W idely cultivated in the Asian regions, Azolla is either incorporated into the soil before rice transplanting or grown as a dual crop along with rice. To examine the feasibility of its use in flooded rice fields, the study was conducted during 2011-13 with 9 different species/strains of Azolla at BAU Sabour, to study the growth-development dynamics and the resistance/tolerance to extreme temperature which generally occurs in the area. Azolla biomass increased during February- April but suddenly decreased during May-June and again increased during July-September thereafter, biomass decreased during October-January. The correlation coefficient between biomass growth rate of strains A. faliculoides, A. microphylla and BAUAS-1 of Azolla and maximum temperature was found significantly positive. Significant positive correlation between biomass production of species A. faliculoides and strain BAUAS-1 with minimum temperature was found 0.70 and 0.62 respectively, which indicates that increase in minimum temperature up to limit, may increase the growth rate in these strain/spp. There was significant negative correlation (0.70, 0.63 and 0.68) between biomass production rate and relative humidity measured at morning, in the species/strain A. rubra, BAUAS-1, BAUAS-2 respectively. Biomass production rate of azolla species A. pinnata showed significant negative correlation with relative humidity at evening. Significant positive correlation between biomass production and rainfall during the growth period in species A. faliculoides was found, which indicates rainfall or sufficient water increases the growth in Azolla.