Tips from Delivery Guys:
http://www.nytimes.com/2005/03/02/dining/02guys.html Excerpt:
"Our guys wish every day for snow or rain," said Tommy Chu, a manager at Ollie's. "Sunny days are no good for tips."
(end)
Of course, that makes perfect sense and I should have realized that, but I have always been one of the many people who feels sorry for them when there's bad weather outside.