Several studies have been displayed temperature as one of the factors inversely associated with COVID-19 transmission (3–5, 8–10). But some other studies have not been attributed such a major impact to temperature and relative humidity (1, 11, 12). Briz-Redon et al., in a study, stated that It seems the reports demonstrating the impact of warm climate on the risk of transmission of COVID-19 cannot be satisfying for controlling the pandemic. Moreover, they suggested selecting data from small areas, for example, a single country might be more advisable for such analysis (3). Huang et al, reported that 60% of confirmed COVID-19 cases occurred in spaces with the temperature ranging from 5°C to 15°C (8). Similarly, Sobur et al., showed 93.5% of confirmed COVID-19 cases occurred in temperature between 1°C to 16°C (1). The present study found the cumulative COVID-19 incidence rate was roughly declined at 20 to 35°C. It appears that the higher rates of disease transmission at both lower and higher temperatures might be due to the indoors gathering of people in cold and warm temperatures’ that is, doors and windows are closed at houses, offices, and public buildings to prevent energy-wasting, which cased to the insufficient ventilation of indoor spaces and subsequently, higher risk of disease transmission. By and large, as this is strongly proved that sufficient ventilation at closed spaces can reduce transmission of disease (13), perhaps the temperature itself does not control the transmission of disease and it would be rather related to the proper social response to the temperature fluctuations. However, this is just a hypothesis, which needs to be further established. In addition, in contrast with in-line publications, we did not find high incidence rates at low temperatures. One explanation might be the indirect social isolation in very cold weather. A major limitation of our study was about lack of accounting for several major protective measures against COVID-19 transmission including adherence to social distancing, wearing masks, and hand hygiene as confounders (13).