I replaced a GFCI in the bathroom last year (GFCI is for 3 bathrooms) it kept tripping and occurred after we had weeks of wet weather. After I replaced the new one tripped, not immediately but after wet weather. For the past 6 months no problem. This week lots of rain, it tripped won't reset. Any ideas?

You need to start looking for leaks that may be wetting your wiring or breaker panel.

GFCIs are very susceptible to water contact. You must be getting water into or onto the GFCI.

If the Hot or neutral has any resistance to ground it will trip. Hot and neutral need to draw the same amount of current.
If there is nothing on the load side, it is likely the GFI itself getting wet, like ma064 mentions.
If something is on the load side, that wiring may have a slight contact with ground.
If something on the load side, did you try with the load wiring removed?

Look out side the house for receptacles that are on the same circuit as the bath GFI. Moisture in a exterior receptacle that is protected by the bath GFI will trip the GFI.