Who knew?! Conditions can wary. Maybe you have used brakes more frequently and next day maybe you have splashed some water mixed with fuel on the discs...
Bad brake fluid is bad in all weather conditions. Also for calipers, if you have some drag, you will overheat your brakes sooner and they will be lost regardless of weather conditions (sometimes sooner, sometimes later). If the bad brake fluid is the only reason, you can brake almost fine in the beginning, but later ... you are in trouble.
However, play on safe side and get them checked by someone experienced. You don't need to risk. Check for drag, replace the fluid if it is older than 2 years, let some air out from brake lines, clean the discs... it is not too difficult, but some knowledge is required.