The weather in Irvine showcases the characteristics of a Mediterranean Climate, influenced more by the coast than inland cities like Fullerton or Anaheim, resulting in generally mild and cool conditions. The average annual temperature is around 62–65°F (approximately 17–18°C), with annual rainfall averaging about 13–14 inches (around 330mm).

Seasonal characteristics reveal that spring (March to May) is the most pleasant season in Irvine. Daytime temperatures range from 65–75°F (18–24°C), making it an ideal time for outdoor activities with beautiful flowers and greenery. However, it coincides with spring pollen allergy season, which can be uncomfortable for allergy sufferers.

Summer (June to September) is the longest dry season in Irvine. Due to coastal influences, temperatures are often lower than in inland cities, with many days maintaining highs of 75–88°F (24–31°C). In June, morning fog and overcast conditions (June Gloom) can make it feel surprisingly cool, almost as if it's not summer. The low humidity allows for a comfortable experience in the shade.

Fall (October to November) is the season with the most weather variability in Irvine. It coincides with the Santa Ana Winds, which can cause sudden spikes in temperature to 90°F+ (32°C+), while returning marine influences can lead to unexpectedly cool days.

The Santa Ana Winds can dry out the air significantly, increasing the risk of wildfires and causing dryness in the skin and respiratory system. Winter (December to February) marks the rainy season in Orange County, with most of the annual rainfall occurring during this time. Nighttime temperatures drop to 45–55°F (7–13°C), with rare instances of falling below 40°F (4°C). Snow is almost nonexistent.

The weather in Irvine may initially feel strange to immigrants from Korea, as they might perceive it as lacking four distinct seasons. However, most Korean residents consider the absence of winter to be one of the greatest advantages of living in Irvine.

Due to strong UV rays, SPF 50+ sunscreen is essential year-round in Irvine, and the low humidity can lead to skin dryness, so it's advisable to pay attention to moisturizing and hydration. Checking real-time air quality in Irvine on AirNow.gov is also essential during wildfire season.