Aims Tropical cloud forest, a seldom-studied and important type of tropical forest vegetation, is usually distributed around the mountaintops and characterized by unusual environmental conditions which determine the unique biodiversity and ecosystem functioning. Our objective was to explore the characteristics of solar irradiance, air temperature, air relative humidity, soil conditions and topographic conditions in rainy season in two tropical cloud forest communities including tropical montane evergreen forest and tropical montane dwarf forest. Methods Based on surveyed environmental data of tropical montane evergreen forest (TMEF) and tropical montane dwarf forest (TMDF) in Bawangling National Natural Reserve in Hainan Island, we assessed the differences in environmental conditions listed above between the two cloud forests, and examined correlations among the environmental conditions, using a principal component analysis and Pearson’s correlation analysis. Important findings Daily photosynthetically active radiation (PAR) showed a unimodal curve both in TMEF and TMDF, but PAR in TMEF was significantly lower than in TMDF. From May to October, mean daily air temperature differed significantly between TMEF and TMDF and showed a unimodal curve in the two forests, with average values of (21.76 ± 2.44) °C and (19.33 ± 1.03) °C, respectively. Additionally, mean daily relative humidity differed significantly between TMEF and TMDF and showed an inverse “S” curve; average values were (88.44 ± 2.90)% and (97.71 ± 0.80)%, respectively. TMEF had higher total nitrogen, total phosphorous, available nitrogen, organic matter, pH and soil thickness, but lower total potassium and available phosphorous than TMDF. Slope, cover of exposed rock and altitude were lower in TMEF than TMDF, and were significantly correlated with other ecological factors. Principal component analysis and Pearson’s correlation analysis indicated that air temperature, available phosphorous, total potassium, total nitrogen and the three topographic factors were predictors of distribution of these tropical cloud forests.