Monthly Report Summary Information

National Summary Information - May 2016

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Significant climate events for May 2016

Near-average May closes out warm, wet spring for contiguous US

Alaska shatters heat records for spring and year to date

The Spring temperature for the contiguous U.S. was the 6^th warmest at 53.7°F, or 2.8°F above the 20^th century average. The May temperature was 60.3°F, 0.1°F above the 20^th century average and near the middle of the 122-year record. The Spring precipitation total for the contiguous U.S. was 9.03 inches, 1.09 inches above the 20^th century average, the 18^th wettest on record. The May precipitation total was near average for the month at 3.04 inches.

This analysis of U.S. temperature and precipitation is based on data back to January 1895, resulting in 122 years of data.

Supplemental May 2016 Information

• Recurrent tidal flooding

U.S. climate highlights: Spring (March - May)

Temperature

• Despite a near-average May, warmth in March and April fueled the warmest spring in the contiguous U.S. since the record-breaking spring of 2012. As has been the case for much of this decade, overnight temperatures were generally relatively higher than afternoon temperatures when compared to average.
• Every state had a spring temperature that was above average. Fifteen states observed much-above-average temperatures. The highest spring temperatures, relative to history, occurred in the Northwest and much of the northern tier. Washington had its second warmest spring on record, while Oregon had its third warmest.
• For the first time in Alaska's modern climate record, its average spring temperature hit 32.0°F. This was easily Alaska's warmest spring on record, eclipsing the previous record set in 1998 by 2.0°F.

Precipitation

Spring 2016 Temperature Departure from Average
(top) and Precipitation Percent of Average (bottom)

• When averaged across the contiguous U.S., the national precipitation total of 9.03 inches was 1.09 inches above the 20th century average and registered as the nation's 18th wettest spring in the 122-year record.
• Above-average spring precipitation fell across most of the area between the Mississippi River and the Pacific Coast. Nebraska, Wyoming, Louisiana and Texas saw much above-average precipitation. Alaska was also wetter than average for the season. Dryness prevailed in the Northeast, where New York and Connecticut observed much drier-than- average spring precipitation totals.
• The U.S. Climate Extremes Index (USCEI) for the spring was 20 percent above average and the 22^nd highest value on record. On the national scale, extremes in warm maximum and minimum temperature, one-day precipitation totals and the spatial extent of wetness were much above average. The USCEI is an index that tracks extremes (falling in the upper or lower 10 percent of the record) in temperature, precipitation and drought across the contiguous U.S.

U.S. climate highlights: May

Temperature

• The average May temperature for the contiguous U.S. was 60.3°F, just 0.1°F warmer than the 20th century average and near the middle of the 122-year record.
• Below-average May temperatures stretched from a slice of the Mid-Atlantic to a broad region of the Southern Plains and Southern Rockies. Warmer-than-average conditions prevailed across the nation's northern tier. A pocket of much-above-average temperatures occurred in the Pacific Northwest.
• Alaska had its second warmest May on record with a statewide temperature of 44.0°F, 6.0°F above average and 1.0°F shy of its May record set last year.

Precipitation

Spring 2016 Temperature Departure from Average
(top) and Precipitation Percent of Average (bottom)

• Precipitation, averaged across the contiguous U.S. was 3.04 inches, which is 0.13 inch above the 20th century average.
• Above-average precipitation was observed in parts of the Rockies, Plains, Southwest and Atlantic Coast, where Delaware and Virginia each observed their fifth wettest May on record. Below-average precipitation was focused across the Northeast, Southeast, and parts of the Midwest and Northwest.
• In central and eastern Texas, torrential late May rains, on top of generally wet conditions from earlier in the spring, led to severe flooding that lasted into early June.
• According to the May 31 U.S. Drought Monitor report, 12.7 percent of the contiguous U.S. was in drought, down considerably from 15.4 percent in late April. Drought conditions improved or were eliminated in parts of the Great Basin and Plains. Drought also improved somewhat in northern California and Nevada but persisted in the southern half of California. Drought developed in parts of the Southeast and southern Appalachians. Outside of the contiguous U.S., there was little drought relief for Hawai'i during May; drought generally persisted, although there was a modest contraction on the Big Island. Drought conditions improved across Puerto Rico.

U.S. climate highlights: year-to-date (January-May)

Temperature

• The average year-to-date temperature for the contiguous U.S. was 46.6°F, 3.2°F above the 20^th century average and the fourth warmest of the 122-year record.
• Every state was warmer than average for the period. Twenty-nine states across the West, Great Plains, Midwest and Northeast were much warmer than average, while much of the nation's southern tier experienced above-average temperatures.
• As was the case through April, Alaska's year-to-date average temperature was record warm. This year's January-May value of 26.1°F was 10.3°F above the 1925-2000 average and 2.4°F higher than the previous record of 23.7°F set in 1981. The last three January-May periods have been three of the four warmest on record for Alaska.

Precipitation

Jan-May 2016 Temperature Departure from Average
(top) and Precipitation Percent of Average (bottom)

• Above-average precipitation prevailed for the contiguous U.S. as the average year-to-date precipitation was 13.1 inches, 0.7 inch more than the 20^th century average.
• Above-average precipitation occurred in the Central Plains, Northern High Plains and Rockies, and parts of Arkansas, Louisiana and Texas. Below-average precipitation was observed for much of the Southwest, Midwest, Southeast and Northeast.
• At the state level, only one state experienced a much-above year-to-date precipitation total: Nebraska's five-month total of 12.03 inches was its seventh wettest start to the year. No state had much-below average precipitation.

Extremes

• The U.S. Climate Extremes Index (USCEI) for the year-to-date was 40 percent above average and the 16^th highest value on record. On the national scale, extremes in warm maximum and minimum temperature and the spatial extent of wetness were much above average. The USCEI is an index that tracks extremes (falling in the upper or lower 10 percent of the record) in temperature, precipitation and drought across the contiguous U.S.

For extended analysis of regional temperature and precipitation patterns, as well as extreme events, please see our full report that will be released on June 13^th.