for Cleveland over the last 50 years. RED circles indicate years that were above normal by at least 1 degree.

Let's add BLUE circles to indicate years below normal.

How about the number of days with ABOVE NORMAL high temperatures?
Last year we had more than average.  Yet from 2013-2015 above normal high temperatures in July were way down.

Bottom line:  July isn't always consistently hot historically like many of us believe.

So what is July 2020 looking like?

The position of the ridge of high pressure in the central US will dictate how hot we get in the Ohio Valley. This animation shows the ridge expanding after July 8th.

We'll be on the eastern edge of this heat ridge. This will more than likely allow some NW to SE moving storms to develop early next week and again mid-month...

Analog composites show this too. Something to watch.

Bottom line July Outlook:

Temperatures: Above normal (25 of the 31 days above normal)
Rainfall: Well below normal

What Is Driving This Cool Pattern? 2014 vs 2009

This unseasonably cool pattern across the Great Lakes and upper mid-west hasn't been completely unexpected. Back in April and early May, we talked about how this summer would feature periods where temperatures would drop below normal. Take a look at the 12 day stretch from July 15th to July 26th. The area of the US that experienced below normal temperatures this year is exactly the same as 2009.

2009 was one of our years we used as a guide in formulating our summer outlook. Remember, this does not include this week's cool-down. I'll redraw this anomaly map at the end of this week.

The upper level (18,000 foot) trough is a bit stronger this year but in the same location as 2009.

Notice where the ridge (high pressure) is located: The western US where the present drought is the most extreme. Drought drives temperatures higher due to the dry ground. The dry ground and heat creates a high pressure ridge. This ridge keeps the dry conditions going further which drives the temperatures higher....and on and on. 

Water temperatures in the Gulf of Alaska are off-the-charts above average this summer (as it was last winter). 

The above normal Gulf of Alaska water temperatures have enhanced the western high pressure ridge by pushing the jet stream further north. The movement of the jet stream is indicated with the red arrow. The strongest portion of the jet stream (highest winds) is shown with the warmer colors over Alaska. The jet on the east side of the ridge dives southeast in the center of the country and bottoms out over the Ohio Valley where the trough is located.

The PNA index is used to measure these pressure patterns across the Northern Hemisphere. When the PNA is positive, the ridge is very strong out west and the trough/low pressure is strong east as it has been since last winter. You can read about it more HERE. 

The southeasterly jet becomes the conveyor belt for frequent rain and thunder events leading to above normal rainfall across much of the Great Lakes, Midwest and Ohio Valley. This also leads to more frequent periods of below normal temperatures.

For perspective, July in Cleveland, Ohio finished the 6th coolest since 1900.

The average high temperature in Cleveland from July 15th to July 31st was the the second coolest on record!

So the warmer Gulf of Alaska water and the drought out west have significantly boosted the high pressure ridge out west which is reinforcing the trough/cool pattern further east across the midwest and Ohio Valley.  This is not a complete list of the drivers of this summer pattern. The weak El Nino, which garnered a lot of attention during the spring, has had an influence too but not to a major degree. The weak El Nino will factor into our winter outlook which I'll talk about in the fall. Let me know of any other major contributors that I've missed.

Bottom line, it doesn't look like this pattern is going to change anytime soon!