People should use 111 as well as GP and pharmacy servicesWarwick Hospital has said it is under "extreme pressure" following a large flood at its accident and emergency unit.
The service remains available for those who urgently need it, however, the incident has had a "significant impact" on waiting times, it added.
South Warwickshire University NHS Foundation Trust issued the warning just before 15:30 BST on Tuesday.
No injuries have been reported and the trust said its maintenance teams are working to resolve the issue.
It is not yet clear what caused the flood.
People have been urged to use 111 online as the first port of call and access their GPs and pharmacies to help reduce pressure on services.
Those with a life-threatening emergency are advised to continue to call 999.
A spokesperson for the trust issued a reminder that Stratford Minor Injuries Unit is open on Tuesdays, Wednesdays and Thursdays between 09:00 and 17:00.