Extreme Temperature Diary-Saturday July 18, 2020/ Main Topic: Prolonged Historic U.S. Heat Wave…Update #14: Excessive Heat Arrives On East Coast

Saturday July 18th… Dear Diary. The main purpose of this ongoing blog will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Main Topic: Prolonged Historic U.S. Heat Wave…Update #14: Excessive Heat Arrives On East Coast

Dear Diary. Today excessive heat in association with this historically long heat wave has finally arrived in the East Coast. Not that it hasn’t been toasty in the Megalopolis cities already this summer- Washington D.C. suffered through a near record long streak of 90°+ max heat from late June through this week. Now all of the East Coast’s big cities will approach 100° through early next week. Whether or not we see many records there remains to be seen.

As usual to start this blog let’s access U.S. heat levels for the next two days. Our CAT 2 heat wave from yesterday is increasing in strength today because it is expanding eastward. Heat advisories have been added by the National Weather Service across much of the East and continue in the Midwest from Saturday:

On Sunday heat will continue to intensify on the East Coast with most locations seeing maxes from 95-100 along with high humidity. A front will end most of the excessive heat for the Midwest. Heat levels will be about the same across the South as felt on Saturday. We won’t see my CAT 3 designation, though, because most areas will not see many record or above record temperature values from major stations with long periods of record keeping:

Today, for a change, I’m going to repost yesterday’s article from my friends at the Washington Post, detailing what is in store for the East the next few days:

https://www.washingtonpost.com/weather/2020/07/17/triple-digit-heat-threatens-dc-dangerous-conditions-are-set-envelop-mid-atlantic/

Capital Weather Gang

Triple-digit heat threatens D.C. as dangerous conditions are set to envelop the Mid-Atlantic

The exceptional heat will pair up with sweltering humidity to create potentially deadly heat indexes.


Highs on Monday as forecast by the National Weather Service. (Pivotal Weather)

By Matthew Cappucci andAndrew Freedman July 17

Exceptional heat will affect the Mid-Atlantic beginning this weekend, bringing temperatures in the upper 90s to near 100, with heat indexes reaching hazardous levels of up to 110 degrees. The District could see the air temperature reach the century mark by Tuesday, as some of the warmest air since 2016 moves in early next week.

Tropical humidity will exacerbate the already toasty temperatures, the sauna-like warmth keeping nighttime temperatures from providing relief, which poses health risks to anyone without access to cooling, especially vulnerable populations such as those with preexisting medical conditions and the elderly.

The heat wave is coming on top of the coronavirus pandemic, with a recent uptick in cases of the novel coronavirus in Virginia, Maryland and the District, complicating public health planning.

[Blistering heat and humidity to intensify in central, eastern U.S. this weekend]

The community spread of the coronavirus presents complications for communities seeking to provide cooling shelters for residents, especially since the heat will target some of the same groups that are experiencing disproportionate impacts from the illness, including poorer residents, minorities and the elderly.

The regional breadth of blistering heat is part of a larger area of unusually high temperatures that encompasses the central and eastern portions of the Lower 48. On Friday, heat advisories and warnings stretch from the Dakotas down to Texas and eastward into Indiana. In states such as Iowa, moisture evaporating from crops across the Corn Belt will contribute to building extreme humidity, amplifying the heat to bring heat indexes topping 110 degrees.

Locally, the National Weather Service has already hoisted an excessive heat watch for much of New Jersey, eastern Pennsylvania and northern portions of the Delmarva Peninsula. Peak heat index values between 105 and 110 degrees are possible in these areas during the Sunday through Tuesday period. The NWS may issue a heat advisory for the DMV on Monday, forecasters stated.

The heat will also affect New York City, but the Big Apple looks to remain on the periphery of the atmospheric torch aimed to its south.

About 283 million Americans could see high temperatures top 90 degrees during the next week, while more than 20 million could see highs top 100 degrees during the same period.

Local heat could will go from uncomfortable to dangerous

Capital Weather Gang

The exceptional heat will pair up with sweltering humidity to create potentially deadly heat indexes.

Exceptional heat will affect the Mid-Atlantic beginning this weekend, bringing temperatures in the upper 90s to near 100, with heat indexes reaching hazardous levels of up to 110 degrees. The District could see the air temperature reach the century mark by Tuesday, as some of the warmest air since 2016 moves in early next week.

Tropical humidity will exacerbate the already toasty temperatures, the sauna-like warmth keeping nighttime temperatures from providing relief, which poses health risks to anyone without access to cooling, especially vulnerable populations such as those with preexisting medical conditions and the elderly.

The heat wave is coming on top of the coronavirus pandemic, with a recent uptick in cases of the novel coronavirus in Virginia, Maryland and the District, complicating public health planning.

