We’ve gotten some meaningful though streaky rain in the past few days, with 1 to 4 inches in many locations, and locally more than that in parts of Southside Virginia.
It is of course not enough in and of itself to end the long-term severe to extreme drought across our region, but it could be a start if it’s followed by other intermittent rain in weeks and months ahead. This particular showery spell looks to mostly dry up by Thursday and Friday.
We’ll revisit our rain and drought fortunes again in weeks ahead, but for the moment, let’s turn to a different aspect of the summer ahead: How hot might it be?
Meteorological summer starting cool
Summer begins Monday, June 1, on the meteorological calendar, in which seasons are rounded off to the start and end of calendar months rather than following the traditional astronomical pattern of equinoxes and solstices.
This meteorological summer looks to begin on the cool side, with perhaps some 40s-50s lows and mostly 70s highs for a few days next week.
An “omega block” pattern with a high pressure ridge in the central U.S. and a deeply south-diving jet stream looping down on either side near the Pacific and Atlantic coasts will allow for some transport of cool air unusually far to the south in the Eastern U.S.
While long hot, dry periods have been common in our region this spring, the persistence of cold air in eastern Canada and the northeast U.S. has brought on occasional punches of much cooler air, and could be a limiting factor for heat waves in our region if that continues to happen into summer.
There may be some even more far-ranging reasons this summer has a chance to be relatively cool on the whole.
The role of a developing El Niño
A couple of weeks ago in this space, we explored what the likely development of El Niño, the irregularly recurring stripe of warm sea surface temperatures in the equatorial Pacific, could mean for Southwest and Southside Virginia weather in months ahead.
Amid the caveats about how El Niño is only a part of the weather picture and how it is more of a discernible factor in our winter weather than in summer, I dropped this line hinting at possible summer effects.
“El Niño and La Niña correlations to summer weather are weaker than those in colder months, but it can generally be said that summers with an El Niño or are transitioning to El Niño are typically not among our region’s hottest.”
Let’s flesh this out a bit more statistically.
Taking a fairly quick look at eight prior summers in which either La Niña was transitioning to El Niño or a strong El Niño was already building in the equatorial Pacific, it’s really quite striking how frequently these summers ranked toward the cooler end of the spectrum based on June 1 to Aug. 31 average temperatures.
The eight summers considered with a somewhat similar progression in the equatorial Pacific to what is expected were those in 1965, 1972, 1976, 1982, 1997, 2009, 2015 and 2023.
That list happens to include what was the coolest summer on record at Lynchburg (1997, 71.1 degrees) and Roanoke (1972, 71.7 degrees), each with more than a century of consistent weather data and tending historically to average toward the middle of temperatures across Cardinal News’ broad Southwest and Southside coverage area.
None of the eight summers were anywhere near the warmest few on record at those two locations, with the warmer ones tending to rank toward the middle.
The warmest two were the most recent ones at Roanoke, 2015 at 76.0 degrees and 74.8 degrees in 2023, but those were cooler than most of the others in a spate of recent summers that have been consistently warmer than most of those of the past.
Roanoke’s coolest summer of the past 20 years and Lynchburg’s second coolest in the same period was 2009, one of the summers on this list.
Each of the listed summers before 2000 rank among the top 20 coolest all time at both Roanoke and Lynchburg. And several of these summers with a developing El Niño appear among the coolest on record at other locations in our region.
At Danville, 1972 is the sixth coolest summer, 2023 is the 7th coolest, and 1965, 1976 and 1997 are among the 20 coolest dating back to 1917. At Martinsville, 1965, 1972, and 1997 are among the top 10 coolest summers, and at Wytheville, 1972, 1976 and 1997 are among the few coolest summers going back nearly a century at both locations.
Without more rigorous research and statistical analysis, these observations fall short of a solidly established correlation between developing El Niños and cooler summers, but there is clearly enough of a propensity to expect that the odds may tilt to at least a not-terribly-hot summer in the months ahead — if El Niño intensifies as it’s expected to.
What about rain this summer?
Summer 1972, Roanoke’s coolest, happened to be Blacksburg’s fourth coolest and Lynchburg’s eight coolest, but it was also 11th wettest at Lynchburg (18.72 inches), 19th wettest at Blacksburg (15.85 inches) and 23rd wettest at Roanoke (15.06 inches).
By contrast, seven years earlier, the 1965 summer headed toward a strong El Niño was among the driest on record — 14th at Lynchburg (6.74 inches), 21st at Roanoke (8.65 inches).
On the whole, however, there does not appear to be any significant parallels between El Niño development and any consistent direction on summer rainfall in our region. Some are wet, some are dry, most are in the middle.
The heavier 1972 rainfall figures were skewed upward by the flooding rains from the inland track of Hurricane Agnes’ remnants in June 1972.
Ironically, El Niño often leads to a lesser quantity of tropical cyclones in the Atlantic basin during the fall, but late fall through early spring are often wetter in much of the southern U.S., frequently edging into Virginia, because of an enhanced subtropical jet flow.
As for our summer, there is no solid reason to expect either drought-ending rains or definite worsening of drought solely from the potential development of El Niño.
Summer heat prediction contest coming
Next week, we’ll begin taking guesses from readers in the annual Cardinal Weather summer heat prediction contest.
The task there will be different and largely detached from what we have discussed. Predicting what the hottest temperature of summer will be at given locations is not necessarily directly correlated with how hot or cool a summer is on average.
A cool overall summer can have a couple of extremely hot days. A hot summer on average can have a lot of low to mid-90s highs and without any near 100.
Be on the lookout for the start of this contest next week.
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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