We investigated differences in interior canopy microclimate between first filial generation (F₁) plants and their parental lines. Our findings suggested genotype-dependent variations in the interior canopy air temperature (T_{a_in}), interior canopy relative humidity (RH_{_in}), and interior canopy vapor pressure deficit (VPD_{_in}). The magnitude and patterns of these differences varied annually and seasonally, with F₁ plants demonstrating lower T_{a_in}, higher RH_{_in}, and lower VPD_{_in} than their parental lines. Similarly, we investigated the interior canopy absolute humidity (AH_{_in}) and interior canopy humidity deficit (HD_{_in}). AH_{_in} showed no clear difference between the F₁s and parental lines, but the F₁ plants exhibited a lower HD_{_in}. Consequently, heterosis may have indirectly influenced sugar beet growth. We hypothesized that these microclimatic factors were associated with differences in the leaf area index (LAI) among genotypes. We assessed the relationships between LAI and T_{a_in}, AH_{_in}, and HD_{_in} and found a significant correlation ( p < 0.05) between HD_{_in} and LAI at 78 d after transplanting (DAT), but not for T_{a_in} ( p = 0.11) or AH_{_in} (ns) at 79-81 DAT in 2017. No significant relationships were observed between any of these parameters at 97-99 DAT in 2018; however, T_{a_in} showed a slight correlation ( p = 0.12). Two factors may explain this year-to-year difference. First, the LAI at 97 DAT in 2018 was lower than that at 78 DAT in 2017, suggesting differences in canopy closure, which likely made vertical exchange easier in 2018. Second, it is possible that wind speeds differed on the observation days. Analysis of wind speeds during the same period suggested that the average wind speed in 2018 was higher than that in 2017. Further research is required to explore the interrelationships among the other factors.