Can someone please tell me what type of weather I can expect if I visit Montreal and Quebec City in July, August, or September?

Both cities can get surprisingly warm mid summer. Montreal can often get into the high 80's, Quebec City a little cooler. Evenings typically get down in the 60's. Both are great places to be in the summer. Of course by mid September things start to cool off.

Depends on where you are coming from - high 80's in Montreal in summer comes with HIGH humidity. Feels a lot hotter than west coast or desert weather. I like September in Quebec.

We are heading up to Montreal, Quebec City, and Tadoussac in mid-July. We live in Houston, TX where it is already in the mid-90's and pretty humid. If the temperature goes down to the 60's at night it will feel wonderful to me!

We visited Quebec City in late September/early October. I brought sweaters. I SHOULD have packed lighter clothes. It was too warm for fall attire! It was in the mid 80's every day.
I absolutely loved the area! Have a great trip.

Hi Minnehappylis---You did right to pack sweaters; I've ever worn GLOVES in Montreal at the end of September. As one is approaching later September, I'd advise generally speaking having a fall jacket and some sweaters handy, but these things are variable and one CAN hit a warm spell.

Monterey Bob-- To add to this, I've been here in mid-June and the temperature has been 95 degrees F; however the past few days it's been in the low 60s as a high. Generally, that's the game for June, July, August and early September. The sticky, hot stretches we call "les canicules" tend to be pretty short (1-2 weeks), but occasionally vacations happen to hit those stretches.

Cheers, DANIEL