Hee Hee... well.. August and small parts of September are about the only months with 70ish temps. The rest of the year, it's "more chillier!"

If diving in the River (St. Lawrence), there is no thermocline. But if diving in Kingston or Tobermory, for example, there are thermoclines that are in the 40s quite often, so drysuit = goooooooood.