2m is really odd that way. I work simplex pretty often and the properties are always odd. Some days the same fixed station will be S3, others, 60 over 9 at the same power levels. Used to make me crazy, grabbing my analyzer checking the readings for a bad connection.
Now that the leaves are coming in, you'll notice it more too, particularly up on 440. The winter 'reach' is being filled in again.