How the timing is planned
A dry window is part of scheduling, not an afterthought. We look at the forecast for the days after the visit, not just the day itself, because the cure happens after we leave.
If the window is not there, the visit moves. That is cheaper for everyone than working into rain and coming back.
If rain arrives anyway
Forecasts are forecasts. If rain lands inside the curing window, we return at no charge to deal with it, and you do not need to argue for that: it is part of how the work is done.
All you need to do is tell us when it rained and what the roof looks like afterwards.
What not to do in the meantime
Keep off the roof while it cures, and do not try to wash or wipe the surface. There is nothing to fix by hand in the first two days, and foot traffic on a curing surface is the thing most likely to make it worse.
Inside the house, nothing changes: the roof is still keeping water out while the surface cures.
The rest of the year
Once cured, rain is simply the weather. A treated surface sheds water rather than holding it, which is the point of the application, and there is nothing to reapply between visits.
If water appears inside at any point, that is a report rather than a rain question, and the free inspection is where it starts.
Planning the visit around the forecast
The reason the visit is scheduled rather than dropped in is the cure. Two dry days after the application matter more than the weather on the day itself, so the forecast that decides the booking is the one for the following 48 hours.
That is also why a treatment planned for a settled week is easier than one squeezed in before a storm front. If the window is not there, moving the visit costs nothing; working into it means coming back.
Rain in the forecast after booking
If the forecast changes in the days before the visit, tell us rather than hoping it holds. Moving the visit is simple; treating a roof that will be rained on within hours is not.
And if the application is already done, a wet day is not a crisis: the surface cures over those two dry days, and if rain interrupts them we return.