Earliest Measureable Snowfall in 17 Years at Duluth

September 30 Update: Through yesterday, the monthly temperature at Duluth was 0.5° above average. Today's average of +5° (through 5 pm local time) will raise the monthly average by another 0.1-0.2°.

Original post:
The National Service reports on the early snowfall Friday at Duluth, Minnesota:

0.1 inches of snow fell in the late evening hours of Friday, September 21, 2012 at Duluth. This is the earliest snowfall of the season in 17 years. On September 21, 1995, 0.1 of snow fell on that day also.

International Falls reported a trace of snow. The record 24-hour snowfall for September at Duluth was 2.4" on the 18th in 1991.

Through the first 22 days, September's temperature has averaged 1.0° above climatology at Duluth.

Attention Climate Conspiracists: NOAA Adjustments Show Summer 2012 3rd Hottest on Record

Attention climate conspiracists (lookin' at you, Tom Nelson-bot): The NOAA/National Climatic Data Center (NCDC) analysis for August 2012 is in, and it shows that Summer 2012 was tied for the 3rd hottest on record in the contiguous 48 states of the U.S. That's right, analysis of the raw National Weather Service (NWS) data and even the preliminary August adjustments from NCDC showed the summer would be at least tied with 2011 for second place, but the final analysis posted today lowered the August average by 0.1° to a tie with 2006 for 3rd place.

Rather than being 10th warmest, as the preliminary data indicated, August came in at 16th warmest with an average of 74.4°, nearly half a degree below the raw estimate of 74.8°. This is a pattern that CapitalClimate has seen since we started tracking weekly averages at the beginning of summer: The weekly raw averages from 200+ NWS stations are adjusted downward by NCDC, and the monthly averages end up being even more conservative.

From the NCDC summary:

The average temperature for the contiguous U.S. during August was 74.4°F, 1.6°F above the 20th century average, marking the 16th warmest August in a period of record that dates back to 1895.

Higher-than-average temperatures occurred across much of the West, where Nevada tied August 1934 as its warmest August on record, with a statewide temperature 4.0°F above average. Six additional states across the region had August temperatures ranking among their ten warmest. Much of the Northeast was also warmer than average, where five states from Maine to Delaware had monthly temperatures among the ten warmest.

Much of the Central U.S. had near to below average August temperatures, with lower-than-average temperatures across the Ohio Valley and the Southeast.

The warmer than average August, in combination with the hottest July and a warmer than average June, contributed to the third hottest summer on record for the contiguous United States. The summer season’s nationally-averaged temperature was 74.4°F, 2.3°F above the 20th century average. Only the summers of 2011 (74.5°F) and 1936 (74.6°F) had higher temperatures for the Lower 48.

The summer season was warmer than average for a large portion of contiguous United States, with the exception of the Southeast and parts of the Northwest. Sixteen states across the West, Plains, and Upper Midwest had summer temperatures among their ten warmest. Colorado and Wyoming each had their record hottest summer, with seasonal temperatures 4.4°F and 4.9°F above average, respectively. Much of the Northeast was warmer than average, where seven states from New Hampshire to Maryland had a top ten warm summer.

Images (click to enlarge):
- Hottest U.S. average summer temperatures, CapitalClimate chart from NCDC data
- Statewide average temperature ranks, Summer 2012, from NCDC
- U.S. average temperature departures from normal, August 2012, from NOAA/HPRCC
- Statewide average temperature ranks, August 2012, from NCDC

Only 4% of U.S. Cooler Than Average as Fall Begins With 39th Consecutive Warm Week

CapitalClimate analysis of temperature data from 215 National Weather Service (NWS) stations shows that the week ending September 8 was 4.0° above average in the contiguous 48 states of the U.S. Just 9 locations, or 4% of the total, were cooler than normal. This is the 39th consecutive week with above-average temperatures. Except for one week in early December, every week in the past winter, spring, and summer has now been warmer than normal.

Here is the complete list of NWS locations which were cooler than average for the week (alphabetically by state):

State  City      ID    Departure
CA SAN FRANCISCO SFO    -3
CA STOCKTON      SCK    -1
FL KEY WEST      EYW    -1
ID POCATELLO     PIH    -1
MT BUTTE         BTM    -2
MT HAVRE         HVR    -2
ND JAMESTOWN     JMS    -1
ND WILLISTON     ISN    -1
SD ABERDEEN      ABR    -1 

38th Consecutive Warm Week Concludes Warm August, Summer, Last 12 Months

September 4 Update: The preliminary NCDC adjusted average for August is 1.2° above normal. This keeps summer 2012 on track for the second hottest on record in the U.S. All 9 regions except for East North-Central were above average in August.

Original post:
CapitalClimate analysis of preliminary National Weather Service data shows that the week ending September 1 was the 38th consecutive week of above-average temperatures in the contiguous 48 states of the U.S. The unadjusted average of temperatures from 215 NWS stations was 3.9° above climatology, up significantly from the geographically adjusted 0.8° the previous week.

