Grain can be traded in the futures market before harvest  If the rice production is predicted to be insufficient, the price of rice futures will rise; if the rice harvest is predicted, the price of rice futures will fall  Suppose this morning, Meteorologists predict that it will rain in rice producing areas tomorrow
Meteorologists'forecast of tomorrow's rainfall is likely to extend beyond the grain-producing areas
  Because sufficient rain is very important to the current growth of rice, today's rice futures prices will drop significantly