CLIMATE

CDMX is at high altitude (7,350 ft / 2,240 meters above sea level), in a valley surrounded by mountains. The highway pass southwest to Cuernavaca, Taxco and Acapulco is at ~10,000 feet, and the nearest large (and recently active) volcano is Popocatépetl (17,802 ft / 5,426 m, snow capped though its glaciers melted in 2001)

Winters very rarely see snow, but occasional freezing nights (I’ve experienced both, regardless of the yearly average climate charts). May is the hottest month with temperatures up to highs in the 80s F / mid-20s C. The rains begin ~May, ending in October. Entire days are rarely rainy, but rain or showers are common overnight and late afternoons. July and August are cooler than May due to these rains.

Atmospheric pollution can be a problem for those with challenged respiratory systems, particularly during the dry season. As well, volcano Popocatépetl is erupting with greater frequency, and though it’s 73 miles / 117 km from CDMX, ash can be present downwind, including sectors of CDMX.

Water is often in short supply, as it was in the days of the Aztecs - who had great aqueducts bringing in pure water supplies. Top hotels provide bottled water in the room, and some have installed filtration systems. The latter may or may not be properly maintained.

Do not drink untreated water or consume impure ice. The city water supply experiences cross contamination due to the ever-settling lacustrine bed environment, and its not impossible to get traveler’s diarrhea or even E, histolytica or Giardia lamblia from tap water. Stick to “electropura” or bottled water (served in most tourist grade restaurants and hotels, even for brushing your teeth. Homes in Mexico tend to offer purified bottled or boiled water or use filtration systems that may not have scientific basis or are not properly maintained or just plain dodgy. Unfortunately, my family use dodgy unproven filtration, so I drink water they’ve boiled when I visit.

Earthquakes rarely happen, but they do occur. Read the earthquake instructions in your room. Though building regulations have improved over the years, earthquakes and aftershocks can be scary, and they can disrupt electrical, communication, transportation and water systems.

Recent major earthquakes (seismic movements in other states are often felt in CDMX, but these are the really significant earthquakes affecting CDMX):

1957 - Richter 7.9 (my first significant quake)
1985 - Richter 8.0
2017 - Richter 7.0

Layers are good, as temperatures can vary significantly between mid-day and evening. You won’t see too many sandals or shorts in the city, and good walking shoes will probably be useful.

Climate chart from www.climate-charts.com.