Global suicide rates vary by country, yet the cause of this variability has not yet been explained satisfactorily. In this study, we analyzed averaged suicide rates and annual mean temperature in the early 21st century for 183 countries worldwide, and our results suggest that suicide rates vary with climatic temperature. The lowest suicide rates were found for countries with annual mean temperatures of approximately 20 °C. The correlation suicide rate and temperature is much stronger at lower temperatures than at higher temperatures. In the countries with higher temperature, high suicide rates appear with its temperature over about 25 °C. We also investigated the variation in suicide rates with climate based on the Köppen–Geiger climate classification, and found suicide rates to be low in countries in dry zones regardless of annual mean temperature. Moreover, there were distinct trends in the suicide rates in island countries. Considering these complicating factors, a clear relationship between suicide rates and temperature is evident, for both hot and cold climate zones, in our dataset. Finally, low suicide rates are typically found in countries with annual mean temperatures within the established human thermal comfort range. This suggests that climatic temperature may affect suicide rates globally by effecting either hot or cold thermal stress on the human body.