The so-called "agricultural characteristic temperature" denotes the daily mean temperature of 0°, 5°, 10° or 15°C and accumulated temperatures of 10°C up. Every different mean temperature is chaaacteristic of a certain rural phenomenon, e，g., daily mean temperature above 0°C charactsrizes the farming season; above 5°C, the period of growth; above 10°C, the time of buoyant growth; and above 15°C, the period for planting cotton and rice. The accumulated temperatures of 10°C up are to a certain degree correlated with the distribution of crops.