I've been there the past 4 Octobers and will be there the first weekend in October this year for a day-trip. It's been hot each time during the day, cooler at night. As others have said, bring layers. I think it's typically in the 80s during the day and 50s-60s at night. It can be slightly cooler, but in early October, more likely it will be warmer. There's also always a chance of high winds that time of year, but they will be hot, dry winds.