Gap cardigans sold surprisingly well in balmy Miami, and new Boston-based grads spent their gift money on spectator-style Coach purses. In San Francisco, Sephora shoppers sought out self-tanning mist.

That’s a snapshot of shopping trends at three national retailers in three cities of varying personality and climate on a late spring day. The Associated Press asked them to track what was popular and craft mini profiles of the average customer. The idea was to find out what drives sales. Is it the weather? The news? The calendar?

All of the above, according to the companies and consumer behaviorists, but nothing is more important than finding products consumers crave — and that’s the multimillion dollar question in this recession.

Next comes weather. This particular day was partly sunny in San Francisco, with a high temperature in the 60s; Boston was clear skies and 70; and Miami was wet, although still warm. Trouble in the U.S. auto industry dominated the news, along with Congressional oversight of credit cards. It was a Tuesday.

“You might be in the mind set of buying clothes for that particular kind of day,” said Lars Perner, assistant professor of the clinical marketing department of University of Southern California’s Marshall School of Business. “In clothing, you have to be able to visualize yourself in a particular situation, and clothing purchases are caused by the expectation of a change in season.”

There’s also the issue of image, noted Geoffrey Miller, author of “Spent: Sex, Evolution and Consumer Behavior.” Shoppers buy brands with a personality deemed appropriate for their public personas, he said. “What people pay most attention to is their little peer world. They only care about the global economy or even fashion trends when they trickle down locally.”

But Perner says shoppers are also copycats, whether they know it or not: If style influencers start wearing something, the trend can spread. So a paparazzi shot of a celebrity — or, better yet, first lady Michelle Obama — wearing an identifiable look is likely to spur sales “considerably,” Perner said.