[ohioboxster]

To answer your original question, no. The humidity will not affect your brake pedal. Lets start with the basics. Lets have year, miles, auto or stick and do you see any fluid on the floor or ground? If your pedal is weak or mushy this most likely means you have air in the line. If you have a leak then you will be low on fluid hence the sucking air into the system and dripping fluid. Pop the hood and check the level first. This will give you a good place to start. Im not saying if its low then all you have to do is add fluid but atleast we will know some basic element of the problem. The 5-speed uses the same reservoir for the clutch as brake system. I ask the year and miles because brake fluid absorbs water. It could something as simple as flushing the system with new fluid. So give me more info and I will try to help. Dont be so quick to just hand money to the dealership unless you are just not a do it yourself kind of person.