Damn, it should snow in England this year...London especially, but it wont
Though if it did, it would be wicked. I'd put Immortal on real loud so I could hear it outside, and then if no one was in, I'd have an air guitar/ headbanging session in the garden.
Also, when it gets really dark, you could light some candles, and stick Darkthrone on...ooohh creepy stuff. I reckon that would be the idea way to listen to Darkthrone!
Then erm..."Emperor - Anthems to the Welkin at Dusk" during a thunderstorm...wow. I think Opethiansoul posted about him listening to "Anthems..." on the balcony during a thunderstorm. That would just be...wow!!!
Ok, what could we have for Mayhem...hmmm...erm...AH HA!!! During a full moon near Halloween stick "De Mysteriis Dom Sathanas" on..."FOLLOW THE FREEZING MOOOOON"!!!!!!....or even better, as near Christmas day as possible
I'll let the rest of you think about when to play Marduk, Burzum, Dark Funeral and, and...all the others that have escaped me for the time being.