Whenever you are facing a risk, you want to be able to hedge against it (at least if you are risk averse). For this, there are all sorts of insurance policies. There are also markets in all sorts of instruments that allow you to find the right contingent claim for your situation. This includes farmers (and others) who want to hedge against meteorological risks. If you crop yields depend on weather patterns, you are looking for securities that pay out depending on some weather statistic. And they are available and have been heavily pushed by aid agencies in developing countries.
Chiratan Banerjee and Ernst Berg say they may not be such a great idea. They take the examples of rice farmers in the Philippines who bought wind-speed based indexes on the hypothesis that rice yields are lower when there are typhoons. But rice is remarkably resistant to typhoons and wind in general, the reason why it is so popular in the region in the first place. This means that rice farmers are heavily over-insured. That is especially bad and farmers are now confused about the concept of insurance as it looks like they face more risk than before.