Absolute minimum temperature?

[wiggy]

Originally Posted by TopBunk

As an aside, I recall flying over Siberia in winter probably about 15 years ago.

We were in a B744 @ FL370 or so. The SAT outside was pretty much standard ISA at about -56degC, the temperature on the ground at Irkutsk (or wherever) was -57deg C!

Yup, Certainly looking at trop level on the Siberian charts some winters days it was clear you'd have to descend a heck of a long way before you saw the OAT increase. I've certainly seen the SAT rise by a degree or two as a result of a step climb when "up north" .