I will travel to the United States for half a month in mid-January, including Los Angeles, San Francisco and Las Vegas. I wonder what the weather is like there. What clothes are appropriate to wear?

There is a great temperature difference between these three places in the morning, afternoon and evening. You should wear sweater+jacket in the morning, short-sleeved shirt at noon and dressing gown at night. The large temperature difference is especially obvious in Las Vegas, where the desert climate is authentic. The temperature difference in San Francisco is not obvious. 5- 15℃ in the morning, 20-30 at noon (super hot when the sun is shining), and 5- 15 at night.