To investigate effects of environmental factors in nurseries on growth of Wasabi (Eutrema japonicum (Miq.) Koidz.) seedlings, they were grown in four different sites in Shizuoka and one site in Yamanashi during summer season in 2021 and 2022. At the end of experiment, ratio of shippable seedlings among the seedlings used for experiment was highest (= 80%) at Yamanashi site, followed by Fujinomiya highland site. At the site of Fujinomiya lowland, no shippable seedlings were obtained. Environmental factors affecting the shippable ratio at individual sites seemed to be different, i.e. air temperature, vapor pressure deficit, or light intensity. A multiple regression analysis was applied to clarify the significant factors affecting the shippable ratio. Accumulated air temperature over 30°C, diurnal range of air temperature, light intensity, and yearly-different growing setup have been revealed to be affecting factors. Using the relationship, suitable sites for Wasabi seedling cultivation during summer season were estimated among 55 sites where meteorological data were provided by Japan Meteorological Agency. The number of the suitable sites were 1, 3, and 20 in Shizuoka, Yamanashi, and Nagano prefectures, respectively. Assuming that air temperature was 1°C higher than average of those during 2021 and 2022, the number of the suitable sites was decreased, but Yamanakako village was left, to which our experimental site in Yamanashi was adjacent.