Definitely a fluke, lol. IIRC, the finale was actually filmed in the middle of fall like in October or so (you can see some orange trees in the background from time to time), so yeah, I imagine it may have been chilly when filming the finale. Of course, the cast has talked about the drastic change in temperatures filming out there on a daily basis, ranging from the teens early in the morning, soaring to well over 100 in the afternoon; Alan Alda has said how he and Wayne Rogers were freezing in their Hawaiian shirts filming the opening sequence for the pilot where they're playing golf on the helipad, meanwhile I remember Loretta Swit talking about an incident where an extra or crew member nearly died from heat stroke.