Sanmenxia has a mostly dry, monsoon-influenced continental climate with four seasons. Winters are moderately cold and very dry, while summers are hot and humid. Monthly daily average temperatures range from −0.3 °C (31.5 °F) in January to 26.4 °C (79.5 °F) in July, and the annual mean is 13.9 °C (57.0 °F). More than half of the annual precipitation falls from July to September. There are between 184 and 218 frost-free days per annum. In the Köppen system, the city is in the transition zone between a humid subtropical climate and humid continental climate, and receives barely enough precipitation to avoid being semi-arid.