A heavy downpour saw Manx emergency services called out "numerous times" to deal with flooding on Monday night.
The Isle of Man Fire Service said it attended reports of floods in Douglas and Castletown, while police said parts of Crellin's Hill were left "unsafe" after being "broken up" by the rain.
A Met Office spokesman said 1.8ins (46mm) of rain fell in 24 hours, mostly in the two hours before midnight.
He said this sort of downpour that only happens "once every 10 years".
A spokesman for Isle of Man Constabulary added that the top of Crellin's Hill to Finch Road in Douglas would be closed "for a few days".