I live in Ontario, I have a cover that allows the water to pass right through, so every year I expect the water to be higher than the jets.

It's been very cold this past week with snow. I know I would have an awful hard time removing the cover, draining the water, and re-plugging the drains due to snow and cold.

I know I would not be able to do as good of job plugging the lines in these circumstances than in the relative warmth of the fall so I wouldn't bother.