This time of year, as the humidity drops in many parts of the country (such as here in Indiana) guitar necks shift a bit, and you may find the action on your axe raising up. Usually, the neck has warped forward a small amount, increasing the bow or relief in the neck.
Here’s a quick, down-and-dirty way to check neck relief: Assuming you are playing a right-handed guitar, fret the first fret on the low E string with your left-hand index finger. Fret the highest fret on the low E string with your right-hand little finger. Use your right-hand index finger to depress the string at the 12th fret. Is there a larger amount of distance from the 12th fret to the bottom of the string than before?
You can also use a feeler gauge to measure the distance from the 7th fret to the bottom of the string, for a more exact reading.
Setting neck relief is a personal preference. Some players prefer a ruler-flat neck, others like a very small amount of relief. Once you have yours set where you like it, make careful notes of where it’s at so you can adjust it back to that point when the humidity changes.