1930s Dust Bowl drought explained. Computer artwork showing how, during the 1930s, cooler than normal tropical Pacific Ocean temperatures (blues) and warmer than normal tropical Atlantic Ocean temperatures (red and orange) contributed to a weakened low level jet stream and changed its course, leading to a 'Dust Bowl' drought in North America. The jet stream normally flows westward over the Gulf of Mexico (lower left in each image) and then turns northward pulling up moisture and dumping rain onto the Great Plains. During the 1930s, this low level jet stream weakened, carrying less moisture, and shifted further south. The Great Plains land dried up and dust storms blew across the U.S.