What you pack for your Mexico tour will depend on where you are travelling to. Mexico City, for example, will be much cooler than the coastal areas of Playa del Carmen or Tulum, thanks to its high altitude. In the winter, it can drop down towards freezing at night while reaching 23°C during the day, so it’s important to be prepared for both ends of the spectrum.
From December to April, the country tends to be drier and cooler than the rest of the year. If you’re in Mexico City, Puebla, or any other high-altitude areas, you’ll be okay during the day with a light jumper, jeans, or even shorts, but will most likely need something warmer for the evenings as it can get cold.
On the coasts, even in the winter months, it’s generally warm and balmy, so you can get away with light clothing, though it’s best to pack a light jumper or jacket for the evenings.
During the summer, most of Mexico, excluding the desert regions up north, experiences quite a lot of rain. It’ll be hot and humid, so light clothing should suffice, but be sure to pack a waterproof jacket.
You'll also want to make sure to pack decent footwear and comfortable clothing for inevitable taco crawls.
Read more about the best time to visit Mexico.