CA is crazy when it comes to weather seadd67..it changes from month to month, year to year. the only thing I can honestly say that Im sure of when it comes to weather is that in Aug and beginning of Sept. its hot!!! Other than that, its different every year....although I go to DL during all different times of the year, I myself have been at DL during the months of Oct-Dec. for over 20 years straight...Ive done every halloween party except the first one... but even with that said, Oct. is still a nice warm month in the day and it gets chilly at night after the sun goes down...now keep in mind, I live here and since you are from a colder climate then what I consider cool/cold and what you consider cool/cold is very different. Still I dont feel as if Oct. would be shorts weather..the best thing I say to everyone in regards to weather. is to start checking 10 days out with the weather online and keep checking...Even up to 2 days before your trip it could change major...I always suggest layering...take short, capris, jeans etc. and short sleeves and jackets so that way if its too warm you take off..if it gets cool you add