In order to evaluate the effect of environmental conditions in different areas and years on seed-borne fungal diseases of hybrid maize seed, an experiment performed in sub-plot design in two years and three main areas of maize seed production areas in Iran. Parental lines of 704 hybrid were cultivated in three planting date and five different female densities for more diversity of environmental conditions. Assessment of Fusarium ear rot, Penicillium and Aspergillus infection was done after harvesting. The results showed that the effect of planting area, planting date and plant density on the percentage of seed fungal infection was significant and different in two years. By increasing in plant density, fungal infection significantly increased. Simple and binomial regression model between meteorological data and infection showed that very high and very low temperature and relative humidity increased seed fusarium infection. Increasing in the relative humidity caused an increment in the rate of Penicillium infection. In this study, there was found that the percent of fungal infection was reduced by increasing in sunny hours or decreasing in the degree of cloudiness. All the fungal infections were increased by increasing rainfall during the development and maturity maize seeds. So for decreasing the infections, it is more appropriate to produce the maize seeds in the regions that have higher average of sunny hours during development and prevent the encountering the harvest time to fall raining.