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Think it's hot today? Just wait...

E-mail|Link|Comments () July 5, 2010 02:14 PM

By Peter Schworm, Globe Staff

As temperatures in the Boston area surged into the 90s for the second consecutive day, weather forecasters delivered some unwelcome news - enjoy it while you can.

Tomorrow is expected to bring dangerous heat and humidity to much of the state, with the mercury climbing near triple digits in greater Boston. The heat index - a measure of how hot the air feels when factoring in relative humidity - will likely rise to unusually high levels.

"Tomorrow is going to be rough," said Eleanor Vallier-Talbot, of the National Weather Service in Taunton. "People need to take it easy, and it will be best to be in an air-conditioned building."

The most recent forecasts call for temperatures to reach 94 in Boston tomorrow, and the heat will be even more intense inland. Highs could reach 98 in Bedford, and 99 in Norwood.

The culprit is a large high-pressure system that is drawing warm, muggy air from the south, Vallier-Talbot said. While yesterday and today's low humidity, coupled with a light sea breeze, have helped take the edge off the heat, tomorrow's air will be stiflingly thick and sticky.

"It's going to feel a lot worse," she said.

The Weather Service will likely issue a heat advisory, urging people to limit their time in the heat and stay well hydrated. State environmental officials today issued an air quality alert south of Boston for elevated ozone levels, and hazier skies are expected tomorrow.

In Boston, officials are planning to open cooling centers across the city if needed, and have notified elderly residents the temperatures could reach dangerous levels. Those who need assistance can call the city's hotline at 617-635-4500.

Assuming temperatures reach 90 degrees, tomorrow would mark the first official heat wave of the summer. There have been eight days of 90-plus degree days in Boston this year, including June 28-29. Average temperatures in June were about two degrees above normal.

While tomorrow's weather will be unpleasant, relief could be on the way. Forecasters had initially expected temperatures to remain scorching all week, but a rare low-pressure area developing in the North Atlantic could be enough to bring a cooling sea breeze, beginning Wednesday.

But residents in central and western Massachusetts should brace for more steamy weather.

"Inland, it's going to be hot," she said.

Peter Schworm can be reached at schworm@globe.com