Relief is expected tonight from the Island's first significant heat wave of the year. Forecasters are predicting the heat wave, which has sent thousands to the beach and created long lines for ice at Vineyard stores, will likely end tonight with the arrival of a cold front from Canada.

Temperatures in the last two days have hit the 90s in the shade, which is rare for the Vineyard. The last time the thermometer at the National Weather Service Cooperative Station in Edgartown hit the 90s was on July 8, 1999.

"We are having a hard time keeping up," said Bonnie Barrow of Nancy's Snack Bar in Oak Bluffs, which has been turning out between 500 and 800 bags of ice each day for Islanders. "We haven't had a heat wave like this for years."

Jesse Steere, owner of Shirley's Hardware, said electric fans are a hot item this week. He ordered 300 electric fans of varying sizes. "I think we have 60 left," he said yesterday. "People are buying things for the grill, they are buying beach umbrellas, anything to go the beach," he said. "We are selling fans. They are coming up from the cellar like crazy."

Marshall Carroll of Menemsha Texaco said: "We are selling plenty of Gatorade and water." Fortunately, Mr. Carroll added, "There is always a breeze here. If there isn't a breeze here, there isn't one anywhere."

"People are very thirsty," said Jamie McNeely, manager of Our Market in Oak Bluffs.

In years past when it was this hot, the electric power companies issued brownout warnings. Not this summer. "There's plenty of electricity," said Margaret Norton of Nstar, the regional electric distribution company. There are some supply issues on the Cape, she said, but not on the Vineyard.

The hot weather may be great for tourism, sending many to the beach, but it has caused serious concerns for Island animal control officers. Barbara Prada, Edgartown's animal control officer, has received a couple of calls about animals locked in cars. "The temperature in a car can get up to 160 degrees in no time, even if there is a window partially open," she warned.

In her 18 years as an animal control officer, she said, "I have only had police break into two cars."

At Alexander's Air Conditioning and Refrigeration, the crews are working extra hours. "It's crazy busy," said Laurel Vettl, office manager. "The owners and the workers are out there nonstop. The guys are working really hard, and they do a great job," she said.

Meanwhile, it's hot in the office where she works. "I did purchase a fan for myself," she said.

Michael J. Henry, a meteorologist for Weather Services Inc. in Lexington, said the heat wave will end tonight as a line of thunderstorms approaches from the north and west. "Friday will be hot and humid, but there maybe some comfortable conditions in south coastal Massachusetts," said Mr. Henry. "I think the front will tend to stall over southern New England, generating fog and showers for this weekend. The temperature will be in the upper 70s."

The heat wave was caused by a large Bermuda high settling over the ocean south of the Vineyard. "Basically it all began last week, last Thursday and Friday. It was hot and humid. We had a cold front generate thunderstorms on Saturday," Mr. Henry said.

Some parts of the Vineyard got nearly inch of rain in less than an hour late Saturday morning. The National Weather Service station in Edgartown measured .93 inches.

Once the front passed, temperatures continued to rise. On Wednesday the temperature on Martha's Vineyard was higher than in Boston. Yesterday the temperature at the Martha's Vineyard Airport was 91 degrees. It was 96 in Boston, 99 in Providence and 96 in Plymouth.

Mr. Henry said: "I bet the relief arrives in the form of thunderstorms [tonight]. The weather will then hang around for a couple of days from Saturday through Monday."