Daily Record Highs Fall as Heat Dome Grips the Eastern U.S.

A persistent heat wave across the central and eastern U.S. will peak on Tuesday, sending the mercury into the triple digits for some of the nation's most populated urban centers. Here is a look at the record-breaking temperatures so far, as well as when you can expect to find relief from the heat.

All-time Records Have Already Been Smashed as Heat Wave Persists

The heat dome that set up over the central U.S. this past weekend has now become fully entrenched over the East Coast. The building heat dome will deliver the hottest temperatures of the season for the busy Interstate 95 corridor from Boston and down through New York City, Philadelphia, Baltimore, and Washington, D.C. The increase in the humidity levels will amplify the heat.

It has already been a dangerous stretch of weather for the East Coast. All-time daily record highs have fallen over the last few days across the Midwest and into the Northeast. School officials in Paterson, New Jersey, had to cancel a high school graduation ceremony midway through the process when several people had to be sent to hospitals for treatment of heat-related illnesses.

How hot has it been? The community of Plattsburgh, New York, reached a high of 101 degrees on Monday. This reading was good enough to tie the all-time record for any day in this town.

Baltimore's Inner Harbor recorded a high of 104 degrees on Monday. Not only was this a sizzler by any standard for this part of the country, it was also only two degrees lower than the country's top reading of the day. That distinction belonged to Death Valley, California, with a top reading of 106 degrees.

The heat made its way up into New England to start the week. Burlington, Vermont, recorded its toastiest day in nearly 24 hours when the mercury soared to 99 degrees.

Daily low readings have also fallen this week. The town of Ipena, Michigan, saw its previous daily low record of 77 degrees be replaced with a reading of 79 degrees on Monday. It was even warmer overnight in Eau Claire, Wisconsin. This city's overnight low of 82 degrees on Sunday beat the prior record of 81 degrees.

What to Expect in the Hours Ahead

The scorching temperatures have prompted the National Weather Service (NWS) to issue extreme heat warnings and advisories for a large part of the lower and middle Mississippi valleys to the east to the Atlantic seaboard. Based on recent changes made to the alert system, extreme heat warnings are now the highest level of heat alerts. Cities under this top alert include Boston, New York City, Philadelphia, Washington, D.C., and Raleigh.

More records are likely to fall on Tuesday across the Northeast. Some communities could set records for any day in June for daily high and overnight low readings. Most of the major cities along the Interstate 95 corridor in the Northeast are bracing for highs that crack the century mark.

You have to go back to July 18, 2012, to find the last time that New York City's Central Park recorded a reading in the triple digits. It is looking likely that the Big Apple will hit this benchmark on Tuesday. It has been even longer since Philadelphia has seen this barrier in the month of June, going back to 1994.

As noted earlier, the oppressive humidity coming along for the ride will elevate the real feel readings even further. Dew points that climb into the 70s will translate to extremely muggy conditions. The heat index is forecast to easily reach the triple digits across the mid-Mississippi Valley, the Ohio Valley, the South, and the East Coast. This steamy weather will linger through the middle of the week.

The higher humidity levels will also work to keep overnight temperatures elevated. For instance, some cities and towns will fail to see the temperatures dip below the 80-degree mark overnight. Without proper cooling when the sun goes down, it will be challenging for homes without air conditioning to escape the dangerous conditions.

When to Expect Relief

The extreme heat will linger into Wednesday for most of the Northeast. The temperatures will finally trend noticeably downward on Thursday. For example, New York City will fall from a high of about 100 degrees on Tuesday into the upper 90s on Wednesday. Thursday's forecast is calling for a high of just 77 degrees. The arrival of rain showers on this day will go a long way to trim the heat. It will be even cooler on Friday in the metro area with a forecast high of 72 degrees under cloudy skies.

The unseasonably warm temperatures could hang on through Thursday for a large swath of the Appalachians and the mid-Atlantic. The mercury will dip lower by the end of the work week in this area, however, it will still feel like the middle of summer.

The mid-Mississippi and the Ohio valleys will experience stifling heat and humid conditions into the weekend. For instance, places such as Cincinnati will continue to see readings in the 90s through Friday. The mercury will fall slightly on Saturday, topping out with highs in the upper 80s. This is also when the region will begin to see a higher chance of rain showers and thunderstorms. We will monitor this part of the forecast as the weekend approaches.

The unseasonable temperatures are the result of a powerful bubble of high pressure anchored in the higher levels of the atmosphere. This pattern has created the stubborn heat dome over the eastern half of the country.

The sinking air falling near the middle of the heat dome naturally suppresses the development of clouds. The absence of clouds paves the way for the intense June sunshine to heat the ground and the air circulating above.

In addition, the southerly and southwesterly winds are bringing up the hot and humid air typical for this time of the year across the southern U.S. and ushering the heat up into the Midwest and the Northeast.

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