In my general area of business (15 miles outside of Flint, MI), I have seen the weather affect my business far more drastically than the economy. Michigan's economy has been in the dump for a bit now, but you would never know it by looking at my business on a sunny weekend. Having said that:
I am not saying it hasn't had an effect, I just think that we (michiganians) have kind of grown numb to it. I haven't had a sunny weekend since September and my numbers reflect that. It is what it is, that is why we all must diversify our services as much as possible, so that we are not such slaves to the weather.
I make a conscious effort every time I talk to someone at the wash, to be positive. I reinforce what a loyal customer base I have. I talk about all the new and great things we are doing. I try and make sure that when they are done speaking with me, they have a smile on their face. As corny as it may sound, it works, give it a try.