I'm fuzzy on details but I remember reading it had some pretty crazy thermal expansion. I think the pilot had to wait quite a while (hours?) before opening the cockpit to give the plane time to cool enough.

It's also cool that the whole thing was machined 'loose' so that it would expand as it heated up. Apparently the plane would leak fuel and oil when it was on the ground ...

Yep, JP-7 [1]. Special low vapor pressure to mitigate accidental ignition hazard.

The Sled leaked like a grad student's '69 VW bus in the hangar. Leak-free above > 1.5 Mach.

What does winter mean at 80 000 ft and Mach 3?

The jet stream is insanely fast at that altitude mixing the air, and at Mach 3 the surface weather changes in fractions of a minute.

Winter means that your nearest pole is tilted away from the sun. Your half of the planet is cooler, especially towards the poles.

For instance the James Webb telescope gets clearer pictures in summer because in winter the astronauts breath can fog up the lens.