SAN JOSE — The problem of homelessness in the Bay Area turned deadly as Santa Clara County officials announced Friday that four homeless men had died over eight days of hypothermia-related causes, including three in the previous 48 hours as a cold snap sent the region into a deep freeze.

Three of the deaths occurred in outdoor locations in San Jose while the fourth happened in a Saratoga garage.

With more freezing temperatures expected this weekend, nonprofit groups added hundreds of shelter beds and fanned out to the makeshift encampments to implore the South Bay’s thousands of homeless to make use of them. Local homeless advocates said the deaths of so many people in such a short period due to exposure was unconscionable considering the wealth found in the region.

“I’m just angry,” said Jenny Niklaus, the CEO of EHC LifeBuilders, a provider of homeless services. “We have to solve this problem. Even with our cold-weather shelters open, there are still people out there. This is what happens when we allow homelessness to happen.

“People die.”

In a late-day news conference, Santa Clara County sheriff Lt. Dave Lera said all the exposure victims were men in their 40s and 50s, and that hypothermia was a factor in the deaths of each. No other personal information was being released pending notification of families.

The first man was found on Thanksgiving beneath a bridge near downtown San Jose. On Wednesday, the second man was discovered on a sidewalk on Lincoln Avenue near a business.

Then Thursday, a third body was located near Curtner and Canoas Garden avenues, and the fourth was found in a Saratoga garage where a door was open, leaving him exposed.

Also Friday, a man in his 70s was found dead in a camper in the 900 block of Charter Street in Redwood City, although the San Mateo County coroner could not determine if the death was due to exposure or natural causes.

The deaths occurred with the Bay Area in the grip of the first serious cold wave of the season. Temperatures throughout the greater San Jose area reached a low in the mid-20s in the overnight hours Thursday, according to the National Weather Service. The low at Mineta San Jose International Airport was 30 degrees, breaking the previous record of 32 degrees in 1931. Cold weather records were also broken in Livermore, 26 degrees; Mountain View, 33; and Oakland, 37. There was also a rare dusting of snow on San Jose’s Mount Hamilton on Friday evening.

And, more freezing weather is expected this weekend.

“It’s just sad and it’s unfortunate because these really are preventable deaths,” San Jose Mayor Chuck Reed said. “We really need to be getting people into shelter. But the lack of affordable housing has created a longtime problem that now is a short-term crisis.”

The deaths put into stark relief just how dangerous it is to be homeless. It’s not known how many people have died of hypothermia in the county this year. But EHC LifeBuilders and its community partners will hold a ceremony later this month to remember homeless people who have died on the streets of any cause this past year, and Niklaus believes that number is more than 40.

Santa Clara County Supervisor Mike Wasserman, who has been an advocate of funding programs that help get the chronically homeless into permanent housing, said this tragedy proves that more must be done to address the problem.

“People are dying out there, and it’s just wrong,” Wasserman said. “I hope this never happens again. You have to understand that every single person in these encampments is somebody’s son or daughter, brother or sister, mother or father. And yet they’ve been just abandoned.”

EHC LifeBuilders launched the county-funded Cold Weather Shelter Program last Monday night with 275 emergency beds at three sites. After the four deaths, an additional 375 beds were being added through Monday at the Boccardo Reception Center, the former Sunnyvale National Guard Armory and the Gilroy National Guard Armory. The shelters will remain open for an additional two hours each morning.

Also a room will be opened at the Sunnyvale site for homeless people who want to bring their pets. In the past, not being allowed to bring pets has discouraged some people from using the shelters.

Outreach workers from EHC LifeBuilders, InnVision Shelter Network, the Bill Wilson Center and Downtown Streets Team spent Friday combing encampments — often located on creek sides in deplorable conditions — as they handed out blankets and encouraged people to go to the shelters.

Meanwhile, shelters in Berkeley, Oakland, and Southern Alameda County also added beds because of the cold weather.

“We’ve got a cold weekend ahead of us,” Niklaus said. “But the fact is there are more people outside than we have beds. We’re doing what we can, and I don’t want to lose any more people. This is a crisis.”

San Jose/Santa Clara County has the fifth-largest homeless population in the country behind only New York City, Los Angeles, Seattle and San Diego, according to a recent U.S. Department of Housing and Urban Development report.

Of the 7,631 homeless people in the area, who were counted in January as part of a nationwide census, 74 percent were listed as “unsheltered” — meaning they have no place suitable for human habitation to stay. It has been estimated that on any given night, there are 5,000 people who don’t have shelter in the county.

Evening temperatures in San Jose were expected to warm up Friday night and then drop back to around 30 degrees on Saturday night, according to the National Weather Service.

“The question we have to ask ourselves is how many people have to do die?” said Jennifer Loving, executive director of the nonprofit Destination: Home. “It’s cold outside and people can’t survive when it’s freezing. That’s just a fact. This shouldn’t be a surprise to anyone.”

Staff writer Erin Ivie contributed to this report.