Anyone who has tried to bring color to container gardens or landscape with newly purchased flowers during that drab green steambath has watched them cook, then wither away.
Color sells, and many annuals are grown to tantalizing perfection during winter's cooler months.
Buy them and plant them in the spring, and their days are numbered. November and December are good times to plant the pansies and petunias and snapdragons and alsyssums and stocks you see in full bloom in spring just before the heat nukes them. They are frost-proof sources of winter color. For summer color, buy the increasingly available subtropical and tropical perennials that are waiting for the heat to return and hence aren't at full color in garden shops yet. Until recently most were barely in commerce, with us plant freaks swapping them as cuttings.