As long as there is no wind,they should be okay.I don't know how you feed or when you feed but during the cold wintertime,I make it a very strict point to feed and water an hour before dark.My reasons for doing this is because if you observe peas when it gets colder,they do not drink 25% of the water they do when it's summertime and hot.
If you fill waterbowls in the cold morning,the water will be frozen in an hour and most of the time,peas are not thirsty on a cold morning..I spend a lot,and I mean a LOT of time standing outside of my pens watching my peas in the summertime,and one thing I've learned is if peas are hungry they will eat immediatedly.They will drink as soon as they are finished eating.They are always thirsty after eating dry feed so when I get home from work,I fill the feed bowls first,then get water and give them when they are done eating.
This is one great way to worm your peas with Safeguard.Since it settles out after an hour or so,I mix up 8cc's in 2 1/2 galons of water. I then get one large water bowl and pour some in and let them all drink. Then I take the same water bowl,to the next pen,and keep doing this,and adding the mixed Safeguard drinking water,if the water bowl gets low from one pen to the next.
If the peas are full of feed in the evening,the protein levels helps them keep body temperatures up. At least when it's the coldest my peas are full of feed.And the way I worm mine cuts down on wasting Safeguard. I will water them this way two nites in a row,then again 10 days later for two nites and I'm done.I also make sure if the temps are above freezing,they do not have access to water until I get home,when I know they willl drink during these 4 worming days,insuring they are thirsty.