I think you may be!
There is a possible low temperature warning tonight at least.
You could put them out for a while in the day but take them in again, this would begin to harden them off

My sweet peas have been outdoors in a cold frame for the last month...coming along nicely, will most likely plant out first week in May, but have planted out in March in previous years when weather not been so severe.

I agree with Pam start hardening them off by putting them out during the day and back into the greenhouse, or where-ever, overnight for a couple of weeks then check what the weather forecast is saying.

Mine should have been in 3 weeks ago but the cold spell stopped that. Now that the soil has warmed up they are going in today.

mine are doing the greenhouse hokey cokey for at least another week or so.