What does this Practice Note cover? This Practice Note explains what weather derivatives are, their purpose and applications and the regulatory framework governing their use. For information about sustainability and environmental, social and governance (ESG) derivatives generally, see Practice Note: ESG derivatives. What are weather derivatives? The weather risk market is designed to assist users in managing the adverse financial impact of weather through risk transfer instruments based on weather variables (chiefly temperature, rain, snow, wind and sunshine). Solutions to the problem of weather-related financial risk will normally take one of two principal forms: catastrophe insurance or weather derivatives. While catastrophe insurance is suitable for addressing low probability weather risks with a high potential impact, such as severe drought or flooding, weather derivatives are better suited to low impact/high probability events such as an unseasonably cool August or an unusually wet May Bank Holiday. One of the advantages of standardised weather derivatives for low impact events is that pay-out will occur automatically once the index sinks or rises past a certain point. In contrast, to recover under