It was pretty hot that last week in July! I downloaded the meteorological data from Taskinas Creek, VA from the CDMO and plotted that heat wave in Fig. 1. July 24th through the 28th exceeded 95°F each day! Luckily, by July 29th, the daily high dropped by 10° to be “only” 85°F.
Besides heat, parts of the Mid-Atlantic also had a terrible downpour on July 30th, which resulted in the tragic flooding of Ellicott City, MD. I also plotted the precipitation from Jug Bay, MD to visually show this rain event (Fig. 2). On July 30th, as recorded at Jug Bay, 0.45 inches of rain fell, 0.35 inches in just 1 hour!
Extreme Weather: Heat Matters Too!
We all know that weather can be dangerous. That is why we know to go inside during a thunderstorm or to seek shelter in a tornado warning. We hear about hurricanes and blizzards usually with enough advance to get the appropriate supplies or to evacuate.
But we probably think less about heat.
Looking at the 10 and 30 year averages, heat is actually the number one cause of weather-related fatalities (Fig. 3). We only need to remember back two weeks to recollect how extreme heat can make you weak, easily dehydrated, and achy just from being outside for a few minutes! And not everyone is luckily enough to have AC and plenty of ice water at the ready.
Nighttime Heat can be Dangerous
I choose this week’s topic based on a CNN post that caught my eye.
“Unusually high humidity will keep nighttime temperatures very warm, which can be more dangerous than the daytime highs, because our bodies don’t have time to recover. The temperature needs to drop to at least 80 degrees for recovery to begin.” – Jennifer Gray and Dave Hennen, CNN Meteorologists
To further support this, the National Weather Service states: “The common guidelines for the issuance of excessive heat warnings is when the maximum daytime index is expected to reach 105, and the nighttime low temperature does not fall below 75 or 80 degrees.”
The Tropical Night index is the annual count of days when the coolest daily temperature is still greater than 68°F. In Chesapeake Bay, we have observed between 2 and 4 additional days per decade of these near-dangerous warm nights, and that trend is projected to continue increasing by 3 to 8 days per decade in the next century.
The annual amount of really warm nights has increased in the near-shore Chesapeake Bay region, which could be hazardous to anyone without access to AC or to young children and the elderly. As we move into the future, warm nights should be considered as dangerous weather!