extra moisture during the wet months moderates the temperatures, resulting in cooler days and nights during this period. The highest temperatures are usually reached in May averaging , but can reach up to just before the onset of monsoon season. March tends to be the driest month and July the wettest, with an average of of rain, over a quarter of the annual average of about . During the summer, afternoon storms are very common and can sometimes bring hail flurries to the city, especially toward late August or September. Winters are relatively warm despite the city's altitude, with January daytime temperatures reaching about and nighttime temperatures about . However, the outskirts of the city (generally those close to the Primavera Forest) experience on average cooler temperatures than the city itself. There, temperatures around can be recorded during the coldest nights. Frost may also occur during the coldest nights, but temperatures rarely fall below in the city, making it an uncommon phenomenon. Cold fronts in winter can sometimes bring light rain to the city for several days in a row. Snowfall is extraordinarily rare, with the last recorded one occurring in December 1997, which was the first time in 116 years, as it had previously last fallen in 1881. Topography Guadalajara's natural wealth is represented by the La Primavera Forest, Los Colomos, and the Barranca de Huentitán. The flora in these areas includes michoacan pines, several species of oak, sweetgum, ash, willow, and introduced trees such as poincianas, jacarandas, and ficus. It also includes orchids, roses, and various species of fungi. The fauna includes typical urban fauna in addition to 106 species of mammals, 19 species of reptiles, and six species of fish. La Barranca de Huentitán (the Huentitán Forest) (also known as Barranca de Oblatos and Barranca de Oblatos-Huentitán) is a National Park located just north of the municipality of Guadalajara. The barranca (canyon) borders two colonias (neighborhoods) of the city, Oblatos and Huentitan. It covers approximately , and varies in altitude. The funicular railway in the park starts at above sea level and rises to above sea level. In the 16th century, during the Spanish Conquest, the Huentitán area including the canyon was the site of battles between local Indian populations and the Spanish. Later, it was the site of battles between different factions during the Mexican Revolution and the Cristero Rebellion. The canyon is a biogeographic corridor