I have a 99 250 and when ever it rains the truck wants to shutter when driving and then will cut off sometimes at a light. Was wondering if anyone else ever had this problem and if so what might cause this.

 

Check your CPS connector and dab a little dielectric gease on it after you clean it. Could be the infamous CPS dying but since you are only getting it during weather I would look to the connector first.

Also check the harness where the plastic clip holds it to the engine they have a tendency to come out and the serp belt could chaff the wiring

 

For $55 on ebay just get one for when it goes bad because it will. Just check all the CPS threads listed. I have an 01 that first showed up at idle then while running down the road wet or dry it would cut out. Replaced CPS and it seems to have cleared it up.