A heat wave and Fourth of July crowds have resulted in a flurry of medical issues that kept Island emergency responders busy this week.

“The weather has hit people hard no question about it,” said Tisbury fire chief John Schilling. “And it came out of nowhere.”

He said the Tisbury emergency medical services team responded to 24 calls in the first four days of July, double the number of calls from the same time last year. He attributed some of that increase to the heat.

“People are falling, they get weak and dizzy,” he said.

Oak Bluffs fire chief John Rose said he was seeing a similar uptick.

“We’ve been busy,” he said. “The heat’s definitely a factor.”

The sheriff’s office also reported an increase in medical calls over last July.

Dr. Aaron Hexdall works in the emergency department at the Martha’s Vineyard Hospital, where he said he is seeing multiple cases of heat exhaustion, sunburn and dehydration.

He said when it comes to heat, prevention is key.

“We do see a lot of people passed out from heat exhaustion, and our big recommendation is just to go slowly. If you feel weak, just go to a cooler place.”

He cautioned people to drink plenty of water, use high SPF sunscreen and wear protection from the sun.

The July heat wave brought temperatures in the 80s on the Island, but was relatively mild compared to the mainland. Elsewhere in New England, temperatures spiked above 100 degrees.