Barn wedding at the end of September

I think it's totally fine! Is there no heater in the venue?

View Quoted Comment No! But tons of room for us to put heaters in. It’s a definite “barn” though so the walls aren’t totally solid. The person who owns the barn just recommended that we reconsider our date but the date is pretty much locked in! I thought it would be totally fine but now I’m questioning it haha

View Quoted Comment

Hmmm I would only be wary because even the owner is unsure of the idea. If you're set on the idea though, just tell guests to dress warm and that blankets will be provided!

Strange question, but you're not in the US, correct?
Because if you're saying 18-22 degrees F, I would say omg that's insane. Everyone needs a parka, long johns and boots

18-22 degrees celcius, people should be find with a sweater.

View Quoted Comment Oops - should have made that more clear! I meant Celsius.

I figure with blankets, heaters, dancing and a group of 80 people in a barn, it won’t be too bad but now I’m questioning everything haha

View Quoted Comment Haha. No worries! We're the odd ones here.
But I think you'll be fine with those temps and that number of people!

I think it depends on what time your wedding is. If it is during the day when the sun is still up, it is manageable with heaters. However, if your wedding and/or reception is later in the day after the sun goes down, then this will be too cold. The temps will be a lot colder once the sun goes down.

I got married in December in Sonoma and the temps were in the mid-60s (comparable to your temps). During the day, it was pleasant with wraps/jackets, etc. But once the sun went down, it was too chilly to be outside for very long. We had our cocktail hour outdoors but had heat lamps and a fire pit and blankets. Everything else was indoors. If your event is in the evening and you are not able to have a fully heated room, then I would listen to the barn owner. That is very telling that even the owner is questioning your idea.

I think with heaters you will be fine but don't over do it because body heat is a factor. Hell my wedding is in October in Pennsylvania. It could very well be those same degrees. The ceremony is outside, reception inside. I almost bet with the amount of body heat inside they'd still have the air on actually for us. Ensure guests dress appropriately if you have an outdoor ceremony. They will probably need jackets.