Warmer-than-normal temperatures rapidly melt snow and ice on the upper <a href="https://en.wikipedia.org/wiki/Allegheny_River" id="mwlQ" rel="mw:WikiLink" title="Allegheny River">Allegheny</a> and <a href="https://en.wikipedia.org/wiki/Monongahela_River" id="mwlg" rel="mw:WikiLink" title="Monongahela River">Monongahela</a> rivers, leading to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pittsburgh_Flood_of_1936" id="mwlw" rel="mw:WikiLink" title="Pittsburgh Flood of 1936">a major flood in Pittsburgh</a>.