While Midwest has enjoyed unseasonably warm days on Wednesday and Thursday /https://mkweather.com/2020/11/20/last-warm-days-in-midwest-north-platte-233c-73-9f-chicago-189c-66f/; https://mkweather.com/2020/11/17/after-arctic-blast-in-eastern-usa-short-indian-summer-for-midwest//, in southern USA was even more extremely hot.
Phoenix on Wednesday, 18. November has experienced with extremely hot, tropical day, with maximum temperature 92°F / +33,3°C!
In late autumn, never has been so hot so late according to historic measures since 19. century.
On the maps of temperature in 850 hPa we should notice, that extremely hot air has flown from the south and continued with direction towards Great Lakes from Wednesday to Thursday, 18.-19. November 2020.
Above Phoenix has appeared air masses with temperature in 850 hPa above +20°C, what is very untraditionally for the second half of November.
In 2020, Phoenix has experienced with record number of days above 110°F (34 days) and above 100°F (143 days) in all-time history.
Extremely hot weather during the autumn 2020 is result of persisting La-nina pattern, which is linked with dry and hot weather above southern parts of United States.