taillights

When I turn the lights on in my 94 c1500 truck the taillights and panel lights delay a couple of seconds before coming on. The headlights come on right away. I didn't think it was the fuse, since they eventually came on, but checked it anyway (it wasn't the fuse). It seems like it takes longer for the lights to come on the colder it gets outside. Any thoughts and insights would be greatly appreciated. Thanks.