Have some shelter. Another structure they can see your front door from, maybe another business place?
We have a backyard portion of the tour but they only Have to be exposed to the weather for about ten feet if needed. Otherwise I opened a veiwing window availble to the customers at the end of the tour, right next to the exit so they can see what they maybe had to miss in the backyard if the weather was terrible..or if it snowed in the backyard...I'm open almost every night of the entire year.
I got SO tired of shoveling out a maze a few times, then nobody showed up, now I just open the veiwing window...sometimes "Older" = "Smarter"
It only took me...20? years to figure this out?
Cut a hole in the wall! let them see what they missed!