steamboat might be, i remember going at the end of september a few years back, it was pretty cold in the lake, haha. if you have a wetsuit or one you can borrow the BRING it cause being outdoors that time of the year soaking wet can be unpleasant with unpredictable weather...there's also woodward at copper, but those jumps into the foam pit are smaller than water ramps.
PC closes on like the 15th of September. And Im pretty sure thats when the pool closes. It might be open for another week after that but its for the US team only.
the only ramps I know that are open later is the ones in Quebeq City.