Weather Derivative

A weather derivative is a financial instrument used by companies or individuals to hedge against the risk of weather-related losses. The seller of a weather derivative agrees to bear the risk of disasters in return for a premium. If no damages occur before the expiration of the contract, the seller will make a profit. In the event of unexpected or adverse weather, the buyer of the derivative claims the agreed amount.

Companies whose business depends on the weather, such as hydro-electric businesses or those who manage sporting events, might use weather derivatives as part of a risk-management strategy. Farmers may use weather derivatives to hedge against a poor harvest caused by too much or too little rain, sudden temperature swings, or destructive winds.

Weather derivatives typically have a basis to an index which measures a particular aspect of weather. For example, an index might be the total rainfall over a specified period in a specific place. Another can be for the number of times the temperature falls below freezing. 

One climate index for weather derivative is known as heating degree days or HDD. Under HDD contracts, each day the daily mean temperature falls below a predetermined reference point over a specified period, the amount of the departure is recorded and added to a cumulative count. The final figure determines whether the seller pays out or receives payment.

Weather derivatives, developed in the 1990s, fill an unmet need in the economy. The weather impacts roughly 20% of the U.S. economy. Agriculture, energy, travel, and construction are examples of industries in which weather plays an especially important role. But unexpected weather rarely results in price adjustments which entirely make up for lost revenue. Weather derivatives allow companies to hedge against the possibility of weather that might adversely affect their business.

In 1997, weather derivatives began trading over-the-counter (OTC), and within a few years, they had become an $8 billion industry. The Chicago Mercantile Exchange (CME) lists weather derivative contracts for a few dozen cities, the majority of them in the U.S. Some hedge funds treat weather derivatives as an investment class. Investors who like weather derivatives appreciate their low correlation with traditional markets. 

Weather derivatives are similar to but different from insurance. Insurance covers low-probability, catastrophic weather events such as hurricanes, earthquakes, and tornados. In contrast, derivatives cover higher-probability events such as a dryer-than-expected summer.

Insurance does not protect against the reduction of demand resulting from a slightly wetter summer than average, for example, but weather derivatives can do just that. Since weather derivatives and insurance cover two different possibilities, a company might have an interest in purchasing both.

Also, since the contract is index-based, buyers of weather derivatives do not need to demonstrate a loss. In order to collect insurance, on the other hand, damage must be shown.