Baby it's hot outside

June 7, 2008 12:39 PM Email| Comments (0)| Text size – +

By John M. Guilfoil, Globe Correspondent

Hazy. Hot. Humid.

In what could be a full-fledged heat wave, Boston could see 90 degrees this afternoon. The region will face near record-breaking heat Sunday, Monday, and Tuesday with the heat index expected to break 100 degrees on Monday before a “cold front” brings 80 degree days toward the end of the week, forecasters say.

Hartford and Springfield will be hottest, with temperatures of 98-99 degrees on Monday and a heat index of up to 104 for a short time.

"Beginning tomorrow [Sunday], we’re looking at highs in the 90s," says Kim Buttrick, a meteorologist for the National Weather Service in Taunton.

The worst (or best, depending on your outlook) of it will come on Monday, when Boston’s record of 96 degrees set in 1984 could be in danger, Buttrick says.

Dew points, which measure water’s ability to evaporate into vapor, are going to be increasing, Buttrick says. High dew points combined with high temperatures mean high humidity. High temperatures induce people to sweat, which cools us down. But when it is humid, that sweat can’t evaporate as fast. When it is hot and humid, we don’t cool off, our bodies can’t regulate our temperature as well, and we overheat, Buttrick says.

The heat index measures the combined effects of the temperature and the dew point/humidity on people in the same way wind chill measures the effects of cold. The temperatures may be in the 90s, but if we can’t cool down from sweating, it will feel much hotter to be outside for extended periods.

That’s when the danger of heat stroke and exhaustion come into play. Buttrick recommends fluids and light clothing and cautions against caffeinated beverages and alcohol, which worsen dehydration. “We all love our coffee and iced coffee, but even if you have iced coffee, you need to replenish yourself with 1-2 glasses of water,” Buttrick says.

The weather service has not issued a heat advisory, but the state Department of Environmental Protection has issued an air quality alert, in effect from 2 p.m. today through 10 p.m. Sunday.

The weather service defines a heat wave as three or more consecutive days of 90+ degree weather. A heat advisory is issued when an area can expect daytime heat indices of 100-104 degrees for two or more consecutive hours.