Tuesday, October 13, 2020

How "Cool" Was September? The Complete Recap

September in northern Ohio started off with cooler temperatures and almost record setting rainfall on Labor Day. Radar loop is below.

More than 30% of the area saw 3"+ inches of rain.

Rainfall was significant the first half of the month.

Second half of the month was abnormally dry across most of the state

Cleveland went 14 days without rainfall:


Normally, extreme northeastern Ohio receives the most rain in September

Even with an extremely dry second half of the month, most climate divisions montly rainfall ranked very high.

Eastern US rainfall during the first 8 days of September:

Eastern US rainfall from September 8th through September 21st:  Notice the heavy rain from the numerous tropical systems along the gulf coast

This was the first September since 2009 without a 90 degree day. Overnight lows by the middle of month dropped into the mid 40s


Mid-September record lows were set across the Great Lakes and New England

Northern Ohio temperatures the morning of the 21st

Center of the cool temperatures was in the middle of the US through the 15th. It shifted southeast by month's end.

This was the coolest September for northern Ohio since 2014.

The graphic below show the number of days with high temperatures above normal historically in Cleveland. The last 5 years had the MOST above normal September days. The only period of time close was the late 1940/early 1950s. 

A closer look shows how unusually cool the day-to-day temperatures in September were in Cleveland. I tabulated the above/below normal days for the last 5 years:

We ended up with 5 straight days with high temperatures in the 60s. Here is the frequency of consecutive days in the 60s in September. Last time we had a stretch like this was in 2010!

September cloud cover was well below normal in 2020. We went almost 11 straight days with clear skies!

Compare 2020 with 2019...BIG increase in cloud cover vs this year.

Now 2018...

Nationally, look at the difference between this year's mid-September temperatures vs normal (September 8 - 21) versus last year and the last "cool" September back in 2014




Overall most of the country had near/slightly below normal temperatures in September 2020