The landscape is dominated by low, rolling hills and basins. The highest point is Munsusan, rising to 736 m on the northern border. Tongrim is drained by the Chongchon River and its tributaries, including the Maryong River and the Kokchon stream. The year-round average temperature is 8.8 °C; the January mean is -8.7 °C, while the August average is 24 °C. Annual rainfall averages 1000 mm. Some 60% of the county is covered by forestland; only 26% of the area is cultivated.
The cultivated land is irrigated, with corps including rice, maize, soybeans, wheat, barley, and tobacco. Aquaculture is also practiced. There are various mines, and factories producing machinery including pumps. The Pyongui Line railroad passes through Tongrim on its way between Sinuiju and Pyongyang.