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Massachusetts’ first heat wave of the summer is finally over. These graphics show what extreme heat is doing to the state.

A Scituate Fire Rescue crew member takes a moment under the bay of the ER entrance to the hospital.David L. Ryan/Globe Staff

Massachusetts’ first heatwave of the summer, which sent temperatures into the triple digits and wreaked havoc all over the state, mercifully broke overnight on Monday.

For Boston and most of its suburbs, daily high temperatures reached or exceeded 90 degrees Fahrenheit on seven consecutive days.

The heat peaked on Sunday, July 24 when Boston reached 100 degrees by mid-afternoon — a record high temperature for the date.

The heat is not just uncomfortable, but also dangerous. During multi-day stretches of high heat, Boston Emergency Medical Services typically experiences a 15 to 20 percent increase in daily calls, a spokesperson for the department said. From Wednesday, July 19 through Monday, July 25, the agency experienced a 15 to 30 percent increase in the daily call volume with over 400 incidents each day.


Thanks to climate change, Massachusetts is experiencing more, and more intense, heat waves. If daily high temperatures do reach 90 degrees through Sunday, it would only be the 15th time that Boston has seen more than five consecutive 90-plus degree days since record keeping began in 1872, NOAA’s data shows.

If the world doesn’t take major steps to curb carbon emissions, the frequency and severity of heat waves will increase.

From 1971 to 2000, the average summer in Massachusetts saw four days over 90 degrees. By mid-century, climate scientists say the state may have 10-28 days over 90 degrees each year.

Here are three graphs that show the effects of this heat wave — and global warming — on Massachusetts.

People are using more electricity

Amid sweltering heat, residents tend to use more electricity to power their air conditioning. As high temperatures crept into the 90s each day, electricity consumption crept upward, according to the grid operator, ISO-New England.

Thanks to climate change, we have more hot days — and nights

If it you feel like Massachusetts is seeing more hot days, you’re right. Data from the Northeast Regional Climate Center at Cornell University shows that 90+ degree days are becoming more common in the Boston area.


Heat waves aren’t just about how high the temperature gets—it’s also about temperatures not dropping after dark. Summer nights are getting hotter as climate change progresses, and the incidence of summer nights where the temperature stays above 70 degrees is on the rise. Northeast Regional Climate Center figures show that’s the case in Boston.

Dharna Noor can be reached at Follow her on Twitter @dharnanoor.