Weather & Climate

Climate Type:

The climate type in Los Angeles is categorized as Mediterranean. The summers are considered to be dry with significant changes to the rainfall patterns, mostly occurring in the winter. The overall transitions in temperature are quite moderate (1).

Temperature:

Los Angeles typically has hot, dry summers and mild, wet winters. The yearly average temperature ranges from 57 to 72 degrees Fahrenheit and 14 to 22 degrees Celsius. The warmest months are July, August and September and the coldest months are usually December, January and February (2).

The figure above shows the average monthly temperature and precipitation levels for Los Angeles. The blue lines signify the rainfall levels and the red line represents the average temperature (3)

Precipitation:

Los Angeles receives the most rainfall during the time period of November to March. This can be attributed to the Aleutian Low which delivers cool, moist air to the Pacific Ocean towards the surrounding region (5). January and February typically have the highest levels of rainfall with August having the lowest. The average annual precipitation levels typically fall around 14 inches (4).

Humidity:

According to this figure on the average humidity levels for Los Angeles, May is usually the most humid month at 73% and November is the least humid month at 50%. The average percentage of humidity is around 65% (6).

Wind Direction:

The wind direction is typically from the west from February to July and then again from August to October. The direction comes from the south from July to August, and from the north from October to February (7).

Global Wind Patterns:

The main global wind patterns in Los Angeles are trade winds, westerlies and the polar easterlies. The northeast trade winds result in the region's moderate weather. The mid-latitude position of Los Angeles plays a part in the westerlies and the global circulation patterns influence polar easterlies (8).

Air Masses:

The two main air masses include Maritime Tropical Air Masses and Maritime Polar Air Masses

The Maritime Tropical Air Masses come from the subtropical Pacific Ocean and deliver warm and moist conditions. The tropical air masses bring about the hot and dry weather which has the potential to result in drought conditions. For the winter months, the air masses deliver precipitation which contributes to higher rainfall levels than the rest of the year.
The Maritime Polar Air Masses comes from the northern Pacific and brings the colder conditions to Los Angeles. This air mass leads to more precipitation in the winter, as well as cooler temperatures. The polar air masses also bring more variability of weather especially in the winter months (9).

Weather Systems:

Some of the weather systems in Los Angeles include: Pacific Storms (11), Santa Ana Winds (12), Drought Conditions (13), and Earthquakes (14). Pacific Storms typically occur from December to March and are driven by westerlies. The Santa Ana winds occur from October to April and typically come from the high deserts and wind systems over the Great Basin. The drought conditions can be prevalent throughout the year and are the result of the hot and dry weather. For Earthquakes, this also occurs throughout the year and having Los Angeles centered near the Pacific Ring of Fire which causes seismic activity.

Climate Type and Characteristics:

The Mediterranean climate is often categorized as "dry-summer subtropical" weather. This means that the summers are often hot and dry, and the winters are often mild and wet.

Works Cited: