Temecula is comfortable at any time of the year. It averages around the mid-50°s in the cold months of November through March, so bring a hoodie. In the summer months, it hovers around a pleasant 70°.
Although Temecula is a short drive from Los Angeles and San Diego, you can also fly into Ontario International Airport (ONT) - 53 miles from Temecula. Many of the surrounding wineries are most easily accessed by car, while Old Town Temecula is an extremely walkable area. If you prefer not to drive, many local tours tend to offer or provide transportation.