Here are various sources for weather at Santa Anita Park in Arcadia, CA. You may wish to check several and try to come to a consensus as to just what the weather will be like, but unlike other regular Breeders' Cup venues, the weather here is quite consistent.
Average high temperature on November 1 is 76 degrees with an average low of 53, while the record high is 97 degrees in 1949. The high temperature on November 1 at Los Angeles International Airport (LAX) has ranged from 59 to 98 in the last 15 years but only went higher than 70 five times. The average rainfall for November is 1.29 inches, so there is a slight chance of wet weather. Late December through February is the most rainy time of the year there, so hopefully it won't rain in early November. With the return to a dirt track after several years with a Pro-Ride synthetic track, rain can affect the surface. Santa Anita's turf course is a Bermuda grass hybrid, a very dense short "carpet", in contrast with the taller Kentucky Bluegrass and Red Fescue that are used at the eastern tracks.
Note that Santa Anita is about 30 miles northeast of LAX and is more affected by the hot dry Santa Ana winds from the Mojave Desert as opposed to the cool humid breezes from the Pacific Ocean. Some years the dry air can lower the relative humidity down to 5% or less which can cause wildfires, as was experienced during the 2003 Breeders' Cup. That year, smoke obscured the usually stunning backdrop of the San Gabriel Mountains and a thin layer of ash coated cars in the parking lot.
So when checking forecasts or current conditions on your own, look up the weather in Arcadia or Pasadena rather than at LAX. The track did experience some rain on the Monday before the 2014 Championships but the track easily absorbed this and the track was dry later in the day.
Review: Crushing the Cup 2016 - by Jim Mazur and Peter Mallett. An invaluable tool for trying to unlock the mysteries of handicapping the Breeders' Cup races at Santa Anita. Updated for 2016, this is their 25th anniversary edition.
The Breeders' Cup Championship Day - The official page for the Breeders' Cup championship races. Just about anything you need to know about it: results, video clips, and race calls for past years, and eventually nominations, entries, and results.
Free Prep Replays - for major prep races in the Breeders' Cup Challenge. The ones with camera logos have video available.
Breeders' Cup Supplemental Entries - The old official policy on supplemental entries plus all the supplemental entries and how they fared, mostly it was a losing proposition. There are no more supplements now, only late nominations making it impossible to track now.