Thursday, June 20, 2024

Late June Heat...For How Long?

Our first heat wave in northern Ohio since 2021 continues. The long range outlook picked up on this pattern change a few weeks prior to the start.

June started out dry but with "cooler" daytime highs in northern Ohio. June 10 was 61 degrees with low 40s for overnight lows. Then a two day "teaser period" of warmth then the first of a weeks worth of 90+ degrees starting on June 16.

You can see how the high pressure ridge (Bermuda High) expanded across the eastern seaboard to near record high levels starting Monday June 17. By the weekend, the heat ridge (dome) gradually dissipated as the ridge flattened in the deep south.

The position of the ridge east of Ohio allowed a few "weak fronts" (disturbances) to clip the southern Great Lakes with small but potent storms with heavy rainfall. Future radar from Thursday June 20 to Saturday June 22.

Rainfall totals from June 16 to June 19:

Heat Advisory was issued from Monday through Saturday across northern Ohio.

Heat Advisories and Excessive Heat Warnings extended into Michigan and New England.

Tuesday high temperatures were running well above normal eastern US with well below normal temperatures across the west.

Northern Ohio heat index forecast was showing 100+ in spots where storms didn't develop.

The last time we had a heat index 100+ was in 2022. We measure the heat index in total hours.  Here are the totals since 2012 with the warm summers of 1995 and 1988 for reference.

Dew points at/above 75 degrees only occur in small periods this far north. We reach this level June 19. We average around 2 days with humidity levels this high each summer. 2019 was the last summer with above normal of days with dew points at/above 75°.

Anytime we experience extreme weather, people will compare the current conditions to past events they remember. Stretches of heat like this elicit memories of the summer of 1988.  However, there are big differences between 2024 heat and 1988 heat.

The 2 week period where we reached 100° degrees (this was the last time) featured some cool overnight lows. In fact, we broke four low temperature records starting three days AFTER we broke the all-time high temperature record of 104°

Look at June 20, 1988 high temperatures across the US.  

Now high temperatures on June 19, 2024

Another note about the summer of 1988 in northern Ohio.  We reached 90° 35 times. Only 14 of the 35 days at/above 90° had a dew point at/above 70° (tropical) and only 5 of the 13 days at/above 95°.  So plenty of 90s with relatively lower humidity that summer.

Will this heat continue?   Expect a break as the heat shifts to the central US.