90 degrees is enough to cook any plant. So I will assume thisis the reason. I do not, however, know of any place that that gets this hot. I think there is a mistake here.
I live in the east coast united states and it has been well over 90 degrees Fareinheight for most of the summer. I'm sure you're thinking in terms of celsius, as you are right, that would be astronomically warm. Odds are OP is from the States.