Is it safe to use WD hitch when raining?

Sounds like you have too much weight taken off the rear axle. maybe try taking off a link or 2!

Scale the rig.

I just did mine..
weight distribution hitch..
front wheels .. with trailer the truck front end has 100 pounds less than without trailer

F 250 and a 8,500 pound trailer.... trailer paperwork states 7,500 pounds.
paperwork is Way OFF...
trailer was Empty... except for cloths for 3 days and for 2 people.

as others have stated.... remove or release friction sway control

I went to a CAT scale station at a Pilot J... 10 dollars.
was on my way Home from a weekend camping trip.

Also maybe too MUCH compression on the WDH. Check the weights and maybe back it off. With my 7000lb trailer and the F350 I have the WDH on the minimum number of links. The truck does not need much due to the much heavier axles of the bigger trucks. Maybe get yourself weighed and adjust the hitch.

You're not driving a 1500/150 series truck, you don't need a lot of compression on the hitch with a 2500/250 truck and 7000lb trailer.

I don't know what type of Sway control you are using. however. Sway bar manufacturers suggest you loosen, or remove it in the rain, or other slick condition. They can cause the TV to go straight in a turn.
From the Reese sway control bar instructions

4. When towing during slippery conditions such as wet, icy, or snow-covered roads or on loose gravel, turn on/off handle (5)
counterclockwise until all tension is removed from unit. Failure to do so could prevent tow vehicle and trailer from turning properly.

I wonder if that could be adding to the "wiggle" feel?

Check the tire inflation. And, possibly slow down. 60-65 is about as fast as you really should be running while towing.

As pointed out already, the WD hitch enhances stability in any road condition. Two points to ponder: don't use the cruise control or your exhaust brake on any road that isn't clean or dry.
Randy

Most of the hitch weight still goes on the rear wheels but as said, too much off the front wheels means less steering capability.

coolmom42 wrote:
You definitely need that WD hitch MORE when raining---it serves to put weight back on your front wheels. Without that weight being returned to the front your steering will be very poor and the entire TV will be even more unstable.

If your rear wheels "wiggle" you need to check your tire tread, inflation, and the type of tires.

You should not be feeling "wiggle" at any time and your vehicle should be just as stable on a wet road as a dry road.

thread is pretty good. The tires has about 8000 miles on it as i bought the Ram of April this year only.

You definitely need that WD hitch MORE when raining---it serves to put weight back on your front wheels. Without that weight being returned to the front your steering will be very poor and the entire TV will be even more unstable.

If your rear wheels "wiggle" you need to check your tire tread, inflation, and the type of tires.

You should not be feeling "wiggle" at any time and your vehicle should be just as stable on a wet road as a dry road.