I've been reading a book called "Cold: Adventures in the World's Frozen Places " (http://www.amazon.com/Cold-Adventures-Worlds-Frozen-Places/d...):

"One degree of frost was one degree below freezing Fahrenheit. An explorer might write in his journal of fifty degrees of frost - negative eighteen degrees Fahrenheit"

You should read that as -40 degrees - likely Celcius and not Fahrenheit you refer to. Funny thing is, -40 C = -40 F.

I've seen the phrase in a Jack London story. That would be 40 degrees below freezing. For Celsius that would be -40C since freezing is 0C. For Fahrenheit that would be -8F (32 - 40).

Probably means minus 40 degrees. Which incidentally is the same in Celcius and Fahrenheit.

To me that reads as "-40 degrees Celsius" since in Celsius 0 degrees is exactly where water freezes.

I guess they mean -40 °C (coincidently -40 °F) not +40 °F (4.4 °C).

I'm a native Russian speaker, this means -40 Celcius. In Russian, we say "X degrees of frost" (градусов мороза) to refer to temperatures below zero Celcius.

> I don't believe frost forms until 32 degrees.

Perhaps it was under 10 atmospheres of pressure? ;-)

I think they've meant -40 C.