I find that freezing rain is a temp killer but otherwise just have at 'er!
I experimented last year and found that a 4x4 piece of cardboard (with exhaust hole) put over my drum caused about a 10 degree increase in grate temp. So I went to HD and bought that silver insulation and made a coat for my barrel. Depending on the weather it runs about 25 degrees hotter. I've smoked at 350 degrees and no effect on my coat!