Local blood supplies have bounced back from dangerously low levels over the holiday season, but bad weather, a catastrophic event or even the reemergence of the flu virus could set back inventory levels, underscoring the need for continuous donations, experts say.

An overnight snowstorm kept donors away from the Community Blood Center’s five locations in Dayton, Hamilton, Middletown, Springfield and Richmond, Ind., last Friday, cutting blood donations that day by about 40 percent, according to Mark Pompilio, a spokesman for the blood center. He said they try to collect between 300 and 350 units of blood each day to meet the needs of the 24 hospitals it supplies in its 15-county coverage area.

“We had several (blood) drives canceled last Friday because of the icy weather, and it was just dead around here because no one was going to drive” to make a donation, Pompilio said.

He said the day was eerily reminiscent of the week of Christmas last year when the blood centers collected only 604 units of blood for the entire week, forcing officials to reach out to donors directly by email and through social media outlets.

“We went through a very difficult holiday period,” Pompilio said. “We had to go outside our region to get blood, especially type O blood because we were particularly low on that. It was not an emergency, but it was definitely not a good situation.”

Pompilio said it’s always a challenge to collect blood during the holidays because people travel and schools let out for vacation, postponing major blood drives. It was even more difficult to maintain supplies during the past holiday season because severe winter weather forced the cancellation of already scheduled blood drives and the demand for blood was higher than usual, resulting from a rash of patients with internal bleeding, among other factors. The severity of the flu season also played a role.

“You have to be healthy to donate,” Pompilio said. “If people show up and they have a little fever or other flu symptoms, they can’t donate. That’s a typical winter thing. But this flu season was really tough, especially around Christmas.”

Donations are up since the beginning of the year, and the Community Blood Center on Monday reported at least a 14-day supply.

But blood supplies will remain in jeopardy as long as winter lasts, Pompilio said: “We’re looking very good right now, but we always need donations.”

Nationwide, the American Read Cross — which supplies about 40 percent of the nation’s blood supply — says it’s having no problem keeping up with demand but has had to move blood around the country to augment blood donations interrupted by recent weather events.

“We’ve been doing that successfully, so we’re not in any kind of emergency,” said Karen Kelley, a spokeswoman for the Red Cross’ Great Lakes Division. “But the need for blood is ongoing, so we would encourage anyone to donate blood as they are able to.”