Severe overnight thunderstorms dumped several inches of rain across Chicago and northwest Indiana on 19 Aug., inundating neighborhoods, swamping basements and knocking out power to parts of the region. Local officials said as many as 200 homes in Hammond alone were flooded, and meteorologists described the event as the worst regional flooding in decades. The deluge forced BP to halt several processing units at its 440,000-barrel-per-day Whiting refinery— the largest fuel plant in the U.S. Midwest—and to burn excess hydrocarbons in flare stacks to keep the site safe. Consultancy Wood Mackenzie said both fluid catalytic cracker units, two crude distillation units, a vacuum distillation unit and multiple hydrotreaters were taken offline after water entered the facility. BP confirmed that operations were ‘impacted’ but did not specify the extent of output loss. The refinery supplies gasoline, diesel and jet fuel to much of the upper Midwest, and any prolonged outage could tighten already thin regional inventories. Wholesale markets reacted quickly: Chicago-area conventional gasoline (CBOB) narrowed its discount to New York Mercantile Exchange futures to 4 cents a gallon from 9 cents the previous session. Traders said further gains are possible if the shutdowns extend into the week.