Get out your umbrellas!
Environment Canada says southwestern Ontario could get up to 55 mm of rain by Wednesday morning.
The rain expected to start late Tuesday afternoon and continue overnight.
The agency said the showers could be heavy at times, with a possibility of thunderstorms.
Some areas could get more than 50 mm of rain.
The warning includes Waterloo Region and Guelph, as well as all areas between Tillsonburg, Listowel, Oakville, Innisfil and Coburg.
Environment Canada said the rain will ease up by Wednesday morning.