Boston faces dangerous heat wave: See when it hits 100 degrees this week | Map

Meteorologists say temperatures across Boston and much of southern New England will climb into the 100s later this week ahead of Independence Day celebrations.

Boston and much of New England are bracing for a prolonged spell of dangerous heat as a powerful heat dome settles over the northeastern United States. Forecasters warn that temperatures could approach or exceed 100°F, while humidity will push the heat index as high as 105°F to 110°F in some areas through the Fourth of July holiday.

Youngsters walk by a water mist machine installed by city administration to assist people in coping with the heat on a torrid day, as the National Weather forecaster issued an extreme heat code red warning for most parts of the country, in Bucharest, Romania, Monday, June 29, 2026. (AP Photo/Vadim Ghirda) (AP Photo/Vadim Ghirda)

The National Weather Service has issued an Extreme Heat Watch from Wednesday morning through Saturday for most of Massachusetts and New England, excluding Cape Cod and the Berkshires.

Meteorologists warn that the combination of extreme heat and tropical humidity could pose serious health risks, especially for older adults, children and people working outdoors.

Forecasters said Tuesday will be the most comfortable day of the week, with highs ranging from the upper 70s near the coast to the upper 80s inland.

Map: Heat expected to peak before Independence Day

NBC Boston meteorologists expect Thursday and Friday to be the hottest days of the week. Temperatures could rise to around 100°F across parts of Massachusetts, while the heat index may reach between 105°F and 110°F.

The National Oceanic and Atmospheric Administration's HeatRisk outlook classifies much of Greater Boston under an "Extreme" heat risk by Thursday.

Combined with elevated humidity, the weather could create dangerous outdoor conditions. Overnight temperatures are also expected to remain warm, limiting relief.

What is the heat dome?

According to The Boston Globe, this heat wave is a component of a broader "heat dome," or high-pressure system, that extends from the middle of the nation to the East Coast.

High pressure causes the air to sink, which causes the air to warm up. The warming is more noticeable every day when high pressure remains in one place, and this week will be no exception.

Record temperatures possible across the region

Boston could challenge several daily temperature records during the heat wave. According to the Boston Globe, Thursday's forecast high of around 102°F would exceed the current daily record of 98°F. The city's all-time highest temperature remains 104°F, set on July 4, 1911.

Health officials urge residents to drink plenty of water, avoid strenuous afternoon activity, wear lightweight clothing and never leave children or pets inside parked vehicles.

A cold front is predicted to pass over the area late on Thursday or early on Friday. For part of the July 4 holiday, that system may bring sporadic showers or thunderstorms before cooler, less humid air arrives.