The very warm final week of August capped a month in which the overall preliminary temperature was 1.3° above average. If this holds through the National Climatic Data Center (NCDC) analysis, the monthly average of 74.8° would be tied for the 10th warmest August, just behind 2010. Combined with the record hottest July and warm June, the summer estimated average of 74.5° would be tied with 2011 as the second hottest on record, 0.1° behind 1936.

For the year to date as well as the past 12 months dating back to September 2011, average temperatures have been warmer than normal nearly everywhere in the country except the immediate Pacific Northwest coast. The warmest temperatures relative to average have been in the upper Midwest and northern Plains.

Images (click to enlarge):
- Weekly average U.S. temperature departures from normal, weeks ending June 4, 2011 (20110604) through September 1, 2012 (20120901); CapitalClimate chart from NOAA/NCDC data
- Weekly average NWS station temperature departures from normal, week ending September 1, 2012; stations listed alphabetically by state and 3-character station identifier; CapitalClimate chart from NWS data
- Warmest U.S. summer average temperatures (2012 estimated); CapitalClimate chart from NCDC data
- Average U.S. temperature departure from normal for September 2011 through August 2012 from High Plains Regional Climate Center

Wettest UK Summer in a Century

The UK Met Office reports that Summer 2012 is likely to be the wettest since 1912 and the second wettest on record:

Figures up to the 29 August show that 366.8 mm of rain fell across the UK. It is not expected that rainfall this summer will exceed the 384.4 mm of rain seen in the summer of 1912, which is the wettest.

These latest figures follow a record wet April, and an April to June period that was also the wettest recorded in the UK.

August 2012 looks set to be the driest and sunniest of the three summer months across the UK with 105.5 mm of rain to the 29 August and 140 hours of sunshine up to 28 August. The mean temperature for August was 15.7 °C, in a month that also saw the hottest day of the year so far, reaching 32.4 °C at Cavendish, Suffolk on the 18th.

Summer 2012 is also likely to be one of the dullest summers on record with just 399 hours of sunshine up to 28 August. This makes it the dullest summer since 1980 when the UK saw only 396 hours of sunshine.

To complete the disappointing picture, it has also been a relatively cool summer with a mean temperature of 14.0 °C, some 0.4 °C below the long term average. Despite this it was a little warmer than the summer of 2011 which saw a mean temperature of only 13.7 °C.

Unsettled weather has never been far from the UK during the past three months. Movements in the track of the jet stream, a narrow band of fast flowing westerly winds high in the atmosphere, have contributed to the weather we have seen. This summer has seen periods of heavy and prolonged rain, as well as short but exceptionally heavy thundery downpours and only brief warm sunny spells.

Looking at the individual countries of the UK, it is set to be the second wettest summer on record in England, third wettest in Wales, ninth in Northern Ireland, and the seventh wettest in Scotland. For sunshine it is expected to be the second dullest summer in England and Wales, 12th in Northern Ireland and 16th dullest in Scotland.

Image (click to enlarge): UK precipitation (mm/day), June 1-August 20, 2012, from NOAA/ESRL

Warm U.S. Year Rolls Through 37th Consecutive Week

The record warm year of 2012 continued through the 37th consecutive week of above-average temperatures in the U.S., according to preliminary analysis from the National Climatic Data Center for August 19-25. The national average of 0.8° above normal was down slightly from 1.2° the previous week. The month-to-date average was 1.3° warmer than normal with one week left in August. Once again, only 3 of the 9 regions were cooler than average (East North-Central, Central, and Southeast).

Given the remarkable week-to-week consistency of the warm temperatures, it's not surprising that nearly the entire country is averaging above normal for the year to date. Only the Pacific Northwest and parts of northern California have been cooler than average in the interval from January 1 through today.

Images (click to enlarge):
- Weekly average U.S. temperature departures from normal, weeks ending June 4, 2011 (20110604) through August 25, 2012 (20120825); CapitalClimate chart from NOAA/NCDC data
- Average U.S. temperature departure from normal for August 1-28, 2012 from High Plains Regional Climate Center
- Average U.S. temperature departure from normal for January 1-August 28, 2012 from High Plains Regional Climate Center

Despite Cooling Midwest, U.S. Has 36th Consecutive Warm Week

The preliminary National Climatic Data Center analysis shows that the U.S. national average temperature was 1.2° above normal in the week ending August 18, with the month-to-date average 1.5° above. As was the case in the previous week, the East North-Central region was below average, and the cooler temperatures spread into the Central and West North-Central regions. However, the other 6 regions remained warmer than average.

Images (click to enlarge):
- Weekly average U.S. temperature departures from normal, weeks ending June 4, 2011 (20110604) through August 18, 2012 (20120818); CapitalClimate chart from NOAA/NCDC data
- Average U.S. temperature departure from normal for August 12-18, 2012 from High Plains Regional Climate Center