The organizations said the drop comes after the country faced record-breaking heat and as more people go on vacation for the summer.
All blood types are needed, however type O blood is specially low.
"It's critical hospitals have both type O positive and O negative blood ready to go for patients in the most life-threatening situations," said Dr. Eric Gehrie, executive physician director for the Red Cross. "Type O is especially important for victims of accidents and other trauma who are receiving emergency treatment."
Those who donate blood, platelets or plasma in August will get a $20 Amazon.com gift card, the Red Cross said.
Red Cross offering Amazon gift cards in August as donations drop dangerously low
There are multiple blood drives happening in Chicago this week:
Monday: American Red Cross Chicago Chapter at 2200 West Harrison Street from 8 a.m. to 1 p.m.
Tuesday: At 150 N Riverside Plaza from 10 a.m. to 3 p.m.
Tuesday: Cook County Headquarters at 69 West Washington, Daley Center from 9 a.m. to 2 p.m.
Tuesday: Advocate Illinois Masonic Medical Center at 814 W Nelson Ave from 9 a.m. to 2 p.m.
Wednesday: At 120 S. LaSalle from 9 a.m. to 2 p.m.
To make an appointment visit RedCrossBlood.org or call 1-800-RED CROSS.