This year, the dog days are so scary, as part of the early summer start rarely brings much relief. Statewide, this June and July combined is our 12th warmest summer start since 1895 and warmest since 2016.
Temperatures aren’t just isolated here in North Carolina. In the west, our colleagues at the Oklahoma Mesonet recognize an arduous achievement on July 19, when all 120 of their weather stations reached at least 102°F.
Of course, we’re protected from such triple-digit coverage across the state thanks to a cooler climate in our Mountains and along the coast, as we described in Curious Coast’s blog post series.
But it did make us wonder: has our entire state been above, say, 80 degrees at once?
In this edition of Climate Cities, we’re hunting for the warmest hours ever across North Carolina.
Our most recent warmest hour
An obvious starting point for our search is Mount Mitchell – our state’s highest peak and often the low bar for statewide temperatures.
With a climate more similar to southern Ontario than to the southeastern United States, the average summer of Mount Mitchell high temperatures, in the mid-60s, were cooler than average low over most of Piedmont and the Coastal Plain.
That means the best candidates for our warmest hours will come from a small subset of Mount Mitchell’s hottest days.
Ours ECONet Station on Mount Mitchell began hourly observations in late June 2008, and in the 14 years since, its highest instantaneous temperature was 81.3°F at 2:49pm on July 1, 2012. However, the temperature there dropped a few degrees to 3 o’ hours, and in any case, Mount Mitchell was Not the coolest place in the state at that timeas showers north of Piedmont left Oxford at just 73°F, and nearby Henderson-Oxford Airport at 77°F.
However, the previous afternoon, we saw our warmest hour in the hourly observation era. In 6 pm June 30, 2012Mount Mitchell is sitting at 78.8°F while Grandfather Mountain, 33 miles northeast, measured an hourly temperature of 78.6°F at the mile-high swinging bridge.
This summer, our warmest hour was at 4 p.m. on June 15. At that time, Grandfather Mountain reported a temperature of 72.9°F, while our other high-altitude locations including Mount Mitchell and the Highands are at 74°F or higher.
Several Outer Banks websites also report cooler temperatures, including 74.8°F in Duck and 75.2°F in Oregon Inlet, but in between, most of the state is in a steady range over the years. 80s top or low of the 90s on that mid-June afternoon.
While the June days between 2012 and 2022 were certainly warm, they didn’t quite meet the criteria for the entire state to rise above 80 degrees at once. However, by digging deeper into the past, we can find many possibilities for such occurrences.
Daily profile search
Since 1925, and beyond the roughly 15-year gap in its data from 1965 to 1980, the National Weather Service Collaborative Observation Station on Mount Mitchell made observations of daily temperature and precipitation.
This location has measured many state records, including our coldest temperature (-34°F on January 21, 1985), the biggest snowstorm (50 inches in March 1993), and the wettest calendar year (139.94 inches in 2018).
Current Mount Mitchell viewing site and its predecessor reported a maximum daily temperature of at least 80 degrees on 15 occasions, helping to narrow the dates to be considered.
Of course, it’s not the only site that can cause a potential hot hour. As we’ve seen in more recent examples, depending on factors like cloud cover and wind direction, other mountain locations can even be cooler than Mount Mitchell, while showers are scattered. or sea breezes could lower temperatures across other parts of the state.
Our search became even more complicated because we did not have long-term daily observations from many of these immediate mountaintop or coastal locations. Instead, we will have to use the clues provided by the nearby stations.
For example, Grandfather Mountain tends to be 7 to 10 degrees cooler than Boone and 4 to 6 degrees cooler than Banner Elk, where we do There are long historical observations, while Mount Wayah Bald is generally cooler than Cullowhee and Franklin at elevations of 10 to 15 degrees.
That means we’ll need to look at the dates when nearby lookouts were doing well in the ’90s, which almost guarantees that the peaks are in the ’80s.
After applying that logic and scouring historical records from across the state, we’re left with a top contender from nearly a century ago.
Our warmest historical hour?
From 1925 to 1927, Carolinas are in deep drought nearly a decade before the Dust Bowl era was better known in the Midwest.
It’s been a challenging time for farmers, already struggling to stay profitable after World War I subsidies ended and European farms re-emerged on the continent. Global market. Adding to the problems of local farmers is the appearance of the fruit borer, a pest that has devastated cotton crops. Drought was another challenge, and it effectively wiped out the yield of three consecutive growing seasons.
That drought is also an important part of the temperature rise, even after the end of the summer climate. As surface water sources such as soil and streams dry up, less moisture can evaporate from them to form water vapour, or humidity that normally regulates our climate compared to areas like Oklahoma.
By early September 1925, one wide area of high pressure The deep south caused temperatures to soar more than 100 degrees, and warm air entered western North Carolina. Even Marshall in the mountains climbed to 100°F on September 8, which is still the latest point of the year that the spot has hit triple digits.
Three days earlier on September 5, Mount Mitchell reached a peak of 81°F under clear skies. In Ashe County, Parker reaches 91°F, and the observer there note in monthly comments that it was “the hottest September ever known in this section.” Statewide, September 1925 still ranks as the 2nd highest temperature on record.
Elsewhere in the Mountains, highs on September 5 reached 92°F in Banner Elk and 97°F in Cullowhee with smoky skies. That Local observers reported “All crops suffer greatly from drought” in September, with “lowest springs and streams ever known.”
With widespread warmth in the western part of the state, it’s more likely that peaks like Grandfather Mountain were at least in the low 80s. In additiona second area of high pressure Grows in eastern North Carolina limiting showers and thunderstorm activity. The coolest coastal site in Southport still hit a temperature of 81°F that day.
Because the temperature in early September tends to maximum from 2 to 4 pmwe will consider September 5, 1925, at 3 p.m. the most likely time of our state’s warmest hour, probably all of North Carolina rising above 80 degrees for a short period of time that afternoon.
If that doesn’t happen then, it will have another chance the next day, when Mount Mitchell hits 81°F again and all other lookout points across the state report maximum temperatures of 81°F. 85°F or higher on September 6.
All in all, the combined effects of a prolonged drought, a building block of sweltering air from the west, and cloudless skies made for a particularly stifling pair of afternoons 97 years ago. In the early days of September 1925, there was little relief to be found from the heat, no matter where you went in the state.
And while our warmest hours occurred under exceptional circumstances nearly a century ago, North Carolina continues to be warm today. The North Carolina Climate Science Report records some historical trends toward our daytime highs, but an upward trend in nighttime lows, which poses an increasing public health risk.
Also, in the nearly century since 1925, we’ve certainly had some hot summer days, including state record high was 110°F on August 21, 1983; Raleigh’s local record is 105°F, tied four times since 2007; and our rarity the beginning of october is a hundred degrees hot in 2019.
For its durability alone, 2022 also deserves a mention among our warmest. As of August 11, Raleigh has recorded 61 days of temperatures at or above 90 degrees in 2022, the 2nd highest for this time of year and just one day behind the sweltering rate set. established in 2011.
In the future, climate models show the whole day and Nighttime temperatures will rise across the state, including in the Mountains, likely to see three to six times hotter days per yearwith temperatures reaching at least 90°F, by mid-century.
With those changes in mind, our next potential warmest hour could be on the horizon.
