Your brakes do not perform the same in every condition. Weather changes both how the brakes themselves behave and how well the tires can use them. Here is how weather affects braking.
Rain and wet roads
Wet rotors make the first stop feel slightly weak until the pads wipe them dry; see wet braking. More importantly, wet roads cut tire grip, so stopping distances grow even with perfect brakes.
Snow and ice
On snow and ice, grip is the limiting factor, not the brakes - ABS helps prevent lock-up, but stopping distances are dramatically longer; see winter brake care. Salt also corrodes brake components over a winter.
Heat
Hot weather starts the brakes closer to their limit and stresses the fluid, raising fade risk on long descents or when towing; see why brakes get hot and brake fade. Fresh fluid resists heat fade best.
Adjust your driving
In any adverse weather, slow down and leave extra distance - remember stopping distance climbs fast with speed; see stopping distance by speed. Keep brakes and tires healthy so they deliver their best in every condition. Fit quality pads and hardware.