A Heat Advisory has been issued for much of central Maryland for Sunday July 19. A separate Excessive Heat Warning has been issued for metro Philadelphia. While this may sound alarming, I can imagine some sarcasm from a few people thinking this is July and it should be hot. That is true. But this isn’t the summer of 2012. We have not had temperatures break 90F since June 23. So in part, many of us are not accustomed to this. The bigger news story is how we’ve gone so long ‘without’ having much heat. But there is a little more I want to share with you. At least this is on a Sunday, and not August with football double session practices. Also, with a Code Orange Air Quality Alert, the weekend low traffic should help limit the pollution build up.
My forecast post this morning showed the modeling putting us in the 90s today, but BWI only hit a high temperature of 89F. Still failing to hit the 90s. One reason I believe we have stayed below the mark many times with hot forecast has been the moist ground. After our record rainfall in June and routine storms in July, the ground is more wet than a typical July. Some of the energy is used up evaporating the soil, so we tend to get less hot than expected.
Why is this important? Well, the Sunday forecast range (in Baltimore) is between 95F and 98F. If our recent trend holds true, we might have trouble reaching that high. It will be hot, but maybe not the worst.. if that helps.
The combination of heat and humidity is how your body reacts to the conditions. So even if we were to hit the mid 90s, the dew points in the 70s means high relative humidity. So the calculated heat index forecast could reach 105F.
What Does It Mean?
This might seem like a message from Captain Obvious, but limit your outdoor activities to when it is cooler. If you run or bike, plan to do it in the morning. Maybe consider something else besides that hike, but if you do make sure you bring lots of water to stay hydrated and cool.
Code Orange Air Quality
High sun angle, plus high temperature, but light wind can build up pollution and a recapture to create ground level ozone. That’s the bad stuff. The good ozone is in the stratosphere and location 15 miles above the ground. Down on the ground it can make it difficult to breath, especially for those with respiratory conditions, the young and elderly.
Again, these are all things we’ve had to deal with most summers. But this is the first time this summer, so take it easy.
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