Whether you define summer’s arrival by the sunlight of the solstice, the tidy climatological starting point of June 1, or simply whether it’s hot enough to spend time at the pool with iced tea, there’s no doubt we’re in the thick of it now.
But this summer’s hottest day is probably still ahead of us.
So far this year, Richmond’s hottest high was 94 degrees on June 4. It would be unusual if we didn’t get to at least the upper 90s.
A reader, Charles Hunter, recently emailed with a question:
”What is the statistical hottest day of the year? I remember that a few years ago you wrote about the hottest period of the year, in mid-July (9th through the 19th.) Just curious if there is a hottest day.”
Mid-July is indeed our statistical high point of hot weather, and that’s true by a few ways of looking at it. Based on the climate of recent decades, Richmond’s normal daily highs peak at 90 degrees between July 1 and July 24, while the normal lows plateau at 69 degrees between July 4 and Aug. 5.
But the weather patterns of any given year can result in the actual hottest day happening anytime from May to September.
Over the past 80 years of records at Richmond International Airport, July 23 brought the peak heat more often than any other date: five times. There are four-way ties for July 9, July 15 and July 22, showing that there’s still plenty of variability in the data.
The earliest instance of the hottest high of any year was on May 13 in 2000. But there’s a technicality: That day hit a mark that was then tied on June 12 and again on July 10.
The latest date for peak heat in a year was Sept. 9, 1946. Similarly, it matched a high that was first hit on June 9 that year.
If we look at hottest seven-day periods instead of single days, a healthy range can still be found throughout history.
Most often, Richmond’s hottest week hits in July. But there have been rare times when the hottest seven-day spell was as early as May and as late as September.
Not every year sees us reaching triple digits. But when we do, the days with the greatest frequency of 100-degree readings are July 21 and 22. Both dates each had seven 100-degree-plus highs in records dating to 1897.
Fittingly, our hottest high of 2019 was 100 degrees on July 21. But there was a drought-aided surge to the upper 90s in early October.
Richmond’s all-time highest reading of 107 degrees occurred on Aug. 6, 1918.