<span style="color: black;">The Midwestern United States is preparing for flooding as bitterly cold weather is replaced by a spell of mild weather leading to a rapid thaw. The meteorologists have warned that the fast-rising temperature may not be all good news. <br />''</span><br />'' <span style="color: black;">They have indicated that the thaw may cause a new set of risks, including flooding on streets and in homes, ice jams in lakes, and slippery sidewalks and driveways. <br />''</span><br />'' <span style="color: black;">As temperatures reached 11 to 12 degrees Celsius today in Chicago, schools reopened, businesses resumed and people came back on the streets. <br />''</span><br />'' <span style="color: black;">According to the World Meteorological Organization, the harsh weather was caused by the influence of the Arctic polar vortex.</span><br />