September in Big Bear Lake, California, typically marks a transition from summer to autumn. This period often experiences warm, sunny days gradually giving way to cooler nights. Average high temperatures can range from the mid-70s Fahrenheit (low 20s Celsius) at the start of the month to the mid-60s Fahrenheit (high teens Celsius) by the end. Correspondingly, average lows shift from the mid-40s Fahrenheit (around 7 degrees Celsius) to the upper 30s Fahrenheit (around 3-4 degrees Celsius). Rainfall is generally minimal in September, making it a desirable time for outdoor activities.
Pleasant daytime temperatures combined with less crowded conditions compared to the peak summer months make September an attractive period to visit the Big Bear area. This shoulder season provides ideal conditions for hiking, mountain biking, and watersports. The clear skies and comfortable temperatures also create excellent opportunities for enjoying the fall foliage as it begins to change color, particularly at higher elevations. Historically, September has been a period favored by locals and those seeking a quieter mountain experience.