West Coast USA has been flooded, when a ship carrying water bottles hit the edge of the water, all of the bottles exploded causing a lot of rain evaporating at once. This cause lots of torrential rain, luckily the highest points in the city were not affected, nor the highways or the neighbourhood, however, everyone in the hospital was evacuated, causing some serious problems. Get out of the city as fast as you can to avoid the inevitable fate of your vehicle's engine hydrolocking..
Speirs has made a video on this map in Version 1.0! Check it out, send him some love