More than 470 units of blood could not be collected due to blood donation center closures, cancelled blood drives and the inability of donors to attend blood drives this week thanks to the cold, icy temperatures, Red Cross officials said Wednesday.

“Donors are encouraged to donate as soon as possible after conditions have improved enough to allow for safe travel,” said Evan Duffy, communications manager for the Red Cross. “There is a special need for type O and type B blood donors.”

Duffy said all volunteer donors in the months of January, February and March will be entered into a regional drawing for one of two pairs of round-trip Delta Air Lines flights as part of the “Help Save Lives and Take to the Skies” promotion.

“The need for blood is constant – it doesn’t stop because of the weather,” Evans said.