April 2010 state temperature rankings. Source: NOAA. Click to enlarge.

Based on a 116-year record since 1895, this monthly analysis prepared by scientists at NOAA’s National Climatic Data Center in Asheville, NC, is part of the suite of climate services NOAA provides.

• The generally warm and dry influence of persistent high-pressure areas brought above-normal temperatures to most states east of the Rocky Mountains. Only three states (California, Nevada and Oregon) had cooler-than-average temperatures in April.

• Regionally, both the Northeast and the East North Central Region near the Great Lakes experienced their second warmest April on record. The Central climate region was also saw above-normal temperatures, resulting in the fourth warmest April for that region.

• Record warmth prevailed in Illinois and the northeast, namely Maine, Connecticut, Rhode Island and New Jersey, each of which had its warmest April on record. In total, 31 states had above-normal temperatures.

• The three-month period (February-April) was the record warmest in six states; Maine, Vermont, New Hampshire, Massachusetts, Connecticut and Rhode Island. Maine, Vermont and New Hampshire each also had their warmest year-to-date (January-April) period on record.

• Conversely, Florida had its coolest, while South Carolina, Georgia, Alabama, Mississippi, Louisiana and Texas’ average temperature ranked among their 10 coolest.

• The cooler-than-normal temperatures that prevailed during the latter part of the winter season in the south and southeast were still evident in the three-month (February-April) period. Florida had its coolest such period, while Louisiana and Alabama had their sixth coolest, Georgia its seventh coolest and both Mississippi and Texas their eighth coolest February-April.

Precipitation Highlights. April precipitation in most areas east of the Mississippi River was below average. Wetness returned to the West Coast, as the Northwest climate region averaged much-above-normal precipitation.

• Many Mid-Atlantic states observed much-below-normal precipitation. Both Louisiana and South Carolina experienced their sixth driest April. It was also abnormally dry in Connecticut (eight), North Carolina (ninth), Virginia (ninth) and Maryland (tenth). Conversely, it was Oregon’s tenth-wettest April on record.

• The dryness in Michigan has persisted throughout 2010, becoming the second driest January-April period on record. The year-to-date period was also the seventh driest for Wisconsin and Kentucky and the eighth driest for Louisiana.

Other Highlights. According to the Rutgers Snow Lab, a NOAA-supported facility, the North American snow cover extent for the month was the lowest on record for April dating back to 1966. It was also the largest negative anomaly, meaning distance below long term average, on record for any month.

NCDC’s Climate Extremes Index (CEI) for January-April was about 6 percent higher than the historical average for that time period. The CEI measures the occurrence of several types of climate extremes (like record or near-record warmth, dry spells, or rainy periods). Factors contributing to this year’s value: a very large footprint (three times larger than average) of extreme wetness and twice the average area with warm minimum temperatures.

According to NOAA’s Storm Prediction Center, 195 tornadoes were reported in April. If the preliminary tornado count stands, it would be the eighth highest number of April tornadoes.

The most significant tornado of the month, which was rated EF-4 on the Enhanced Fujita scale, devastated areas near Yazoo City, Miss. According to a preliminary analysis by the National Weather Service, the tornado’s path was 149 miles long and stretched from extreme northeastern Louisiana to northeastern Mississippi. The damage path was up to 1¾ miles wide at points. The tornado claimed the lives of 10 people.

Drought coverage increased slightly during the month to a value near historical norms. The US Drought Monitor reported that 9% of the United States was affected by drought on 27 April.

NCDC’s preliminary reports, which assess the current state of the climate, are released soon after the end of each month. These analyses are based on preliminary data, which are subject to revision. Additional quality control is applied to the data when late reports are received several weeks after the end of the month and as increased scientific methods improve NCDC’s processing algorithms.