When it's really cold I usually lower myself really slowly onto it. I've tried doing it fast but the moment my cheek impacts the cold rim I flinch a bit and go back up,
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I go outside, kill a squirrel, chop it in half and then smear it all over the seat. The blood warms up the seat nicely. Then I do my business and clean up to avoid the next user being greeted by a squirrely mess.