Tomaj was attested in historical sources as Thomay in 1494. The name of the village is probably derived from the personal name *Tom(a) (cf. the surnames Filipaj < Filip and Jakaj < Jakob). If so, the name originally designated a place where a person named Toma or Tome lived.[3]
Tomaj has a warm climate for Slovenia. Winters are mild with frequent rain and clouds. Snow is rare and occurs only a few times each winter. Also, sub freezing highs happen just twice a year. Lows hit freezing 68 days annually. Summer's are warm and sunny. Despite being sunny, summers have a lot of rain, with thunderstorms being quite common. There are only 17 days over 30 degrees, and 70 over 25 degrees. Fall is the wettest time of year, and late winter is the driest. Means range from 2.1 in January to 20.8 in July. Tomaj's climate is classified as Cfb or oceanic.