When one side of the Lower 48 is dealing with hot weather, it tends to be relatively cool on the opposite end. Not this week. Heat domes situated over both corners of the contiguous United States on Tuesday promoted record-high temperatures in the Northeast at the same time the Pacific Northwest sizzled amid unprecedented temperatures.
Numerous records were set across New England and parts of the Mid-Atlantic region on Tuesday. Both Boston and Hartford, Conn., hit 99 degrees, each setting high marks for the date. Newark matched its highest temperature recorded in June. Records extended from the eastern Great Lakes region to Maine.
There’s one more day to go. More than 11 million people are under excessive-heat warnings in parts of Delaware, New Jersey and Pennsylvania on Wednesday. About 35 million are under a heat advisory in the broader region. A cold front is set to quash the heat Thursday into Friday.
An Excessive Heat Warning is now in effect for most of NE NJ. Heat index values of 105 to 107 are possible in these locations. The rest of the area, besides SE Suffolk County, remains under a Heat Advisory and can expect heat index values of 100 to 104. #NYCwx #NYwx #CTwx #NJwx pic.twitter.com/zyG3JBmbQH— NWS New York NY (@NWSNewYorkNY) June 30, 2021
The extreme heat by the numbers
Several locations in the Northeast neared or surpassed the century mark Tuesday. That’s quite unusual for June and led to some monthly or near-monthly records.
- Boston’s 99 degrees was good enough for the second-hottest June day on record, and the hottest at the observation location at Logan International Airport. It tied a record set in 1933.
- Newark reached 102 degrees, tying the June record set in 2011, 1994 and several years prior.
In addition to the monthly marks, numerous record highs for June 29 were set. Below is a sample across the Northeast:
- Hartford reached 99 degrees, topping 98 in 1934.
- LaGuardia in New York reached 98 degrees, tying 98 in 2012 and 1959. A record-warm low of 81 also was set, making it the second-warmest June low on record there.
- Providence, R.I., reached 97 degrees, topping 96 in 1934.
- Rochester, N.Y., reached 94 degrees, topping 93 in 1948.
- Augusta, Maine, reached 94 degrees, topping 90 in 1997. A record-warm low of 72 also was set.
- Binghamton, N.Y., reached 91 degrees, topping 90 in 2012.
- Erie, Pa., reached 90, tying a mark set in 1948 and several prior years.
A number of locations in the Eastern US broke or tied their June 29th high temperature records. The 102 degrees at Newark NJ ties the record for the entire month of June (most recently 6/9/2011). The last time Newark reached at least 102 was July 18, 2012 when the high was 104. pic.twitter.com/TAwCOoPxes— NWS Eastern Region (@NWSEastern) June 29, 2021
Additionally, a number of record-high low temperatures for the date were established as temperatures remained uncomfortably toasty at night.
What’s causing this heat?
A relatively unusual configuration of weather systems has promoted record highs in the Northeast and the Pacific Northwest simultaneously. As a stagnant and exceptionally strong heat dome has roasted the Pacific Northwest, called an “omega block” because of its shape, a weaker heat dome in the western Atlantic has supplied hot air along the East Coast.
Heat domes are zones of high pressure that essentially bake the air beneath them.
Some research suggests the rapid warming of the Arctic appears to be making meandering and wavy jet stream patterns, conducive to the formation of such heat domes, more common. Although not as extreme as in the West, drought conditions across parts of New England may be enhancing the heat there, as well.
Given the weaker heat dome affecting the Northeast and an approaching cold front, the intensity and duration of the heat wave won’t come close to rivaling the event in the Pacific Northwest. Wednesday is the last day of potential record heat in the region.
Still, additional records are in the forecast Wednesday in the zone from roughly Philadelphia to Boston as highs again reach the mid-90s to about 100. Some records in jeopardy include those in Boston, where a forecast of 98 degrees would top the record of 95, and at La Guardia, where the predicted 99 degrees would top the record of 97.
Even up into Atlantic Canada, Nova Scotia is dealing with a second day of heat warnings, with highs near 90 expected.
The cold front that will pass the region on Thursday is expected to produce some wild temperature swings.
A weather station near Springfield, Mass., may be looking at a record cool day Friday in the front’s wake. The station, Westfield-Barnes, is expected to hit 96 degrees on Wednesday, topping the previous June 30 record high of 93. On Friday, the forecast there is 73 degrees, which would come close to the lowest high for the date — 72 in 2009.
In the forecast graphic above from the Weather Service office in Boston, the lower temperatures on the way help form what looks like a smile — perhaps fitting as this punishing heat fades.