Even though the park shares a border with our southern neighbors, the elevation and the mountain ecosystem keeps Coronado National Memorial relatively cool in the summer, and in the winter... snow! (on rare occasion)
Summers are warm, with daytime temperatures in the 90s F (32-37 C) and low humidity in May, June, and July. The summer rainy season (monsoon) is between late June and early September. Monsoon thunderstorms can cause flash floods. Never drive through a section of road that is flooded -- Turn Around, Don't Drown! Precipitation, including snow, averages about 20 inches (51 cm) per year. 2015 precipitation totals reached nearly 26" this year!
Winter temperatures often fall below freezing at night, with highs 40-60 F (4-15 C) in December and January.