Wikipedia said its servers automatically shut themselves down to avert heat damage, CNN reported.
"This problem was quickly resolved, but unfortunately it may take up to an hour before access is restored for everyone, due to caching effects," the site's blog said.
The navigation error message many users found when trying to access the site was fixed a few hours after the initial shutdown, and the site appeared to be in working order by 4:30 p.m. EDT, CNN said.
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'
Beyonce flaunts bikini body, Blue Ivy in vacation pics