I was there only once in May, so can't speak about seasonal variations. By "cold air", I don't mean in an absolute sense, but in a relative way. As long as the night is clear and there is no synoptic weather to make it breezy (say an approaching trough kicking up a SW breeze), I would expect the effect would not have a strong seasonal component. If the weather is clear and stable, you're gonna get that katabatic flow every night. \Brian --- This message is from the AZ-Observing mailing list. If you wish to be removed from this list, send E-mail to: AZ-Observing-request@xxxxxxxxxxxxx, with the subject: unsubscribe. The list's archive is at: //www.freelists.org/archives/az-observing This is a discussion list. Please send personal inquiries directly to the message author. In other words, do not use "reply" for personal messages. Thanks.