The month of April is typically 10.5 degrees milder than the month of March. So far this April (2015), however, the first two weeks have been chillier than March (which was the fourth mildest on record). This made me curious about whether there have been any Aprils that were colder than March (going back to 1870). The answer is no. The closest this came to happening was in 1946 when April was 0.6 degrees milder than March. The chart below lists the five Aprils that were closest to March's average temperature. (April 2015 would end up being 4.4 degrees milder than March, not close enough to March to place on the chart below.)
And although April 2012 wasn't chillier than March, it did have one fewer day in the 70s than March (six versus seven).