To illustrate the swing in prices, the study looked at rates for a single, 35-year-old male driver with a $500 deductible and a clean driving record. It found that his insurance was on average 8 percent cheaper in December than March.
The monthly swings in auto insurance rates were much more dramatic in certain states. For example, the median cost of a new auto policy in Hawaii was a whopping 48 percent cheaper in December than March. In Wyoming the difference was 39.7 percent and in the District of Columbia it was 35.3 percent.
The states that experienced the lowest variation in insurance rates were South Dakota (3.7 percent), Arkansas (4.4 percent) and Utah (4.9 percent).
The monthly variation in insurance rates had a lot to do with the the way insurance companies schedule price increases, Eli Lehrer, president of the nonprofit research group The R Street Institute, told insuranceQuotes.com.
"The data shows that it's cheaper to buy insurance in December in most states, and this is almost certainly because a lot of rate increases and new rating plans take effect in January, when the year -- as well as many companies' fiscal years -- begins," Lehrer said.
According to the National Association of Insurance Commissioners (NAIC), the state-by-state differences may exist for several reasons. These include the differences in risks and costs from state to state, bad weather, a change in a state's economic conditions and changes in a state's insurance laws.
insuranceQuotes.com put together a handy calculator so consumers can see how insurance rates are trending in their area. Click here to access the tool.