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Santa Ana sits in the heart of Orange County, where a warm Mediterranean climate, coastal marine influence, and dry Santa Ana winds combine to produce a long, active allergy season with relatively few true "off" months.
Tree pollen is the earliest and often most intense trigger, typically ramping up in February and peaking from March through May. Common local offenders include olive, oak, sycamore, mulberry, ash, elm, and the region's many ornamental and non-native pines and junipers.
As trees taper, grass pollen takes over from late April through July, with Bermuda grass, ryegrass, fescue, and Kentucky bluegrass dominating due to their widespread use in lawns, parks, and medians.
Fall brings weed pollen, generally August through November, led by ragweed, sagebrush, pigweed, Russian thistle (tumbleweed), and plantain.
Because Southern California's mild weather can extend growing seasons, tree and grass pollens often overlap in spring, intensifying symptoms for multi-sensitive individuals.
Beyond pollen, Santa Ana residents also contend with year-round dust and dust mites, outdoor mold spores (especially after rain or in irrigated landscaping), and elevated particulate pollution from regional traffic and wildfire smoke.
Overall, Santa Ana's allergy profile is characterized by an extended, overlapping pollen calendar compounded by dryness, wind-driven dust, and urban air quality concerns.