An extended heat wave begins in Boston on Tuesday

Boston so far this year has seen two days hit 90 degrees or higher (June 26 and July 1), but that's about to change. Hot air comes to the region Tuesday, and the heat will be here for an extended stay.

It's likely the city will be coping with a six-day-long heat wave. That's nearly a week of temperatures reaching 90 degrees or higher.

Typically, Boston averages about 15 days a year with such highs. In 2021, Boston recorded four heat waves, the longest of which occurred between June 5-9. We also saw 24 days at 90 degrees or higher last year, including a day in which the city hit 100 degrees.

Over 100 years ago, back in 1912, Boston endured its longest stretch of consecutive 90-degree days in history: nine in a row.

There is a chance the wind will be light enough, particularly on Wednesday and Thursday, to allow a weak sea breeze to kick in at Logan Airport (where the official Boston weather data is taken) and hold us just shy of 90. It will be close.

Interestingly, summertime heat records are hard to beat, and this stretch is no exception.

So we know it’s going to be hot, but how humid will it be?  Our dewpoint temperature measures the amount of moisture in the atmosphere, and it will be sticking in the uncomfortable range. Combined with the heat, "feels like" readings will be in mid- to upper 90s each afternoon. A heat advisory was issued for Wednesday and will likely be extended.

During hot and humid weather, the body's ability to cool itself is affected. Under normal conditions, your skin, blood vessels and perspiration level adjust to the heat. But these natural cooling systems may fail if you're exposed to high temperatures and humidity for too long, you sweat heavily and you don't drink enough fluids. The most common heat-related illnesses are heat stroke, heat exhaustion, heat cramps and heat rash.

With this much heat and humidity in place, some thunderstorms will be possible, though right now the risk looks fairly isolated and very hit-or-miss in nature. The greatest chances for some pop-up action will be Thursday afternoon and Saturday, so keep an eye to the sky and seek shelter indoors should a storm head your way.