[Blistering heat and humidity to intensify in central, eastern U.S. this weekend]

The community spread of the coronavirus presents complications for communities seeking to provide cooling shelters for residents, especially since the heat will target some of the same groups that are experiencing disproportionate impacts from the illness, including poorer residents, minorities and the elderly.ADVERTISING

The regional breadth of blistering heat is part of a larger area of unusually high temperatures that encompasses the central and eastern portions of the Lower 48. On Friday, heat advisories and warnings stretch from the Dakotas down to Texas and eastward into Indiana. In states such as Iowa, moisture evaporating from crops across the Corn Belt will contribute to building extreme humidity, amplifying the heat to bring heat indexes topping 110 degrees.

Locally, the National Weather Service has already hoisted an excessive heat watch for much of New Jersey, eastern Pennsylvania and northern portions of the Delmarva Peninsula. Peak heat index values between 105 and 110 degrees are possible in these areas during the Sunday through Tuesday period. The NWS may issue a heat advisory for the DMV on Monday, forecasters stated.

The heat will also affect New York City, but the Big Apple looks to remain on the periphery of the atmospheric torch aimed to its south.

About 283 million Americans could see high temperatures top 90 degrees during the next week, while more than 20 million could see highs top 100 degrees during the same period.

Local heat could will go from uncomfortable to dangerous


Maximum heat indexes forecast by the National Weather Service through Wednesday. (NWS)

The elevated temperatures stem from a strong, sprawling area of high pressure anchored over the Tennessee Valley, also referred to as a “heat dome.” Beneath it, sinking air will warm well into the 90s. Dew points, meanwhile, will climb above 70 degrees. Dew points are a measure of how much moisture the air contains; and dew points in the 70s make the air feel oppressive.

In the D.C. area, the clockwise flow around the high pressure will bring westerly winds, which will further elevate air temperatures by causing air to spill over the Blue Ridge and sink to lower elevations. That compression increases its air pressure, and in turn its temperature — allowing for further warming.

The sweltering weekend could feature highs in the upper 90s for D.C. both Saturday and Sunday, with the National Weather Service forecasting a 100-degree high on Monday. The heat index, which is measure of how hot the air feels to the human body, could be as high in the DMV as it will be in Phoenix, thanks to the copious amounts of moisture in the air along the East Coast.

The heat is going to be noteworthy for both its severity and endurance. Highs in the upper 90s could linger through at least the mid week, with the only relief coming from periodic afternoon showers and thunderstorms. Adding insult to injury, the heat wave follows D.C.’s second-longest stretch of 90-degree days, which ended Thursday when the high temperature at Reagan National Airport only reached 87 degrees.

“Monday [is] looking to be the hottest day next week with triple digit readings certainly possible across portions of the metros and northern Virginia,” wrote the National Weather Service in Washington. “Combine this with dew points in the low to middle 70s, [and] heat indexes will likely be hovering near Advisory level range both Monday and Tuesday.”


Dew points on Sunday as simulated by the American GFS model.

Regardless of whether the District hits the triple digits on Monday, it will still fall shy of a daily record. The city managed a remarkable high of 106 degrees on July 20, 1930. However, D.C. hasn’t snagged a 100-degree reading since 2016, when temperatures hit the century mark on three consecutive days between August 13 and 15.


A beautiful summer scene along the C&O Canal in Georgetown. (C JRCook/Flickr) (JR COOK/Flickr)

In many years, extreme heat is the number one weather-related cause of death in the United States, topping tornadoes and hurricanes. In addition, heat waves are one of the clearest manifestations of human-caused global warming, with studies pointing to an increase in both the occurrence of these events as well as their severity.

The elevated overnight temperatures forecast during this heat event, with low temperatures remaining near 80 degrees in Washington on Sunday and Monday nights, poses a particular health risk. Exceptionally warm and humid nights prevent the body from experiencing a respite after a long, hot day, and this can more quickly lead to dehydration and heat-related illness.

Due in part to human-caused climate change, overnight temperatures are warming faster than daytime highs, which can prove especially problematic for urban residents who lack air conditioning. During this heat wave, people may be hesitant to go to cooling shelters for fear of contracting the coronavirus.

The long-range outlook does not offer much hope for a respite, either. Despite some moderation in temperature, above-average temperatures look to dominate much of the country for at least the next two weeks, if not longer.

Matthew CappucciMatthew Cappucci is a meteorologist for Capital Weather Gang. He earned a B.A. in atmospheric sciences from Harvard University in 2019, and has contributed to The Washington Post since he was 18. He is an avid storm chaser and adventurer, and covers all types of weather, climate science, and astronomy. Follow 

Andrew FreedmanAndrew Freedman edits and reports on extreme weather and climate science for the Capital Weather Gang. He has covered science, with a specialization in climate research and policy, for Axios, Mashable, Climate Central, E&E Daily and other publications. Follow 

As usual, I’ll be posting more updates on this dangerous heat wave as the day progresses.

Here is one “ET” from Saturday:

Here is more climate and weather news from Saturday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:

(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.) 

Guy Walton… “The Climate Guy”

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