Collingwood does not have one flood season. It has a different one in each quarter of the year, and each one puts water into a house by a different route. Winter brings ice jams and pipes that split at the thaw. March and April bring the melt. Summer and fall bring the heavy rainstorms. The month tells you which route to check, and the route tells you what the repair and the claim will look like.
The short version
The Nottawasaga Valley Conservation Authority (NVCA) is plain about it on its flood FAQ page: floods in its watershed can come during the spring melt, after major rainstorms in summer and fall, and in winter from rapid snowmelt or an ice jam. That is the whole year.
What changes from month to month is the mechanism. Here it is laid out against the calendar, with the way the water usually reaches a basement.
| Months | What floods | How it reaches the house |
|---|---|---|
| December to February | Ice jams on rivers and creeks, pipes split by a freeze and released by the thaw | Over the ground from a river, or from inside the walls |
| March and April | Snowmelt and rain on frozen ground, rivers high | Over the ground, through the foundation, up the floor drain |
| May to September | Heavy rainstorms and thunderstorms, the bay at its seasonal high | Over the ground, up the floor drain, along the shore |
| October and November | Fall rainstorms, wind pushing the bay onto the shore | Over the ground, up the floor drain, along the shore |
Winter: ice and the thaw
Ice is the part of the calendar people forget. The NVCA’s ice jam page names Collingwood, with Creemore and Avening, among the communities that have had ice jam flooding. A jam backs water up behind it, and the NVCA says the flooding can happen even when river flows are relatively low. It also says ice jam floods have tended to follow rapid weather changes and colder-than-average winters.
The Beaver River showed a close relative of this in January 2026, when frazil ice pushed it up through Clarksburg with no rain at all. That event is written up in full under Beaver River flooding at Clarksburg.
Inside the house, winter has its own flood. A pipe that froze during the cold spell lets go on the mild day after it, which is why a burst pipe at the thaw in Collingwood is its own post on this site. For a closed cottage or chalet, the planning for that belongs in autumn, and the list is in cottage winterizing in Collingwood.
March and April: the melt
Spring is the season the town’s own flood history points to first. Of the two Collingwood floods the NVCA lists on its past flood events page, one is the St. Patrick’s Day flood of 1942. Down the Mad River, a newspaper reported on April 11, 1950 that Creemore had flooded, with two to four feet of water in every cellar in the flooded area.
The melt reaches a basement three ways. River water comes over the ground on a low lot near a watercourse, and whether yours is one is a map question covered in Pretty River flood risk in Collingwood. Groundwater comes through the slab or the wall joint when the ground is saturated. And the Town’s sanitary sewer can back up through a floor drain when melt and rain leak into it, which is set out in the causes of a Collingwood storm sewer backup.
May to September: the storms
The other flood on the NVCA’s Collingwood list is the Victoria Day flood of 1912, so late spring has its own record here.
Summer matters for a second reason. The Pretty River Dike is built around the Provincial Regulatory Storm Event, and the Town’s Pretty River Dike maintenance page gives the 1961 Timmins storm as its example of that kind of storm. The Town’s description is of an afternoon over 25°C, thunder, and a torrential downpour for over an hour late in the evening. That is a summer storm, not a melt. The flood the dike is built for is a rainstorm, not a melt.
In the south of the same watershed, the NVCA records that Adjala-Tosorontio, Mono, New Tecumseth and Shelburne flooded on June 23, 2017, after a single storm.
The bay also rises through these months. Georgian Bay Forever, in its water levels FAQ, says levels usually start low in spring and peak in summer, typically rising a foot or more. It also expects storm surges to lift the bay temporarily on the side the wind blows toward. For a shoreline lot, summer is when the lake is closest.
October and November: fall storms and the shore
The NVCA’s list of flood seasons includes major rainstorms in the fall. The routes are the same as in spring: over the ground near a watercourse, through a wet foundation, and up a floor drain when rain leaks into the sanitary sewer.
On the shore, the NVCA’s flood FAQ describes strong northwest winds pushing water onto the Nottawasaga Bay shoreline during high-water years. A lot on the bay faces that risk in any month the wind blows hard from that side, and a closed cottage has nobody there to see it.
When to book the check
The calendar gives two windows that cover most of it.
Late autumn, before the ground freezes. This one prepares for the melt, the fall storms and the winter.
- Walk the downspouts and move any that drain against the foundation or into the ground beside it.
- Run the sump pump with a bucket of water and watch it empty the pit.
- Find the sewer cleanout, and find out whether the house has a backwater valve.
- Read the declarations page of your policy for an overland water endorsement. The NVCA notes that most standard policies do not cover overland flooding.
- Sign up for the NVCA’s flood alerts, and check the NVCA’s map for your own lot if you are near a watercourse.
- For a seasonal property, book the shutdown.
After the first real thaw, before the main melt. This one catches what the winter did.
- Walk the building with the water on and look at ceilings, exterior walls and the floor around the water heater.
- Look at the basement walls and the slab for new damp patches or tide lines.
- Clear snow back from basement windows and away from the foundation on the low side of the house.
Neither window replaces the other. The autumn check is prevention. The thaw check finds damage that is already there while it is still small.
If the water arrives anyway
Note the date and the route before you clean anything. The route decides which part of a policy responds, and the date lines the loss up against any flood message the NVCA issued that week. For the work itself, flood cleanup in Collingwood covers water that came over the ground, and basement flooding in Collingwood covers water through the walls or slab. How the older buildings and low ground here change the job is covered under water damage restoration across Collingwood.