This appears in MacArthur Genius Award performance poet Guillermo Gomez-Pena's book The New World Border: Prophecies, poems & Loqueras for the End of the Century (City Lights Books) coined in Chicago in the 1990's to mean cold weather or "polar" Mexicans. Mexkimo settlements are found in Iowa, Minnesota, Illinois, and British Columbia and Quebec. Mexican or Chicanos who reside decades in the far north can't stand hot weather after living in the northern states of the USA and Canada.
No way can I stand the San Antonio heat after 25 years as a Mexkimo en Chicago.
This cool summer is perfect Mexkimo weather, carnal.