OTTAWA -- Environment Canada says a lot of rain is on the way.

A rainfall warning has been issued for Ottawa-Gatineau and much of eastern Ontario.

Rain is forecast to develop early Sunday morning and continue through most of the day. There is a chance of thunderstorms in some parts of the region.

Environment Canada says anywhere from 25 mm to 40 mm of rain is possible. Totals will be greater in areas that experience thunderstorms.

Since the ground remains partially frozen, Environment Canada is using its winter threshold of 25 mm or more for the warning, saying the soil has a limited ability to absorb large amounts of rain.

Localized flooding in some low-lying regions is possible.

The rainfall warning is in effect for the following regions:

  • Ottawa North-Kanata-Orléans
  • Ottawa South-Richmond-Metcalfe
  • Gatineau
  • Merrickville-Wolford-Kemptville
  • Westport-Charleston Lake
  • Brockville-Prescott
  • Gananoque-Mallorytown
  • Maxville-Alexandria
  • Cornwall-Lancaster
  • Winchester-Newington
  • Morrisburg-Long Sault
  • Prescott and Russell
  • Smiths Falls-Perth-Eastern Lanark County

The 3:30 p.m. forecast calls for rain to start overnight. The low is 3°C. 

Sunday's forecast calls for showers with a risk of a thunderstorm in the afternoon. Rainfall totals for Ottawa could reach 20 mm to 30 mm. The high Sunday is 10°C.

Showers are expected to continue Monday. The high 7°C.