Hello @William319
Have you considered asking your guests if they would like to come back & stay another time when the fires have settled down?
If they are otherwise happy to be there & they have been good guests have that conversation, you never know the spinoffs who they may share stories with to encourage others to come stay at your home bc of good old fashioned caring hospitality.
You can then do an "Alteration" to your reservation & calendar & neither party loses service fees.
It's easy enough to block off dates for when they decide to come back & do a zero pricing for them.
There's also a wealth of information here in CC about how others have addressed similar issues if you use related words in the search box.
Always remember, "Good Faith & Good Will" for a good working relationship.
Across the miles in Auckland we had yellow, orange & red tinged skies earlier this year and throughout history as a result of the fires in Australia.
The landscape will change where the fires have been, new shoots will regenerate and coal may appear in years to come.
Take some photos and pop them in your listing as a reminder and talking point with guests.
All the best.