Residents of Harrow and Colchester South are temporarily banned from washing their cars, watering their lawns and gardens, and other outdoor water use.
The Town of Essex is also working with a nearby water supply system in case there's an emergency shortage.
Essex town council said late Wednesday it was declaring a temporary ban for residential customers of the Harrow and Colchester South water treatment plant "immediately, until further notice."
The cause, it said, is "extreme weather events on the shores of Lake Erie," which have caused "a significant reduction in water level."
People are also using more water in light of the warmer weather, the town said in the notice. That's placed "a burden on the system."
Residents should limit non-essential water use as much as possible to reduce the demand on the system, the town said.
The town has also closed the Harrow and Colchester splash pads.
People can check their water bills to see if they're clients of the Harrow and Colchester South water treatment plant.
"It is essential that residents of Harrow and Colchester South suspend the use of outside water as a preventative measure to ensure that we do not experience a severe shortage." Mayor Richard Meloche said in the release.
Essex is also working with Union Water Supply to get more water in case of an emergency.