Weather derivative with a reference point based on an expected rainfall level in a specific location over a defined period. If the point is exceeded, certain entities, e.g. a theme park, will suffer poor sales and receive a payout based on the accumulated deviations above the rainfall index multiplied by the tick. If the actual rainfall level does not exceed the reference point (or strike) there is no payout; the only cost to the firm is the premium paid in return for the protection granted. See PRECIPITATION SWAPS; SNOWFALL COVER.