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Record Rainfall, Widespread Warmth Highlight September Climate Report (INTERACTIVE)

By Nick Wiltgen
Published: October 23, 2013

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Source: National Climatic Data Center
Above: Our interactive map shows the temperature and precipitation rankings by state compared to average for September 2013. Click the Previous and Next buttons to step through the maps. Hover over each state for more detailed information.

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September was the sixth warmest and 12th wettest of the past 119 years nationally, according to the National Climatic Data Center (NCDC), which releases its State of the Climate report every month.

The federal government’s climate agency released its analysis of September temperature and precipitation data for the U.S. on Monday, more than a week later than usual, after the partial government shutdown prevented the information from being released on time.

Background

Temperatures Compared to Average Red shades indicate warmer-than-average states; blue shades, cooler-than-average.

Temperatures Compared to Average

Temperatures Compared to Average

Temperatures Compared to Average

Widespread Warmth

The warmth was widespread, with 26 of the contiguous 48 states logging above-average September temperatures. Most of these states were in the western two-thirds of the country. Seven states – Idaho, Montana, Wyoming, Colorado, North and South Dakota, and Nebraska – registered a top-10 warmest September on record.

Only four states – New York, Pennsylvania, New Jersey, and Maryland – were labeled cooler than average. The Empire State had the coolest state-by-state ranking, logging its 33rd coolest September of the past 119 years.

The NCDC defines above-average temperatures and precipitation as readings placing in the top one-third of the historical record for a given area, and below-average temperatures and precipitation as those placing in the bottom one-third.

Background

Precipitation Compared to Average Green shades indicate wetter-than-average states; yellow shades, drier-than-average.

Precipitation Compared to Average

Precipitation Compared to Average

Precipitation Compared to Average

Record Rainfall

September’s historic Colorado flood disaster was reflected in the official data, with the Centennial State logging by far its wettest September on record. The statewide average of 4.09 inches was 40 percent wetter than Colorado’s previous September record of 2.93 inches set in 1961.

In fact, only two other months in Colorado recordkeeping have been wetter – April 1900 (5.51 inches) and April 1942 (4.20 inches).

The state record was driven by extreme rainfall in mid-September, particularly over the northern part of Colorado's Front Range. Some locations near Boulder picked up well over a foot of rain in just five days, leading to destructive flash floods.

An unusually early bout of heavy rainfall also pushed Washington and Oregon to their wettest Septembers on record. Oregon crushed its 1986 record by a margin of 30 percent, while Washington was about 4 percent wetter than its previous 1959 record.

Seattle received 6.17 inches of rain on the month, eclipsing a 35-year-old record. It was also the wettest September on record in Portland, Ore., where 5.62 inches of rain last month crushed the old September record of 4.30 inches set in 1986.

Such heavy rainfall is more typical of November, December, and January in the Pacific Northwest.

(MORE: Record Rainstorms Pound Northwest)

September also placed among the ten wettest on record in Idaho, Nevada, Utah, Montana, Wyoming, New Mexico, and North Dakota. In all, 19 states were wetter than average.

Drier-than-average conditions dominated from the upper Mississippi Valley to the Mid-Atlantic and parts of the Southeast. It was Maryland’s sixth-driest September and Delaware’s ninth driest, while 13 other states logged below-average precipitation.

For Georgia and South Carolina, September was the first drier-than-average month since January 2013.

Who Was Normal?

The NCDC considers temperatures and precipitation in the middle third of the historical range to be “near normal.” Eight states managed to be near normal in both temperatures and precipitation for September: Indiana, Ohio, Kentucky, Tennessee, Alabama, Vermont, Massachusetts and Connecticut.

Of these, Massachusetts was closest to the historical average, ranking 58th coolest and 62nd wettest; a ranking of 60th would be exactly in the middle of the historical record. Ohio was not far behind in normalcy, placing 53rd coolest and 57th wettest for the month.

How Are We Doing This Year?

For the first nine months of 2013, here’s how the national climate is doing:

  • Temperatures: 28th warmest on record nationally.
  • California has its ninth warmest year to date, but no other states are top-ten warm or cold at this point.
  • Precipitation: 11th wettest on record nationally. It’s the wettest year to date in Michigan, while North Dakota, Tennessee, Alabama, Georgia, South Carolina, and Virginia are all top 10 wettest.
  • It’s the driest year to date in California, but only two other states (Idaho and Nevada) are drier than average for 2013 through the end of September. California is running more than an inch behind the previous record-dry pace of 6.93 inches from 1898.

MORE: Ten Stunning September Sunsets

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Sunset at the Humber Bridge from the South, East Riding of Yorkshire. Image credit: VisitEngland/Iain Lewis

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