Below is an article that states much what I suspected. It might've stemmed from sensibility. Darker colors absorb sunlight (heat), and lighter colors repeal sunlight. So staying cool in the summer, makes all the sense in the world.

Some more genteel people have used it to serve their purposes and taken tit a step farther to say it's a fashion faux pas, but it's no longer true. Even if my mom and others still adhere to the "rule".

:)

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One common explanation is practical. For centuries, wearing white in the summer was simply a way to stay cool -- " like changing your dinner menu or putting slipcovers on the furniture. "Not only was there no air-conditioning, but people did not go around in T shirts and halter tops. They wore what we would now consider fairly formal clothes," says Judith Martin, better known as etiquette columnist Miss Manners. "And white is of a lighter weight."

Here is a link that might be useful: Time article

I always wondered where that rule came from, since I did not know it from Germany. Thanks for the info.

Thanks for the information, rob. Very helpful.
I've been following that rule since I came to this country, but I did not know why, and I did wonder what would happen if I did not follow the rules. This must be one of the longest fashion rules around, other than not wearing brown shoes with a black outfit.
Thanks again.

here in Orlando that rule does not apply...thou from habit I still follow it a bit as I grew up in Chicago. I switch to 'winter white' during Dec-Jan (technically we have no winter LOL) then it's spring and reg bright white. ~ liz

It finally dawned on me why that old saying didn't sound exactly right. Around here, it's "don't wear white after Labor Day."

Hi Liz, I remember you and Bigfoot. Glad you posted.