When the temperatures drop or if it is damp outside my horn sounds and I need to remove the fuse to get it to stop what could be the problem

If horn stops with fuse removed, the problem is in the steeringf wheel. If horn continues to sound with fuse removed, the problem is a defective horn relay (located in fuse panel under hood).

• The horn relay might have welded contacts (stuck in the on position). Pulling the relay should stop the horn.
  
• The wiring harness on the steering column might have a broken wire to the horn relay shorting to someplace that applies power to the relay. In this case, turning the steering wheel all the way to one side or the other may stop the horn, and it won't sound when you press the horn button.
• The horn button in the steering wheel is stuck on or shorted.

I have a 1977 Cadillac Seville and it does the same thing, and when the outside temperature drops below 65 degrees the horn will sound continuously until either the horn relay or the horn fuse is removed.

The problem is in the horn pad on the steering wheel, and the contact plates inside of the horn pad are too close together (a manufacturing defect) and when the temperature drops down to a certain degree then the horn pad will contract and cause the metal contact plates inside of the horn pad to touch and make contact, and it is same thing as if you were pushing on the horn pad.

I have also heard of the exact opposite happening and when the temperature gets too hot the horn pad will expand and cause the metal contact plates to touch and make contact and activating the horn.

was it hot outside-heat could deform the steering wheel horn pad and make the horn go off,remove the horn pad and airbag unit(take fuse out for airbag system wait a few mins)then put the fuse that you removed back in place and see if the horn goes off again.

the horn switch is part of the sterering wheel assembly.
it needs yto be changed

Very possibly the horn relay. This is located in the left junction block ( fuse panel) on the left side of dash. Open driver door and you will see a panel cover on the end of dash. On the cover it should list the position of the relay which I believe is on the right of fuse panel. If you try the horn and it sticks on again, try tapping the relay, if stops then that is the problem.

youve got a bad horn relay

I have seen this happen in damp areas and very cold areas where condensation sets in and shorts out the circuit, thus soundig the horn. Good luck and remember to rate all the solutions you get, thanx.

Sounds like you may have corroded terminals on the horn itself.

Find the horn in the engine compartment - remove the wire connected to it - clean the spade terminal with some sand paper and push the terminal back on. If that doesn't work you may need to remove the horn from the car and clean up the earth connection, i.e. where the horn is attached to the body work of the car to get a good electrical contact.