I have re-drained the house and the only thing left is to attach the trim at the top of the moisture barrier mat. From what I've read, you should apply silicone under the trim before nailing it down. Now that it's started to be below freezing and snowing outside, what do I do? Is it okay to still apply the silicone? I mean, what's the worst that can happen, it will still seal anyway 
Tec 7 can be applied in sub-zero temperatures. It seals then but fully cures in positive temperatures. Tec 7 is also supposed to have a longer lifespan than silicone. There are certainly other brands with equivalent performance as well.
I work with assembling doors and gates in cold and freezer rooms, we seal with silicone Sikasil building/sanitary, and even though it says min +5 degrees on the tube, I know for sure that it also works in subzero temperatures.