Plant parasitic nematode are known to be sensitive to some climatic changes such as temperature, and most stages of nematodes may be killed when exposed to temperatures above 40°C (Santmayer,1955). Hence, during the study, the effect of temperature changes during a year representing the all four seasons (autumn, spring, summer and winter) on the numerical fluctuations in the population density of some parasitic nematodes on plants viz., date palm and olive in both soil and roots was investigated. These nematodes were negatively correlated with the prevailing average soil temperature during four seasons (autumn= 20°C; spring= 22°C; summer= 27°C and winter= 14°C).