I'm very new at car washing but have been detailing for almost 2 decades. I had a super February 2007 at the wash and did well all Winter last year. This January was up over 2007 for car wash sales. Detail shop was down very slightly, same time period.
This year in the Northeast car wash volume has been up and down. We've gotten plenty of hard, winter weather. Plenty of storms followed by a thorough salting of the roads. Maybe too much! I think the 'x' factor for me is weekend weather. If the temps are above 20 F, the sun is out, and it's not too windy, we wash alot of cars. If these factors are out of whack, volume drops. These factors carry over to weekdays, though it is to a lesser extent. But nice weather during the week also encourages washing.
The evidence of the effects of weather on the car care biz are also evident in the f.s. detail end. Today, it's sunny and low-mid 30's. Typically Mondays aren't too busy, but I've booked about 6 or 7 detail jobs so far, from my $40 wash, vac and windows job to basic recons (paste wax and complete interior detail). By day's end, I'll book a dozen details total, I'm certain.
So, yeah, it's the weather for me, personally. I'm not one to believe quite all the tales of a poor economy causing volume dips for us; I've got hard data I go by in the amount of people willing to spend $150 on a full detail in Winter. Today there are some of those being booked, so I feel good about that.