Humidity in Los Angeles, California Today

Los Angeles has a Mediterranean, semi-arid climate held in check by the cool California Current running down the Pacific coast. That cold offshore water is the key to the city's whole humidity story: it chills the air just above the ocean into a shallow, moist marine layer that drifts inland overnight. Coastal neighborhoods wake up to gray skies and high morning humidity — the famous "May Gray" and "June Gloom" — that usually burns off by midday as the sun mixes the layer out.

Despite that fog, LA is not a genuinely humid city the way the Gulf Coast is. Actual dew points stay moderate, and the mugginess is skin-deep and short-lived. Head inland to the San Fernando or San Gabriel Valleys and the marine influence fades fast: those basins run hotter and markedly drier, so a beach reading in Santa Monica and a valley reading in Van Nuys taken at the same hour can look like two different climates.

Autumn brings the opposite extreme. When high pressure builds over the Great Basin, hot, dry Santa Ana winds rush offshore from the desert and can crash relative humidity into the single digits, priming the region for wildfire. Rain is scarce from May through October, so outside the morning marine layer, most of the LA year leans dry — which is exactly why the coast-versus-inland and morning-versus-afternoon gap matters more here than the daily citywide number.