Nogales sits on a relatively high mountain pass with an elevation of 3,865 foot. According to the United States Census Bureau, the city has a total area of 20.8 square miles (54 km2), all of it land. Nogales is 5 miles long and 4.15 miles wide.
Nogales has a semi-arid climate, which is less hot and more rainy than a typical arid climate classification such as Phoenix. In the winter months, Nogales averages in the mid to upper 60s, with both January and February averaging daily highs of 64 °F (18 °C). Lows typically settle just below the freezing mark (32 °F/0 °C) on a majority of nights, but it is not uncommon to see temperatures tumble below 25 °F (-4 °C) on some winter nights.
In the summer months, highs average between 90 °F (32 °C) and 100 °F (38 °C), with the month of June being the hottest with an average daytime high of 96 °F (36 °C). Nighttime lows for the summer months remain in the upper 50s and lower 60s for the duration of the season.
The Arizona Monsoon generally runs through July and August, and these months typically see eight inches or more of combined rainfall, which brings the average annual precipitation for Nogales to about 19 in (483 mm). Some monsoon season storms are capable of producing several inches of rain in a short amount of time, creating flash flood hazards.