An early summer heat wave is moving into the Eastern US during the week of Monday, June 17. Temperatures will start the week in the 90s and rise to around 100 by the end of the week. The biggest factor will be the heat index, which will make temperatures feel like they are in the 100s. Let’s go over the forecast this week and how hot it will get.

The heat index is the “feels like” temperature which takes into consideration the temperature and dew point. The combination of high temperatures and high dew points makes the air feel hotter and muggier. High heat indices can cause heat-related illness.

• Read more about the dangers of a high heat index and how to calculate it from the National Weather Service (NWS) here!

This week will see a slow progression of hotter temperatures and more dangerous heat index temperatures. High temperatures will start this week in the 90s, rising to the upper 90s and low 100s by Thursday and Friday, continuing into Saturday and Sunday. The heat index throughout the week will be in the 100s through most of the Eastern US.

If you want to relieve the heat, the higher elevations across the Appalachian Mountains and coastal areas will foster some relief. Additionally, a few thunderstorms are possible this week, which could provide some relief with locally heavy rain.

Forecast from Monday, June 17 through Thursday, June 20:

A strong high-pressure system is moving into the Eastern US. This will create favorable conditions for temperatures to rise with the combination of high dewpoints making heat indices hazardous. Below is a look at the NWS hazards map on Monday, June 17 highlighting the dangerous heat coming this week.

Monday and Tuesday will see high temperatures in the upper 80s and low 90s throughout the Eastern US. Dewpoints will be in the upper 60s and around 70, making the heat index in the upper 90s and near 100. The hottest areas on Monday and Tuesday will be through the Ohio River Valley and into southern New England.

On Wednesday and Thursday, temperatures will rise and become more widespread throughout the Eastern US. Temperatures will rise into the mid-90s and around 100 in the Ohio River Valley and southern New England. Heat indices will feel like the low 100s throughout the Eastern US with dewpoints in the 60s and around 70.

• When the dewpoint temperature is in the 60s, the air feels muggy and becomes oppressive around 70 degrees.
• Make sure to use the OpenSnow temperature map to see the latest 36-hour forecast!

Below is a look at the Euro model's forecasted high temperatures on Thursday, June 20. Similar conditions will occur on Tuesday, June 18 and Wednesday, June 19.

The hottest temperatures will be through lower elevations. That means if you want to escape the heat, head to higher elevations where temperatures will be in the 80s with heat indices still in the 90s. Temperatures will still feel very muggy but the higher elevations will provide somewhat of a break. Additionally, coastal areas will stay cooler in the 80s due to the cooler water temperatures of the Atlantic Ocean.

Forecast from Friday, June 21 through Sunday, June 23:

Temperatures will continue to stay hot and continue to rise through the weekend. Temperatures on Friday will be widespread in the mid to upper 90s with low 100s through the Ohio River Valley and southern New England. Dewpoints will continue to stay high in the 60s and around 70.

On Saturday and Sunday, temperatures will cool through New England into the 80s but remain in the 90s and low 100s through the Eastern US. Temperatures are forecasted to reach the hottest yet of this heat wave through the Ohio River Valley with high heat extending into the Mid-Atlantic. Heat indices will be in the low 100s.

Below is a look at the Euro model's forecasted high temperatures on Saturday, June 22. Similar conditions will occur on Friday, June 21 and Sunday, June 23.

Thunderstorms:

Thunderstorms will be possible throughout the week in the Eastern US. Thunderstorms will be scattered, only bringing some rain (locally heavy) and some relief to the heat. The highest chance for thunderstorms will be through the Appalachian Mountains throughout the week and into New England during the weekend.

Below is a look at the Euro model's forecasted rain accumulations from Monday, June 17 through Sunday, June 23. Most of the Eastern US will see chances of thunderstorms throughout the week with New England seeing higher chances into the weekend.

How long will it Last? 

There is growing confidence a storm system could approach the Eastern US from the west on Monday, June 24. The timing and details of this storm are still hard to pinpoint, but if the storm does track through or near the Eastern US, it will move the high-pressure system and heat index away from the Eastern US. This storm will also bring chances of rain and thunderstorms with cooler near-normal temperatures.

Below is a look at the Euro's ensemble predicted upper-level pattern on Monday, June 24 and Tuesday, June 25.

Description: The cool, blue colors show cooler air that will be associated with the storm track moving into the Eastern US. The warm, orange colors show drier and warmer air that will be associated with high pressure.

Cooler temperatures with precipitation chances will come during the week of Monday, June 24. Some areas might stay hot for a few days, but relief is coming!

Thanks for reading!

Zach Butler