Annual flowers don't set fruit, so night temperatures are less important. Instead, success with these plants is regulated more often by soil and air temperatures. Flowers that should be planted now in our still-cool soil include petunias, pansies and violas, bacopa, nemesia, snapdragons, alyssum, stock, primrose, ageratum, cosmos and most poppies. Don't bother with impatiens, begonias, verbenas, coleus, zinnias, dahlias, marigolds and other warm weather plants; they'll just languish now. Wait until the soil warms and the days lengthen.
Gladiolus, tuberous begonias, dahlias, most lilies and other summer flowering plants grown from bulb-like structures should get into the ground this month or next. The cool air and mild soil temperatures are perfect for their initiation of roots, followed by foliage and flowers.
If we resign ourselves and our gardens to the rules of Mother Nature, then in February we will be planting cilantro, not basil, ceanothus, not bougainvillea, fescue, not bermuda, potatoes, not plumeria, and apricots instead of avocadoes. Those are Mother Nature's desires. Best that we learn her rules, then do our best to abide by them. Mother Nature tells us that it's time to start feeding citrus now. Citrus are heavy users of nitrogen and micronutrients. Micronutrients, like iron, zinc and manganese, are often absent from synthetic fertilizers; another reason why I always recommend organic nutrition. While you're at it, be sure to apply fertilizer to most potted plants. The soil of potted plants will warm considerably earlier than that of the ground, requiring more frequent and earlier applications of nutrition, and resulting in an earlier season of foliage and flowers.