In Harvard Square, try Au Bon Pain or Rebecca's Cafe for decent versions.

Advantages: Cool.

Disadvantages: Sometimes the lemonade is too sweet. Sometimes there's too much ice.

Variations: Other cold drinks, such as iced tea or iced coffee, can also cool you off.

4. Whale watch. Not only cool, but educational. The ocean and wind will cool you off, and the whales will wow you.

Many whale watch boats cruise out of Lynn, Gloucester or Cape Cod, but one of the best whale watches departs right from Boston Harbor. Run by the New England Aquarium, the cruises depart daily at 11 a.m. and 5 p.m. Reservations are recommended (call 9735281), and the prices are a hefty $23 for adults, $18.50 for college students.

Take the T from Harvard Square to the Aquarium stop on the Blue Line. (Or take the Red Line to South Station and walk along the Harbor toward Rowe's Wharf and the Long Wharf Marriott. The New England Aquarium is right there.)

Advantages: You'll be cool for the whole day.

Disadvantages: You may get seasick.

Variations: Skip the boat ride and just hung out in the Aquarium and look at the fish in the big tank. It's air-conditioned.

5. Beach: A classic hot-weather escape. Two ocean beaches are easily accessible by T: Wollaston Beach, on the Red Line; and Revere Beach, on the Blue Line. Revere Beach is the bigger of the two.

Commuter rail and a walk will take you to Walden Pond, made famous by Harvard's own Henry David Thoreau, Class of 1837.

Advantages: A swim will cool you off. Revere Beach has camp value. Walden is transcendental.

Disadvantages: Crowds, the hot sun, screaming children, cigarette butts in the sand, sunburn.

Variations: The nicest beaches in the area are on Cape Cod and up near Cape Ann. Getting there by public transportation is a challenge, however.