The monthly figure marked the highest tallied since September 2010 when it stood at 18.8 percent, according to the preliminary data from the Bank of Korea.
Prices of cabbage -- a key ingredient of the Korean traditional side dish of kimchi -- jumped 55.3 percent in August from a month earlier, the BOK said.
Kwon Cheo-yun, head of the price statistics team at the central bank, said rains and a heat wave were to blame for the spike in agricultural goods prices.
Temperatures hovered above 33 degrees Celsius for 24 days across the country in the summer, according to the Korea Meteorological Administration.
Meanwhile, egg prices fell 13.9 percent in August from a month earlier as eggs from local farms were found to be contaminated with banned chemicals.
The BOK said the producer price index -- a barometer of future consumer inflation -- reached 102.20 in August, up 0.3 percent from a month earlier. Year-on-year, the producer price index jumped 3.2 percent in August, marking the 10th consecutive month of gains.
The latest data showed prices of manufactured goods edging up 0.3 percent in August from a month earlier due to the hike in prices of coal and petroleum products. (Yonhap)