Fermenting Under Vacuum?

So I started a cider a few weeks ago. There was a lot of fermenting and bubbling going on in the first few days; everything looked fine. After about a week, the weather started going from extreme hot to extreme cold and I just found that my fermenter is under a pretty heavy vacuum. The three piece air-lock was pulled on enough to where it's now sealed. If i move the middle piece the rum I have in the air-lock shoots into the fermenter. Is it a bad thing to just leave it like this for a few more weeks? Also, anyone know what caused it? You think it may have been the temperature swings?

It was the temperature swings. As wort cools it condenses and nature looks for a way to compensate the pressures. This is why many people use distilled spirits rather than sanitizer or plain old water.