"...what a Chamber-of-Commerce morning it was! The sky was a clean, pure blue, the temperature was warm and, looking north, you could see the snow-frosted mountain peaks."
(from
http://math.ucr.edu/~jdp/Articles/nissan.html)
I suppose "a Chamber-of-Commerce morning" here means "a beautiful morning"? But why Chamber-of-Commerce? It doesn't sound so beautiful though...
I believe it's refering to the fact that the morning was one that the local Chamber of Commerce would be proud to brag about. A Chamber of Commerce is a local governmental body in many cities which tries to increase business, and particularily tourism.
Yeah, it means it'd be a good day for the Chamber of Commerce to brag about the city--it'd especially be a time to take pictures for things like postcards or other materials intended to put the city in its best light. I live in San Diego and I can tell you the vast majority of the pictures taken of the city for promotional purposes are when it's perfectly clear, sunny, and warm,
(the city especially likes to take pictures of San Diegans wearing shorts, sunglasses and sandals in January while much of the rest of the nation is freezing). The days or parts of days when there's a lot of coastal fog are not good "Chamber of Commerce" days for the city (even tho I personally like both the sunny and foggy days, but that's another story).