September 2017 Climate Summary for Northern and Eastern Maine

September Was the 3rd Warmest on Record!

...NORTHERN AND EASTERN MAINE SEPTEMBER 2017 MONTHLY NARRATIVE...

SEPTEMBER 2017 FINISHED WELL ABOVE AVERAGE IN TEMPERATURE AND MOSTLY
DRIER THAN NORMAL FOR RAINFALL.

AT MOST OF THE CLIMATE SITES ACROSS THE REGION, SEPTEMBER AVERAGED
BETWEEN 5 AND 6 DEGREES F ABOVE AVERAGE. INTERESTINGLY, THE RANKING
AT ALL OF OUR CLIMATE SITES WHICH INCLUDE CARIBOU...HOULTON...
MILLINOCKET AND BANGOR, WAS 3RD WARMEST, WITH SEPTEMBER 1999, 2015,
1961, AND 1934  OR A LITTLE WARMER DEPENDING ON WHAT
STATION THE COMPARISON IS MADE.

THE MONTH BEGAN ON A VERY COOL START, THEN TURNED PROGRESSIVELY MORE
ABOVE AVERAGE FURTHER INTO THE MONTH, THEN FINALLY ENDED ON A COOL
MORE FALL LIKE NOTE. WARM SPELLS INCLUDED THE 11TH THROUGH 17TH AND
THE 19TH THROUGH 27TH. THE 23RD THROUGH 26TH IN PARTICULAR DEFIED
NORMAL CLIMATOLOGY OF SHARPLY DECLINING AVERAGE TEMPERATURES WITH 4
STRAIGHT DAYS OF HIGH TEMPS WELL INTO THE 80S AND EVEN LOW 90S ON
THE 26TH AT SOME SITES INCLUDING MILLINOCKET AND AS FAR NORTH AS
HOULTON. MANY LOCATIONS EXPERIENCED THEIR WARMEST HIGH TEMPERATURES
SO LATE IN THE SEASON ON THE 25TH AND 26TH. INDEED, MONTHLY MAXIMUM
TEMPERATURES THIS MONTH WERE WARMER THAN LAST MONTHS MAXIMUM
TEMPERATURES WITH A GREATER NUMBER OF 80+ DEGREE HIGH TEMPS, BOTH
UNUSUAL FOR SEPTEMBER. A FEW LOCATIONS, SUCH AS CARIBOU, ALSO TIED
THE RECORD FOR THE GREATEST NUMBER OF 80+ DEGREE HIGH TEMPERATURE
DAYS FOR THE MONTH OF SEPTEMBER.

RAINFALL ACROSS THE REGION RANGED FROM 65 TO 100 PERCENT OF NORMAL,
WITH NORTHERN LOCATIONS GENERALLY RECEIVING MORE THAN DOWNEAST
AREAS. RAINFALL, HOWEVER, WAS VERY UNEVENLY DISTRIBUTED THROUGH THE
MONTH, WITH MOST RAIN FALLING BETWEEN THE 3RD AND 6TH WITH VERY
SCANTY AMOUNTS AFTERWARDS UNTIL THE 27TH ACROSS THE NORTH AND
THROUGH THE VERY END OF THE MONTH ELSEWHERE. CARIBOU WENT 17
STRAIGHT DAYS WITHOUT MEASURABLE RAINFALL BETWEEN THE 10TH AND
26TH, ENDING ON THE 27TH WHEN A LINE OF STRONG EVENING THUNDERSTORMS
ENDED THE RECORD SHATTERING LATE SEASON HEAT WAVE.

THE OFFICIAL OUTLOOK FOR THE MONTH OF OCTOBER FROM THE CLIMATE
PREDICTION CENTER FOR THE REGION IS TILTED TOWARD AN INCREASE
LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES.  THERE ARE NO STRONG
CLIMATE SIGNALS THAT WOULD POINT TOWARD AN UNUSUALLY WET OR DRY
OCTOBER.

AVERAGE HIGHS AT CARIBOU DROP FROM 59 DEGREES ON THE 1ST TO 46F BY
THE END OF THE MONTH.  AVERAGE LOWS DROP FROM 40F ON THE 1ST TO 30
BY THE END OF THE MONTH.  AT BANGOR, AVERAGE HIGHS FALL FROM 64F TO
52F, WHILE THE AVERAGE LOWS DROP FROM 42F TO 33F.

TROPICAL OR EX-TROPICAL SYSTEMS CAN OCCASIONALLY AFFECT THE REGION
WITH HEAVY RAINFALL DURING THE MONTH OF OCTOBER.  THUNDERSTORMS ARE
NOT UNHEARD OF IN OCTOBER, BUT ARE NOT A FREQUENT OCCURRENCE.  SNOW
IS POSSIBLE DURING THE MONTH, BUT IS VERY RARE THE FIRST HALF OF THE
MONTH. SNOW BECOMES MUCH MORE LIKELY LATE IN THE MONTH, ESPECIALLY
SO ACROSS FAR NORTHERN AREAS.  OVER 1 1/2 HOURS OF AVAILABLE
DAYLIGHT IS LOST DURING THE MONTH OF OCTOBER.