Boston prepares for a major heat wave

A long-lasting, record-breaking heat wave is enveloping large parts of the country this week, including Massachusetts.

Why it matters: Extreme heat is the number one weather-related killer in a typical year.

• Human-caused climate change is making heat waves more likely, longer lasting and more intense .

State of play: Mayor Michelle Wu declared a heat emergency, and a National Weather Service heat advisory takes effect in Boston noon Tuesday until 7pm Friday.

Zoom in: The city opened 14 cooling centers at Boston Centers for Youth & Families buildings.

• The cooling center will ask visitors to sign in with their name and contact info.

Wu and Gov. Maura Healey urged residents to keep hydrated, stay in the shade and, if helpful, find a pool or spraydeck to cool down.

Protip: The state has a list of spraydecks, pools and other swimming areas you can search by city, town or zip code.

Zoom out: A heat dome is building across the Ohio Valley and lower Great Lakes and will likely shift east-northeastward this week.

• The heat dome could potentially peak at record intensity for New England at this time of year.

Threat level: According to WeatherBELL Analytics, by Sunday, about 265 million people from Chicago to Boston to Washington, D.C., are forecast to see air temperatures reach or exceed 90°F, with many of them experiencing heat indices of about 105°F.

• Even northern Maine, which typically is just emerging into warmer conditions at this time of year, is likely to see temperatures soar into the upper 90s°F this week.

NWS forecast offices are pointing to the long-lasting nature of the heat wave as a cause for concern.

• They also cite its timing so early in the season and societal factors — some schools are still in and the federal Juneteenth holiday occurs on Wednesday — as increasing the risks of significant human health impacts.

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