In equatorial, hot-humid tropical climates, users of naturally ventilated environments are commonly susceptible to heat discomfort caused by high air temperatures and thus require more air movement to improve thermal comfort. To evaluate the influence of relative humidity and air speed on the occupant's thermal perception, field studies were conducted in naturally ventilated and fan-assisted classrooms in São Luis City, North-Eastern Brazil. Indoor environmental variables were measured alongside questionnaires, focusing on thermal environment and air movement evaluation. The results indicated that relative humidity had a significant negative impact on thermal perception when the operative temperature was above 30 °C, while airspeed played a key role in reducing thermal discomfort. Despite the contribution of internal air movement, it was concluded that, when the indoor operative temperature exceeded 31 °C, mechanical cooling is required to achieve thermal comfort. The results also indicated the great acceptability of indoor conditions, as well as the influence of environmental variables on student's thermal perception in naturally ventilated spaces. •Air humidity had significant impact on thermal perception in a warm environment.•Air movement attenuated heat sensation when operative temperature was below 30 °C.•Air speeds of 1 m/s and above had no additional cooling effect at 31 °C.•Operative temperature above 31 °C was unacceptable, as it was 30 °C with least 70% RH.