As the weather turns chillier and some areas of the country experience the year's first freezing drizzle or dusting of snow, people's buying habits tend to change, sometimes without them even realizing it. In department stores, shoppers reach for plush down coats or cozy scarves; in the grocery store, they snap up comfort food and soups. At the car dealership, buyers gravitate toward four-wheel-drive vehicles.

This may seem obvious - the seasonal surge in ice cream or warm winter boots, for example. But its effect can be subtle and surprising. These days, many businesses are tracking minute changes in the weather as a way to figure out what customers want -- from hair products and quilting supplies to McRibs and insurance - often before they even know they want them.

Marketers have long designed their product releases and advertisements to capitalize on these trends.

Comfort food, for example. If you find yourself reaching for heartier and richer foods as the temperature drops, you're not the only one. Google's data show that Internet searches for pork chops, meatballs, chocolate chip cookies, apple streusel, French toast and other comfort foods spike during the winter and when blizzards occur.


Google Trends ranked the top five most searched comfort foods across the U.S. during last winter. This map shows the most-searched-for term among those top five food terms.

Last winter, it seems, most of America was hungering for pork chops. However, Oregon searched for lasagna and Utah for chocolate chip cookies, while California and much of the East Coast were firmly meatball territory.

The food industry tries to seize on weather-related cravings through targeted advertising. Campbell Soup Co. uses a kind of "misery index" that tracks when the weather takes a nasty turn in U.S. cities, and then cues up soup ads in those markets.

In early November, McDonald's announced that it would begin using digital menu boards that will change offerings based on the local weather and the time of day. When it's hot outside, expect to see McFlurries; when it's cold, heartier meals and hot beverages.

Forecasts can also help supermarkets know what to stock. Research by Tesco, a British supermarket chain, has reportedly shown that when the temperature outside rises from 68 to 75 degrees Fahrenheit, sales of hamburgers increase by 42 percent as people start to barbecue. Demand for coleslaw also soars, while purchases of green vegetables fall.

In retail, the onset of winter marks a big shift. Since fall and winter clothing tends to be bulkier and more expensive than spring and summer clothing, a long, warm fall -- like the one the East Coast is experiencing -- can weigh heavily on the bottom line. Earlier this month, Macy's, Gap and Kohl's all reported disappointing quarterly earnings, in part due to unseasonably warm weather that limited demand for winter clothing.

Weather has long been a recognized influence on energy companies, food, airlines and retail. But these days, data tracking and predictive technology allow advertisers to determine the effects of weather on almost every product -- including yogurt, hair products and quilting supplies. Marketers are also able to track and analyze tiny weather differences within a state or a county, down to the Zip code.

In one example, Michaels, a craft store, discovered that it could increase sales by running its ads ahead of rainy days, when its customers like to stay indoors and work on craft projects. In another example, Pantene Pro-V Smooth had success marketing its smoothing hair products in parts of the country with spiking humidity, and its volumizing products in drier locales.

The secret to weather-related marketing is that the way people experience weather is relative, says Jeremy Steinberg, global head of sales at the Weather Company, which owns the Weather Channel. As any frost-hardened northerner will tell you, an inch of snow in Boston or Minnesota is very different from an inch of snow in Washington or Atlanta.

Other factors: cloud cover, wind speed, humidity, what the weather was like yesterday and what it will be tomorrow, Steinberg says. These trends can differ based on your immediate location -- what researchers call a microclimate.

"When you think about it, weather is not really absolute -- it's a mix of conditions that really creates to a consumer a 'feels like' state," Steinberg says.

Because these trends are so complex, it can be hard for brands to know how to respond to them. The Weather Company has built a platform that monitors weather and places advertisements in response to local "weather triggers."

One example is a partnership between The Weather Company and GlaxoSmithKline, which makes an allergy medication called Flonase. Together, the companies launched an allergy tracker that shows users a three-day outlook for levels of pollen, mold and air quality in their immediate area, as well as timely advertisements for Flonase.

"Companies have known for quite some time that weather does significantly impact their business," Steinberg says. "What we've done is we've unlocked this huge new potential to do it at scale and in an automated fashion."

The Weather Company has also helped to market those Pantene hair products, he says, as well as insurance policies. People in areas experiencing severe or inclement weather might see a message to drive safely, which insurers hope will reduce accidents and save them money.

Weather influences people's health, moods and expectations of what they will enjoy in the future. Weather has been known to affect blood pressure, suicide rates and even a person's ability to concentrate.

One study led by a professor at Harvard Business School, which looked at the productivity of a bank in Tokyo over a period of two and a half years, found that employees were able to process loan applications, an activity which requires focus, a lot more quickly on rainy days than clear, sunny ones. The researchers concluded that nice weather caused more "cognitive distractions."

The overall effect was so large -- amounting to $937,500 in lost revenue for that bank per year -- that the researchers argued that companies might want to set up their headquarters in places with more miserable weather, or save more difficult work for particularly dismal days.

Standard economic models presume that people have a good idea of how valuable products and services will be to them in the future.

But psychological studies show that people are generally pretty bad at predicting how their future tastes will differ from what they want now. This is why shoppers might avoid going to the grocery store on an empty stomach, lest they end up with a refrigerator of food they don't need.

A 2012 study found that "projection bias" -- the tendency to overpredict how much our current tastes and preferences will match our future ones -- affected what cars and homes people buy.

That study, which looked at sales of 40 million cars and 4 million houses over a decade, found that sales of convertibles, black cars, four-wheel-drive vehicles and houses with swimming pools were all correlated with the current weather.

For example, sales of convertibles peaked in April, and spiked by about 8.5 percent when the mean temperature was 20 degrees higher than normal. The researchers also found that cars bought on days with abnormally nice weather were more likely to be returned quickly, suggesting some impulse buys.

The graphs below show the seasonal rise and fall in the percentage of convertibles sold, on the top, and four-wheel-drive vehicles sold, on the bottom:


Projection bias in the car and housing markets, Busse et. al.

According to their figures, a snowstorm of roughly 10 inches increased the number of four-wheel-drive vehicles sold by about 6 percent over the next two to three weeks. Meanwhile, houses with swimming pools that went under contract in the summer sold for 0.4 percentage points more than similar houses in the winter, the study found -- a difference of about $1,600.

Consumers may not even notice how weather affects their purchases. But if you're thinking of buying a convertible, it may be best to wait for a cloudy day.

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