When to go
There is really no bad time to visit Montreal. Peak season starts in June and ends in August, when heavy crowds start to form. During this time, accommodation costs and the temperature are high. Montreal reaches highs of 26C, giving the city a pleasant environment to walk around in. There are a number of events and festivals during this time, such as Montreal Pride and the Montreal International Jazz Festival. Outdoor activities will be popular too, including ziplining and hiking.
Sprint / Autumn
If you are looking to beat the crowds but also the harsh winters, visit Montreal during spring (March to May) or autumn (September to November). The weather is pleasant enough to walk around and see the sights, although it might be a little chilly. Autumn is particularly beautiful in Montreal, and accommodation prices are low.
December to February welcomes cold weather, ice and snow. Even though accommodation will be cheap, hotels can become fully booked or close altogether. This is not uncommon, as many establishments close during the winter. However, winter is still a good time to go because there are a number of winter activities to partake in. Seasonal events will pop up so make sure to be on the lookout.
Make sure to research the weather before you travel so you can dress accordingly.