isocrymal

from The Century Dictionary.

• noun A line, imaginary or drawn upon a map or chart of any region, connecting points at which the temperature is the same during some specified coldest portion of the year.
• noun In hydrogeology, a line joining places where the mean minimum temperatures of the ocean water are the same.
• Having equal degrees of cold or equal low temperatures at any time or under any condition; having equal freezing temperatures.
• Having similar physical properties at specific low temperatures.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Phys. Geog.) Pertaining to, having the nature of, or illustrating, an isocryme

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Relating to isocrymes.