I'm frankly not sure what you mean by midwinter festival, but even if I were, i'm not intimately familiar with all the specific festivals: I've said this before, but mythology and religion is one of my weaker areas: What got me into Mesoamerican history was the architecture in The Road to El Dorado, and then reading about Tenochtitlan, so urbanism, archecture, art motis, etc has always been my primary area of intrest.
Obviously over time I've expanded into geopolitics, general society, history, warfare, and yes, religion, but religion is still probably my weakest area, since Mesoamerican religion is legimtately just really complicated since there's a lot of contradictory information from the small amount of sources left, and since the way I've educated myself has primarily been speaking with researchers and other hobbyists as well as reading archeological studies and papers, which tend to focus on more concrete information rather then abstract cosmological stuff and associations.
For example, me and another person had a whole like 4 page exchange earlier today about the specific associations of Tecciztecatl vs Meztli and their iconographic depictions, if they were male or female, if they were the same god or not, and how like every other source and codex says something different.
That being said, it should be pretty easy for you to check, I believe Wikipedia has a list of notable Mexica festivals. Obviously wikipedia isn't 100% reliable but "if it exists or not" should be checakable.>>119855427
Hopefully I don't annoy you there or here, If I ever am, feel free to let me know.