The term "more sub-zero" refers to a temperature that is even colder than sub-zero. However, when looking for antonyms for this phrase, one might consider words that describe temperatures that are warmer or above freezing. Some possible antonyms for "more sub-zero" include mild, temperate, warm, hot, balmy, and tropical. These words convey the opposite of the coldness associated with sub-zero temperatures. Additionally, words like heat, warmth, sunshine, and humidity might also be considered antonyms, as they suggest conditions in which temperatures are higher and more comfortable. Together, these words offer a range of options for describing conditions that are the opposite of "more sub-zero.