Twice every year in Ajijic, on July 23 and May 22,* el sol is directly overhead at solar noon, which today was at 1:59pm local time. That means your shadow is directly below you, not at an angle like it is year round in the Continental United States (or anywhere else north of the Tropic of Cancer or south of the Tropic of Capricorn).
That also means more direct UV rays. And with an elevation of over 5,000 ft (over 1,500 meters), there is less atmosphere in Ajijic to block UV rays than at sea level. At this elevation, UV rays can be as much as 50% more intense than at sea level. That means put on sunscreen and a hat—or better yet, stay out of the sun altogether.
In this picture, Z is leaning her head and shoulders forward to look at her shadow, which is directly below her.
*Ajijic is at a latitude of about 20.25°. Here’s a graphic showing different dates and latitudes where the sun is directly overhead. So while I haven’t done the math, this date is a pretty close guesstimate.