Mexico won’t let you enter if your passport is within six months of expiring, and if you land in Mexico City with such a passport you will almost surely be returned to your country of origin. So check the expiration date on your passport, and if it’s within six months renew that passport now.
It’s important to stay hydrated. Not only can Mexico City get very hot, the city is battling intense air pollution. Drinking water helps keep your respiratory, cardio-vascular and immune systems strong.