Originally Posted by prathmann

Agree with the first part (although I believe everyone in the thread so far has been using absolute temperatures), but not with the last sentence. The only way having your butt on the seat will raise the pressure is by reducing the tire volume. But the volume is unchanged except in the immediate vicinity of the contact patch which only comprises a few percent of the tire circumference. And even in that few percent the volume change is pretty minor. The volume change (and therefore also the pressure change) from sitting down on the bike will be well under one percent - i.e. insignificant.