Climate of San Diego - Santa Anas

Santa Anas

The months of September through February bring warm winds from the desert that are called, "Santa Anas". Occurring about 10 days out of the year, these winds bring sometimes hot, but always dry conditions. Inland, and in mountain passes and canyons, they can burst out in gusts of 100 miles per hour (160 km/h) and can lower relative humidity to single digits, although by the coast they rarely see gusts of over 40 miles per hour (64 km/h). They can spread and worsen wildfires. Because these winds blow from east to west, common perception is that they are pulling hot air from the desert. However, it is not uncommon during a Santa Ana condition for the coast to be even hotter than the desert regions. The Santa Ana winds are actually warm due to barometric pressure increases: as the air is pulled down to sea level from the higher altitudes of the Great Basin and Rocky Mountains to the east it compresses and heats up.