"Ed Huntress" fired this volley in
:

I've used a whole tube of
silicone caulk to seal two lights. I loosen the lenses and caulk under
the rim; cover the screws with caulk before driving them in; and seal
the wires inside and out.

One should be careful to use the Silicone-II formula, which releases
methanol upon curing. The acetic acid released from the original formula
can do some pretty nasty damage to electrics.

LLoyd