Los Angeles does not strictly adhere to the traditional idea of four distinct seasons defined by the calendar. The Mediterranean climate means seasonal changes are dictated by shifts in temperature and precipitation patterns. Spring begins when the region transitions from its brief, wet winter period into its long, dry summer. Understanding the actual start of spring requires focusing on the consistency of the weather rather than the astronomical calendar.
When Spring Weather Actually Starts
The official astronomical start of spring, marked by the vernal equinox, typically falls between March 19th and March 21st. However, the shift to true spring weather in Los Angeles often occurs earlier. Climatological spring begins when the consistent pattern of winter storms and cooler temperatures gives way to milder, drier conditions, marking the end of the wet season (November through April).
This transition usually solidifies around the middle of March, moving Los Angeles into a period defined by sunny days and reduced rainfall. The experience of spring varies dramatically across the Los Angeles area due to complex microclimates. Coastal regions, like Santa Monica and Long Beach, remain cooler due to the Pacific Ocean’s influence. Inland valleys, such as the San Fernando Valley, warm up much faster.
The temperature difference between these areas can vary by as much as 36°F on a single day. This geographical variation means that spring may arrive weeks earlier for residents living miles from the coast than for those along the ocean. The arrival of spring is therefore more about a localized, noticeable shift in weather consistency than a single date.
Average Temperatures and Rainfall
The core months of spring (March, April, and May) show a clear progression away from the cooler, wetter winter. Average high temperatures in the Los Angeles basin during March range from 68°F to 70°F, with overnight lows around 52°F to 53°F. March still sees the highest precipitation of the spring period, averaging 2.09 to 2.73 inches.
As spring advances into April, the average daytime high temperature climbs slightly, reaching 70°F to 73°F, while lows hover near 54°F to 55°F. The region exits its rainy season in April, with average precipitation dropping sharply to less than an inch (around 0.69 to 0.77 inches). This reduction in rainfall strongly indicates the seasonal change.
By May, the pattern of warm, dry weather is well-established. Average highs maintain the 70°F to 73°F range, and lows settle around 56°F. Precipitation becomes negligible, averaging only 0.35 to 0.42 inches for the month, setting the stage for the nearly rainless summer. In inland areas, temperatures can be 10 to 20 degrees warmer than the coast due to the absence of the ocean’s moderating effect.
Defining Local Climate Phenomena
Late spring in coastal Los Angeles is frequently characterized by the marine layer. This phenomenon is a layer of cool, moist air from the Pacific Ocean trapped near the surface by a temperature inversion (a layer of warmer air above it). The marine layer results in persistent low-altitude stratus clouds and fog near the coast.
This cloud cover is colloquially known as “May Gray” and “June Gloom.” While most common in May and June, the pattern can sometimes appear as early as April. These clouds typically burn off by the late morning or early afternoon as the sun heats the ground, but they can occasionally persist all day, especially on the coastline. Early in the spring season, Los Angeles may also experience Santa Ana winds. These hot, dry winds originate from high-pressure desert regions and can significantly raise temperatures.