The April average temperature for the U.S. was 49.7°F, which was 1.4°F below the 20th century average. In climate speak that is significant. April 2013 ranked as the 23rd coolest such month on record and marked the coolest April since 1997 when the monthly average temperature for the contiguous U.S. was 48.0°F. Rainfall and cloud cover played a major role in these numbers according to the National Climatic Data Center.
According to NOAA's National Climatic Data Center the April average precipitation for the contiguous U.S. was 2.90", 0.47" above average, and tied with 1953 as the 19th wettest April on record.
Source: NOAA's National Climatic Data Center