Here are some forecast temperatures for Sundays ride. Most of the early part of the ride and climbing the East grade should be bearable. The Cole grade climb looks like it's going to be in the low 90s
Valley Center
http://forecast.weather.gov/MapClick.php?lat=33.2184&lon=-117.0342&unit=0&lg=english&FcstType=text&TextType=1
Palomar Mt
http://forecast.weather.gov/MapClick.php?lat=33.3634&lon=-116.8361&unit=0&lg=english&FcstType=text&TextType=1