Multnomah County officials on Monday morning said they suspected that four people died from the heat over the holiday weekend. Three of them were county residents and another died in Portland but wasn’t a resident, officials said.

As is typical, the county’s Medical Examiner released few details of the deaths. One person was found dead on Friday and two others were found dead on Sunday. All three died in zip codes in Southeast Portland, and at least one died east of Interstate 205. Southeast Portland has far less tree coverage than Portland’s west side does, so temperatures on the east side of the river are regularly more deadly during heat waves.

A fourth person died in a Portland hospital of suspected heat-related causes, but officials say the person wasn’t a county resident.

The county operated cooling shelters across the region over the weekend and three of the shelters will open at noon on Monday. Cooling shelter locations can be found here. Volunteers are still needed at the shelters.

Temperatures are expected to remain elevated until at least Tuesday.