1st Nov 1970 AC851 DC-8 (-60?) London to Calgary to start my new job in the oil industry. The first time I had flown in a commercial jet at the age of 23. Hard to believe these days.
Calgary was fogged in due to upslope conditions, so my first night in Canada was in Vancouver. I knew Calgary wouldn't be quite the same as Vancouver, but I wasn't quite prepared for the reality of the Prairies in winter!
I had another memorable flight into Heathrow about 10 years ago. We had arrived at Heathrow on a L1011-500 (AC never referred to them as Tristars) about mid-day after leaving Calgary the night before where it was -35. There was a short delay getting the doors open and then the purser announced in an amused tone "There will be a delay in unloading your baggage, because of the extremely low temperatures here at Heathrow" . After a short pause, he said "It's -5!".