What is the source of BB area creaking associated with ambient temperature changes? A general answer would be welcome, maybe encompassing -10C-40C/15-100F temperatures, but my particular ride is an aluminium frame with pressfit BB30 and Tiagra commponents, in Scotland's climate, stored outside but in a shed. Last year I had a tiny bit of creaking/snapping from the bottom bracket/cranks, or at least it was at the same part of the pedal stroke each time. Through the winter when the temperature was generally 5-10C/40-50F it was pretty much silent, and this weekend it's started making a lot of noise again after the temperature ranged from about 0-15C/32-60F in the space of a few days. There's not really anything else I can attribute the change to, I'm assuming there's a small amount of expansion/contraction in the metal parts which may not be uniform across each component - last weekend no noise, this weekend Creak-Clunk City.

Pressfit BBs are prone to creaking at the best of times. When cold, steel inside aluminium will be tighter than when warm, as the thermal expansion of aluminium is about twice that of steel. The difference is only about 0.001% per degree C, but on something the size of a BB from a cold day to a warm one that's around 0.1mm, easily the difference between a tight fit and one with some movement.