The Joint Typhoon Warning Center upgraded Champi to tropical storm status early Friday, with sustained winds of 40 miles per hour. The system was about 825 miles east of Guam, moving west at 12 miles per hour, with a typhoon watch in effect for Guam, Rota, Tinian and Saipan.
Forecasters warn that even a slight change in the storm's track could significantly affect wind and rainfall conditions across the islands.
The latest threat comes as the region continues to recover from super typhoons Sinlaku and Bavi, which caused widespread damage earlier this year, and Tropical Storm Choi-wan earlier this month.
American Red Cross coordinating officer Charles Blake said repeated storms had stretched disaster response capabilities.
"When you get hit with multiple storms, one right after the other, and you don't get time to fully recover from those storms, there's going to be some gaps," he said.
The Red Cross is deploying approximately 85 additional personnel from Guam, Hawaii and the US mainland to assist with evacuation shelters and disaster response operations. Shelters are being prepared across Saipan, Tinian and Rota.