I would like to see what others say about this but I'll say yes, it probably will help to leave your phal outdoors over night. I grow my phals outdoors in Florida and when the nights get below 55 I start to see spikes. What I don't know is how many nights with low temperatures it will take. The other problem is that you don't want your plants outside if it's going to get into the low 40's. I would also place them in a spot where they won't get any wind. Phals do not like the combination of cold and wind. Good luck.