Abstract: Drawing water through open channels is a common way for once-through or recirculating cooling water systems of thermal power plants. Water temperature in open channels is usually rather sensitive to local meteorological conditions due to its large water surface open to the air. In design, attention should be paid to the variation range and trend in the meteorological impact on the water temperature. In this study, thermal dynamics of the water in different climate conditions have been examined by combining numerical simulations and prototype observations on the intake channel of the Dongfang power plant. Results show that in normal meteorological conditions, a weak temperature rising (less than 0.1 ?C) along the channel in the daytime and an even weaker decreasing trend in the nighttime were observed. In the wide seawater intake section of the channel, both the stream-wise rise and the temperature difference between its surface and bottom water layers were larger than that in the inland section. And adverse weather conditions in summer result in a higher stream-wise rise, and cloudless weather produces a stream-wise rise in the daytime significantly larger than that in the nighttime.