Weather does not sound great for a car show or a booth on Friday. Below is from NOAA for Temecula.
Friday: Showers and possibly a thunderstorm. High near 47. Southeast wind 5 to 15 mph becoming southwest in the morning. Winds could gust as high as 20 mph. Chance of precipitation is 100%.
Friday Night: Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 38. South wind around 10 mph. Chance of precipitation is 60%.
Saturday: A 20 percent chance of showers. Partly sunny, with a high near 55. South wind around 5 mph becoming west in the morning.