Raids continued late into the war. As part of the campaign against German oil facilities, the RAF raid of 20–21 February on the Rhenania Ossag refinery in the Reisholz district of the city halted oil production there. The Allied ground advance into Germany reached Düsseldorf in mid-April 1945. The United States 97th Infantry Division easily captured the city on 18 April 1945, after the local German Resistance group launched Aktion Rheinland. In 1946, Düsseldorf was made capital of the new federal state of North Rhine-Westphalia. The city's reconstruction proceeded at a frantic pace and the economic transformation guided Düsseldorf's economic growth. Düsseldorf lies at the centre of the Lower Rhine basin, where the delta of the Düssel flows into the Rhine. The city lies on the east side of the Rhine, except District 4 (Oberkassel, Niederkassel, Heerdt and Lörick). Across the Rhine, the city of Neuss stands on the delta of the Erft. Düsseldorf lies southwest of the Ruhr urban area, and in the middle of the Rhine-Ruhr metropolitan region. Düsseldorf is built entirely on alluvium, mud, sand, clay and occasionally gravel. The highest point in Düsseldorf is the top of Sandberg in the far eastern part of the city (Hubbelrath borough) at . The lowest point is at the far northern end in Wittlaer borough where the Schwarzbach enters the Rhine, with an average elevation of . The following districts and cities border Düsseldorf (clockwise starting from the north): the City of Duisburg, the District of Mettmann (Ratingen, Mettmann, Erkrath, Hilden, Langenfeld, and Monheim), and the District of Neuss (Dormagen, Neuss, and Meerbusch). The city has an oceanic climate (Köppen: "Cfb", mild in relation to East Germany). Like the rest of the lower Rhineland, Düsseldorf experiences moderate winters with little snowfall and mild to warm summers. The average annual temperature is with an average yearly precipitation of . The dominant wind direction is from the west with velocities in the range of 3 to 4 m/s (7–9 mph), with gusts of 3.5 −4.8 m/s (8–10.7 mph).