What happens if it rains
One of the problems of decades of experience is that sometimes you lose perspective. It can become much more difficult to understand someones else’s perspective when they ask a question. I have noticed over the past few years sometimes when I am asked “what happens if it rains?” it confuses me. Believe it or not it, it may take a few seconds for me to realize they know millions of water drops may free fall from the sky. They are probably questioning the service.
I find this confusing because rain is an every day experience and for some parts of the country and world it really is an every day event. This fact makes rain performance an early requirement for any new/existing ingredient and product. Since I have known this for 39 years sometimes I presume everyone else does as well.
No material should be applied in the POURING RAIN. The EPA takes the safety perspective in stating this on labels, it uses language like Do not allow to enter storm drains, stream, lakes, and the such. The business perspective would be the waste of money on labor spent driving to the account and applying as well as the cost of material used only to go back out to do it again. This is literally throwing money down the drain.
Each product formulation has a directive regarding rain. If the product has limits below pouring rain the label will so state.
The most direct answer is that once the material has dried (usually in just a few minutes) then the product will perform as expected.