The Red Cross is sending out a call for blood donations. Over the past month, the organization said its blood supply fell by 25%.

There’s been a decrease in donations, according to Bethany Bray Patterson, a spokeswoman for the Red Cross’ chapter in the D.C. area.

“Particularly there is an emergency need for Type O,” Bray Patterson told WTOP. “Unfortunately, we have had to restrict the amount of Type O that we are giving out to hospitals right now because of the shortage.”

That could present problems for patients in critical need of care. Dr. Eric Gehrie, executive physician director for the Red Cross, said in a statement that hospitals need to have both Type O positive and O negative blood on hand.

“Type O is especially important for victims of accidents and other trauma who are receiving emergency treatment,” Gehrie said.

Bray Patterson said the group has seen a shortfall of about 19,000 units in July.

The shortage is not terribly surprising because so many regular donors leave for vacation, she said. But weather is also playing a factor. Around 100 blood drives across the country were canceled due to extreme heat and around a half dozen of them were canceled in the D.C. area due to scorching temps, according to the Red Cross.

“Blood is a very sensitive thing and needs to be kept at a specific temperature to maintain safety,” Bray Patterson said. “When temperature is higher than what is safe, including indoors, sometimes when the air conditioning just can’t keep up, we do have to close drives early or cancel drives.”

While the summer months have brought about a slump, blood donations overall have dropped 40% over the last 20 years, according to the Red Cross.

“The pandemic, of course, was a big factor because we do so much blood collection out in the community,” said Bray Patterson.

The Red Cross is requesting anyone with a spare hour to come donate at one of many blood donation centers across the D.C. area.