Why do my brakes grab when it rains?

My 98 ford f150 has started doing something weird. If it was rained or just moist outside my brakes grab. I press the pedal and the grab real hard and makes a metal on metal noise. The pads are fine. If i power brake it for a minute it stops. It only does this like i said when it's moist out. To be clear its not from running through water. I'll go out start my truck and it does this only when i first get in or when it has sat for a couple of hours. Doesn't do it if i'm driving and they get wet. Like i said it's weird. Any Ideas?

My 98 ford f150 has started doing something weird. If it was rained or just moist outside my brakes grab. I press the pedal and the grab real hard and makes a metal on metal noise. The pads are fine. If i power brake it for a minute it stops. It only does this like i said when it's moist out. To be clear its not from running through water. I'll go out start my truck and it does this only when i first get in or when it has sat for a couple of hours. Doesn't do it if i'm driving and they get wet. Like i said it's weird. Any Ideas? I just cleared this problem up with a Toyota Corolla. The culprit was the rear brake drums
had a lot of brake dust in them. Cleaned them up and the problem is gone. This may be the
case with your front rotors or rear drums. Drums are more likely to experience this problem as
the dust collects in them and stays in them much easier than rotors.

Good Luck You have bad calipers. I had my engage and heat the wheel so much it turned the colour of the metal from silver to gold and I could smell the tire from the heat. I had to replace the caliper along with the bearing and repack the grease. By the way… It was on a Ford F 150 XLT Lariat Edition. A lot of cheaper pads grab when they're wet. Hi so time to get it looked at. You don't brake hard enough when stopping. A glaze builds up on the rotors if you always slow down gently or coast up to a stop sign. Go out and do several "emergency stops". From 60 mph down to 20 mph to try and burn the glaze off of the rotors and see if that helps in the future. Look at your rotors to see if you have any blue hard spots from cheap brake pads.

You have bad calipers. I had my engage and heat the wheel so much it turned the colour of the metal from silver to gold and I could smell the tire from the heat. I had to replace the caliper along with the bearing and repack the grease. By the way… It was on a Ford F 150 XLT Lariat Edition.

A lot of cheaper pads grab when they're wet.

Hi so time to get it looked at.

You don't brake hard enough when stopping. A glaze builds up on the rotors if you always slow down gently or coast up to a stop sign. Go out and do several "emergency stops". From 60 mph down to 20 mph to try and burn the glaze off of the rotors and see if that helps in the future. Look at your rotors to see if you have any blue hard spots from cheap brake pads.