Weather on the Fourth of July is often described as “hot as a firecracker.” This one will be that, perhaps more so for some in our region than any previous Independence Day.
A “heat dome” high pressure system is building over much of the central and eastern U.S. this week, leading to a significant to major heat wave that will result in widespread 90s and 100s high temperatures.
For the Southwest and Southside Virginia coverage area of Cardinal News, temperatures approaching or even slightly exceeding the 100-degree mark are likely starting on this Wednesday afternoon as this posts and continuing into the weekend for lower-elevation areas, including the Roanoke Valley and locations east of the Blue Ridge.
Even some of the places a little higher up to the west of the Blue Ridge will likely reach the 90s. Dew points in the 50s and 60s will make it feel a few degrees hotter to the human body than the air temperature, as sweat is not as easily condensed in more humid air.
Chances of showers and storms step up over the weekend, and there are indications of a wetter and at least somewhat cooler pattern setting in by next week.
But first, the holiday heat wave.
Triple digits surprisingly rare on July 4
There will probably be some record highs set, including possibly on Independence Day itself, which is Saturday.
One reason for that would be that there is an odd historical tendency for July 4 to not be one of the hotter days during other hot spells this time of year going more than a century back.
It has proven to be a day with a real reticence to cross the triple-digit line in the generally hotter parts of our region.
Take Danville. In its observed weather data going back to 1917, Danville has hit 100 degrees at least once on every single date in July, except one: July 4. The hottest it has been on Independence Day is 99 in 1919. It made it to 98 on the Fourth two years ago.
The hottest July 4 for Roanoke came in 1999, when it reached, appropriately, 99. July 5 and 6 made 100, but not July 4.
A seemingly hard-to-miss opportunity to reach triple-digits on fireworks day in the Star City would have been in 2012, the heat wave surrounding the infamous derecho. Each day except one between June 28 and July 8 reached at least 97, and four topped 100. July 4 was not the single day that didn’t reach 97, but it was one of the days that “only” reached 97 during that heat wave.
Lynchburg and Martinsville haven’t even really almost hit 100 on July 4, each peaking at 98, in 1966 and 1999, respectively.
After some digging when it looked like it was possible that no Cardinal News country locale had ever recorded 100 on the Fourth of July, I found Mecklenburg County’s Clarksville reached 101 on July 4, 2012, and the nearby John H. Kerr Dam scraped 100 two years ago in 2024. Because these are volunteer co-op stations, their periods of record for each day run 8 a.m. to 8 a.m., so the high temperatures for July 4 get recorded as July 5.
There’s a pretty good chance at least one other location in our region will see its first 100-degree July 4 temperature this weekend.
A different kind of holiday booms
One thing that can stymie high temperatures on any given day is thunderstorm development.
High pressure is likely to be strong enough aloft, with a warm stable air mass high in the atmosphere that will resist updrafts, that thunderstorms development will be minimal or non-existent in our region through at least Friday.
Never say never when it is this hot, though.
Any time it is as hot as it will be with some moisture in the air, there is a always at least a “silent 5 percent” chance of storms even when forecasts don’t specifically say so. If there is any kind of difficult-to-detect weakness in the high pressure, or enough moisture convergence or temperature differential along a weak atmospheric boundary or our region’s steep terrain, the heat can sometimes force an updraft sufficient to fire isolated storms.
There is also some potential for storm clusters to form to our west and northwest and move into our region, especially as the heat dome high pressure begins edging westward over the weekend into next week.
So as you go about your Fourth of July festivities, be mindful of both the need to take cool breaks and hydrate with extremely hot temperatures, and also the need to have a plan in mind to move indoors quickly if thunderstorms develop or move toward your location.
Journalist Kevin Myatt has been writing about weather for 20 years. His weekly column, appearing on Wednesdays, is sponsored by Oakey’s, a family-run, locally-owned funeral home with locations throughout the Roanoke Valley.
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