As far as I know, it only slows at frost temps. It's always flowering. If 50's is your overnight temp you have nothing to worry about. Freezing is death, and if its outdoor there's nothing you can do but pull it. My temps are around 40 at night right now and I still have about 3 weeks left, they're still budding like bastards. Bottom line, if you get frost try to cover them, for bud mold reasons only. The cold will slow growth but not stop it. If you have a freeze, sorry bro, you need to pull. I had to do it 3 weeks early last year, decreasing my yield and quality, it sucked.