The April average temperature for the contiguous U.S. was 49.7°F, which was 1.4°F below the 20th century average. 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.
Near and above-average temperatures were present along the U.S. East Coast and in parts of the West. California had its 12th warmest April on record with a statewide temperature 3.7°F above average.
The April average precipitation for the contiguous U.S. was 2.90 inches, 0.47 inch above average, and tied with 1953 as the 19th wettest April on record.
The Northwest, Midwest, and the Southeast were wetter than average. Iowa and Michigan both had their wettest April on record. The Iowa statewide average precipitation total of 6.71 inches was 3.76 inches above average; the Michigan precipitation total of 5.97 inches was 3.29 inches above average. Additionally, Tennessee, Illinois, Indiana, and Wisconsin each had one of the ten wettest Aprils on record.
The wet conditions in the central U.S. resulted in several rivers in Illinois, Iowa, and Michigan reaching record high levels, with widespread flooding observed. The Mississippi River at St. Louis also reached flood stage after dropping to near-record low levels at the beginning of the year.
Alaska was much cooler than average during April, with a statewide average temperature 5.8°F below the 1971-2000 average. This was the 7th coldest April in the 96-year period of record for the state, and the coldest April since 1985. The average temperature in Fairbanks was 14.5°F below normal and the coldest April on record for the city.
According to the April 30 U.S. Drought Monitor report, 46.9 percent of the contiguous U.S. was experiencing moderate-to-exceptional drought, smaller than the 51.9 percent at the beginning of the month. Drought conditions continued to improve across the Southeast, Midwest, and along the northern and eastern periphery of the core drought areas of the Great Plains. Drought conditions worsened for parts of the Southwest, and drought continued for much of the Great Plains and Mountain West.
Several storms impacted the U.S. bringing record-breaking, late-season snowfall to central United States. According to data from the Rutgers Global Snow Lab, the April snow cover extent for the contiguous U.S. was approximately 480,000 square miles, 209,000 square miles above the 1981-2010 average and the 5th largest April snow cover extent in the 47-year period of record. However, dismal snowpack continued in parts of the West, with only 18 percent of normal snowpack reported in the Sierra Nevada Mountains.
The U.S. Climate Extremes Index (USCEI), an index that tracks the highest and lowest 10 percent of extremes in temperature, precipitation, and drought across the contiguous U.S., was slightly above-average during April. The above-average CEI was driven by extremes in cold daytime and night time temperatures, 1-day precipitation totals, and the component that examines the spatial extent of drought.
Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand was slightly above average (109 percent of average) during April and ranked as the 50th highest April value in the 119-year period of record.
The first two months of the spring season, March-April, were cooler than average for the contiguous United States. The nationally-average temperature for the two-month period was 45.2°F, 1.1°F below average and the 33rd coolest March-April on record. This marked the coldest such 2-month period since 1996.
Below-average temperatures stretched from the Northern Plains to the Southeast, with 16 states having one of the ten coolest March-April periods on record. Above-average temperatures occurred in the Northeast and West. California had its fifth warmest March-April and Arizona had its eighth warmest.
Wetter-than-average conditions stretched from the Great Lakes, along the Mississippi River Valley, and into the Southeast. Michigan and Wisconsin each had their wettest January-April, with precipitation totals 5.26 inches and 3.62 inches above average, respectively. Minnesota, Iowa, Missouri, and Illinois also had a top ten wettest year-to-date period.
Much of the western and northeastern U.S. was drier than average during January-April. In the West, California had its driest year-to-date with a statewide precipitation total of 3.59 inches, 9.49 inches below average. Oregon, Nevada, and Idaho each had one of their ten driest year-to-date periods. In the Northeast, Connecticut, Maine, New Hampshire, and Vermont also had a top ten dry January-April.
The year-to-date USCEI was near-average. Despite the near-average USCEI, the extremes in 1-day precipitation totals and the component that examines the spatial extent of drought were both much above average.
