I took the plastic cover off my greenhouse a long time ago for two reasons:
1) It was getting blasted hot inside the greenhouse, even though I never got around to installing the "ends" on my greenhouse.
2) My plants were running into the 5-foot 2-inch 'roof.'
The garden did great 'topless' all summer, even with me being absent for weeks on end. But Hurricane Irene was set to arrive off my coast around midnight last night. Predictions were rainfall of 2 to 6 inches and winds of 20-60 mph.
I mainly worried about the rain. I didn't want my system to flood and overflow.
Worst case if my system flooded was the water level in my sump would overflow the lip of the sump tank. The goldfish in my sump probably wouldn't even get washed out of the system. Unless I developed a clog in the piping between my fish tank and sump, the fish tank wouldn't overflow. Even with a clog, the cover on the tank will keep the fish inside.
Long term, adding as much as 6 inches of rain water to my tank could throw off the water chemistry. Not sure how much of an impact that would have since the fish and plants are so well balanced and I have no ammonia, no nitrite, and low levels (ppm) of nitrate in the system right now.
Wind could do a number. My growbeds are filled with hydroton, which in itself doesn't anchor the plants well. I do have 2 inches of gravel in the base of each growbed, but I'm pretty sure that won't help against tropical storm winds.
To mitigate both the rain and wind, I loosely covered the greenhouse frame with plastic for the weekend. I harvested basil and moved the banana plant, since they were too tall to fit inside. The banana is now in a large planter in my basement. I blanched the basil and turned it into a quart of pistou (pesto without the pine nuts).
We spent the evening reading, munching on toast with pistou, waiting for the storm to pass. From our digital clocks, it looks like we briefly lost power around 2 am, but that was it. The garden fared well, with just edge flaps of the plastic coming undone. Once things dry up this afternoon, I'll go ahead and remove the plastic again for the rest of the summer.