Ø  It is a semi aquatic plant and hence, its water requirement is very high. rice can be grown in pre - kharif, kharif, as well as in rabi seasons proving its wider adaptability to varied climatic conditions.

Ø  20 - 360C average day temperature with night temperature 20 -230C are ideal for its growth.

Ø  The crop can tolerate 19OC TO 40OC the optimum temperature required for germination is at least 10O C; for flowering IS 22-230C and for grain formation is 20-210C.

Ø  A mean air temperature of around 22OC is required for the entire growth. very high temperatures alongwith high wind speed cause sun burning and scald diseases. low temperature reduces formation of spikelets, germination, seedling development, tillering and shoot height.

Ø  Soil temperature above 160C after transplanting is very essential. light intensity upto 200% of normal gives more tillers, panicles and well developed grains.

Higher RH (%) within the crop canopy is usually conducive

Ø  For obtaining the maximum yield the accumulated sunshine hours during the crop span of rice is 1000 with 220 - 240 hours in the  last 30 days.

Rice has very high water requirement. optimum well distributed rainfall during its almost  4 months growing period is 1120 to 1500 mm.  standing water from end of tillering to grain ripening is useful. the crop is highly sensitive to water deficiency at flowering and heading stages

Ø  Total water requirement of the crop varies from 80 to 180 cm depending upon crop variety, local climate, growing season and soil type.

Ø  In kharif season, when humidity is high and evaporative demands are low, maintenance of continuous submergence is not essential but during rabi season it is required. great economy in water use by rice crop can be achieved if suitable measures are adopted to reduce the deep percolation losses, by suitable irrigation techniques.