Last December I had the slowest month in 5 years. Then in March it was the busiest month in over 14 years. You can do all you want to increase sales, but the weather really makes or breaks this business.
It's so true; we had a poor washing season this past Winter due to too many storm events / precip. too frequently. The wash never got any good traction of a week or 2 of dry weather with warm enough temps to get customers washing the car. The past month has been very good, though, so we have bounced back somewhat.
What has helped is diversification; for us it has been used car sales, detailing, and an 8 plex apartment building.