The temperature rose to a record-high 99 degrees today in Boston as Bay State residents slogged through steam bath-like conditions on the sixth day of a sizzling heat wave.

The record was broken at Logan International Airport shortly before 1 p.m. The previous record for the day was 98.

After a warm, muggy night the heat will be on again Saturday, propelling the mercury again into the 90s. Severe thunderstorms will then move in during the afternoon and evening that will whip up strong winds, dump buckets of rain, and hurl lightning. Those storms will usher in a period of cooler weather, forecasters said.

“Lightning, of course, is the biggest threat. These could have some strong damaging winds with them, as well,’’ said Glenn Field, warning coordination meteorologist at the National Weather Service in Taunton. “If you’re under one of the storms, it will be pretty strong.’’


Other hot places in the state today included Westfield and Norwood, which recorded 98 degrees, and Bedford, Fitchburg, Marshfield, Plymouth, and Springfield, which saw temperatures rise to 97.

With the high temperatures combining with stifling humidity, the weather service advised residents to avoid prolonged work in the sun and to instead shelter in air-conditioned environments.

Boston-based Quality Roofing Co. took the advice to heart, giving its workers, no strangers to the blistering sun, the day off.

“It feels like 130 degrees on a roof today,“ said project manager Abdul Yahya. “No crews are roofing today. They are all inside.’’

Boston EMS said that five out of 141 people transported today complained of significant heat-related problems.

Tonight will see a slight chance of scattered showers and thunderstorms, while the majority of the state should stay dry, according to the weather service. Heat and humidity will remain uncomfortable tonight, with temperatures only dropping to the upper 70s.

Temperatures will moderate slightly Saturday, with Boston reaching 94 degrees.

Saturday’s thunderstorms could begin as early as noon in northwestern Massachusetts. Primetime for the rest of the state will be between 2 p.m. and 8 p.m., Field said.

In Southeastern Massachusetts and on the Cape and islands, the storms are expected to arrive on the later side, and much of the day could be good for beachgoing, he said.


“Elsewhere, after 2 or 3 in the afternoon, keep an eye on the sky,’’ Field said.

A cold front will approach the state from the Great Lakes region Saturday evening, bringing an end to the heat wave after seven days. Sunday will be sunny and dry, with seasonable temperatures in the low 80s. Humidity levels will decrease Sunday, with comfortable temperatures in the mid-80s expected through Wednesday.

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