Books are not going to be as rapidly affected as you think, if they are all on a shelf together. They are literally blocks of wood, and even humidity needs a while to work its way into the center of the book. Especially when other books are helping to keep the books shut under slight pressure.
Rapid humidity changes to a lone book sitting out by itself may cause covers to bow quickly. But they’ll go back to normal when the humidity does too.
The temperature itself is no big deal
If you had extended humidity AND high temperatures for weeks and weeks, then you’d need to do something
I know a guy whose rare book storage unit is 90°f plus all winter because the steam pipes for other units pass through his space.
Do you mean 86 Fahrenheit? That would be about 30 Celsius. (86C is roughly 187F)
Don't worry too much about temperature (yet). Focus on avoiding rapid changes in humidity.
Morty