In order for a snowstorm to be classified a blizzard it has to be accompanied by winds over 35 miles per hour, with visibility of one-quarter mile or less. It has to also have temperatures below 20 degrees Fahrenheit and last longer than three hours.
What makes blizzards so unique is that the impact they have is not confined to the duration of the event. They affect the local economic structure before, during and after the storm. Generally, local news stations and weather service will issue advance warnings and tell people to stay off the roads.
While some will stock up on groceries as the warnings arise, unlike with rainy inclement weather there usually aren't big spending sprees at stores. People in cold climates generally know to keep plenty of life saving supplies on hand. However, gas stations see plenty of business just before blizzards as people gas up their cars. Since blizzards can bring really frigid temperatures, it can be hazardous to vehicles to leave gas tanks less than one quarter full.
Also, in cold climates this extra gasoline is needed to let cars sit and idle as to remove snow and ice, as well as let the engine and the interior of the car warm up. This causes more gasoline to be used after blizzards. It's not unheard of for gas stations to try to raise their prices significantly before a blizzard, but local authorities deal with this scenario none too favorably.
During the actual blizzard life pretty much stops. Whole towns and cities shut down, and only emergency personnel is generally active, but even those services function at a bare minimum. This causes a widespread loss of revenue.
The loss of revenue continues even once the blizzard is over. People who have hourly wages often don't get paid for the time off from work, so have less money to spend. There are also extra day care costs for those with children because of school closures.
A lot of people also have extra expenses during the cleanup, so tend to spend less for a while as well. There are some people who benefit financially though: Those who hire themselves out privately to help with cleanup, such as truck drivers with plows.
Due to the cold temperatures that accompany blizzards, doctors and hospitals will see an increase in patients. Injuries range from frostbite due to prolonged exposure to cold and damp temperatures; to heart attacks from shoveling large amounts of snow.
People unfortunately die as well in these conditions, even after the blizzard has passed. This is so because they were stranded and not found in time or because their homes have no heat due to downed power lines.
In essence, when it comes to naturally occurring disasters that leave a devastating economic impact, blizzards are the silent destroyers. Yet, they rarely get as much news exposure as tropical storms or hurricanes. Towns and cities that deal with blizzards year in and year out definitely have their economic challenges.