Ok, we have premium passes and go frequently, here is a good rule of thumb (doesn't always work, but is about 90% accurate):
I will list the days of the week from lightest crowds to heaviest crowds below.
Off Season:
Wednesday
Tuesday/Thursday
Monday/Friday
Saturday
Sunday
Note: Dates that are blackout dates for the So. Cal Select and So. Cal passes will be busier compared to the same day of the week., dates where Deluxe passes and below are blacked out will be lighter compared to the same day of the week.
Peak Season:
Monday-Friday
Saturday
Sunday
Note: The more levels of passes that are blacked out, the lighter the crowds will be. I know this seems counter intuitive, but this is based on what we have seen personally.
I would generally define Off Season as Mid January - Mid March, Last week of April - Week before Memorial Day, day after Labor Day - Sept. 30th, First two weeks of November, first week of December. Please be aware that if any of the following are happening, then that time frame should be considered peak season:
- Halloween Time
- it's a small world holiday has opened (except the first week of December)
- Opening of Carsland
- Spring Break for ANY school in the U.S.
- The entire week of Thanksgiving
- First two and last two weeks of ANY So. Cal. promotion
In general to determine if Christmas Eve will be busy, look at Christmas Eve last year and see if there were reports of massive crowds, if there were then generally the crowds will be EXTREMELY light, if there weren't, then generally the crowds will be EXTREMELY heavy.
Also, rain (particularly heavy rain), even if it only lasts 30 minutes will usually reduce the crowds by about 40% (on busier days I have seen it reduce the crowds by about 80%, especially on new Year's Eve).
Aside from Cars Land, if a major attraction is opening, crowds will be generally light on all other attractions on opening day, this effect lasts for two-three days, then everything starts getting a lot busier.
Again, your mileage may vary, as this is based solely on our (and our friends') experiences.
Another thing to look at is when the resort hotels offer the lowest rates (or best specials), that generally indicates that they will be less crowded as they want to attract more people.