Jamieson, Fausset and Brown on Jeremiah 50:38

38. drought--Altering the pointing, this verse will begin as the three previous verses, "A sword." However, all the pointed manuscripts read, "A drought," as English Version. Cyrus turned off the waters of the Euphrates into a new channel and so marched through the dried-up bed into the city (Jr 51:32). Babylonia once was famed for its corn, which often yielded from one to two hundredfold [Herodotus]. This was due to its network of water-courses from the Euphrates for irrigation, traces of which [Layard] are seen still on all sides, but dry and barren (Is 44:27).

their idols--literally, "terrors." They are mad after idols that are more calculated to frighten than to attract (Jr 51:44, 47, 52; Da 3:1). Mere bugbears with which to frighten children.