When a major hurricane or other disaster strikes Martha’s Vineyard, people who need help right away can’t count on getting it from first responders.

“They simply won’t be there when you want them to be there,” said Russ Hartenstine, emergency management director for West Tisbury and a member of the Island Climate Action Network, in a talk at the Oak Bluffs library Saturday afternoon.

In an Islandwide crisis, it will be at least 48 hours before town and regional emergency services are able to assist individuals, Mr. Hartenstine warned an audience of about two dozen Islanders.

“We’re not going to come to your house right away,” because roads will need to be cleared, damage to town property addressed and shelters set up first, he said.

To be safe in a serious catastrophe, Vineyard households will need to rely on their own resources and develop community networks, Mr. Hartenstine said.

“How well do you know your neighbors?” he asked. “If the power’s out, you’re going to need each other.”

He also advised Islanders to sign up on their town websites for emergency alerts by phone, develop plans for both sheltering in place and evacuating and set up a family phone tree to quickly communicate urgent news without tying up local lines and bandwidth.

Climate change is bringing more severe weather events to the region, Mr. Hartenstine said, including two tornado warnings and a tornado touchdown on the Cape over the summer.

“We’re starting to see stuff that we’re not even prepared for,” he said, urging residents to assess their homes’ ability to withstand extreme weather — and to consider evacuating in advance of a storm.

“Evacuation for an Island is really key,” Mr. Hartenstine said. “Think about Puerto Rico. Did anybody there really have resources enough to withstand that? . . . If you’re not helping, you’re a drain on resources. Evacuate.”

The same preparedness talk, was presented at the West Tisbury library earlier this month.

Island Climate Action Network has five more monthly presentations, each of which will be given in both West Tisbury and Oak Bluffs. The network also has a monthly email newsletter.

Next month’s talk, Adapt to the Impact, is set for Nov. 12 at 4 p.m. at the West Tisbury library and Nov. 23 at the Oak Bluffs library.