Parents might want to think about incorporating an umbrella into their kids' Halloween costumes.
Environment Canada said it expects that it will be rainy across southwestern Ontario when trick-or-treaters hit the streets on Thursday evening.
The wet conditions will move into the region on Wednesday and continue throughout Thursday, with between 25 to 50 mm of rain possible by Halloween night.
"People are going to hate my forecast and hate me afterwards," Environment Canada Meteorologist Gerald Cheng said with a laugh. "People are hoping for some dry weather, especially for trick-or-treating so they can really show off their costumes, but it is not going to be like that. There will be showers lingering, especially in the early evening hours."
The national weather agency issued a special weather statement for much of southwestern Ontario on Wednesday due to the amount of rain and windy conditions expected over the next couple of days.
Cheng notes it is not unusual for Mother Nature to rain on everyone's Halloween fun.
"This is really the season where we get those big systems so when you get the rain it will last at least 12 hours, unlike in the summer when you get a thunderstorm it's over in an hour," said Cheng. "[Trick-or-treaters] will need to make sure their costumes will work with the rain."
There is a silver lining to this year's Halloween forecast - temperatures will be mild. Daytime highs from London to Windsor will be at or near double digits and will remain above the seasonal average low of 1.5 C at night.
"There is a lot of cloud cover, so the cloud cover will act like a blanket," said Cheng.