An almanac is a large listing of statistics and information that is published on a regular basis (annually), so an almanac in a dream can represent all of the details, memories and experiences that you have had over a period of time.
Dreaming that you are looking through an almanac is a sign that you are trying to learn more about yourself.
If you are searching through the almanac for a particular piece of information, your unconscious could be telling you that you need to search carefully within yourself for a solution to a waking life problem.
The item that you are searching for, or reading about, in the almanac, can be significant. For example, if you are reading about a particular date, you should ask yourself if that date has any significance for you.
Weather in dreams is often associated with the emotions, so a record of weather in an almanac in a dream can tell you something about your emotional state.