It's Cold In The Desert Too

Wow! Saguaros can't tolerate more than about six hours of sub-freezing temperatures:

Tucson hit a record low Monday morning and another hard-freeze is excepted for Tuesday and Wednesday mornings, according to the National Weather Service.

Monday’s low at the Tucson airport was 21 degrees. That breaks the record low for the date of 22 degrees, set in 1940.