How will seasonal allergies present in my cat?

Seasonal allergies are typically seasonal. I know that sounds pretty obvious, but when somebody brings a kitty to me, one of the first things I want to find out is how long the problem has been going on and has this problem occurred in the past? Is there a pattern to it? Is there a particular seasonal pattern year over year? Maybe it's the first time it's shown up, but maybe it's the fourth or fifth time. If we can see a pattern to when it develops, whether in the spring or summer or a combination of those seasons, that is extremely valuable information to help us better understand the seasonality of an allergy.