The sycamore trees still hold their orange leaves. There is ice in small puddles. The manzanitas are blooming. Three seasons - fall, winter, and spring - can be seen on one day in one local area. That is one of the wonders of January in southern California.
Fall tapers off slowly. Here and there, trees like sycamore, willow, and ash may hold their colored leaves into January. Look for them in residential areas anywhere and in coastal-facing canyons. Weather-wise, the Santa Ana winds characteristic of fall can appear in January.
January is a winter month. Most deciduous trees are dormant now. Though there will not be snow at lower elevations, look to the higher mountains for the beautiful sight of snowy peaks. On mornings following clear, cool, and humid nights, look for frost on roofs and grass. (If the air temperature stays above the dew point, there will be no frost.) In colder canyons and low spots, you might find ice on puddles or along slow-moving streams.
January is also a rainy-season month. Although the amount of rain has not been great so far this year, the wild grasses and other annuals are starting to grow. Wildflowers are even starting to bloom. Two of the earliest things to bloom are chaparral currant (Ribes malvaceum) and bigberry manzanita (Arctostaphylos glauca). Both are shrubs of the chaparral.
Some people say that southern California has "no seasons". The observer of nature will see that that is not true. There are several distinct seasons and sometimes three can be seen on one day.