When wet or cold the brakes grab and grind?

Hello,

This could be due to worn brake pads. It is possible due to moisture in-between the pad and rotor creates the noise since the components are worn.

Replacing the brake pads and resurfacing the rotors (if the rotors are within in specifications), should take care of this issue.
If the rotors are below specifications, they will need to be replaced.

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.