On that NWS pages, the upper map(s) is(are) for temperature and the lower map(s) for precipitation. Clicking a map opens it in a larger format to allow a closer look.
The three letters before the year (eg. ASO) are the letters for the months.
ASO = August September October
SON = September October November
OND = October November December
etc. . . .
Note: The Contra Costa County Flood Control & Water Conservation District does not provide weather forecasts or predictions. Some NWS pages are experimental and their web addresses and content change from time to time.