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000
CXUS55 KBOI 011832
CLMBOI

CLIMATE REPORT...CORRECTED TO ADD NARRATIVE
NATIONAL WEATHER SERVICE BOISE ID
1133 AM MDT SUN OCT 01 2023

SEPTEMBER WAS SLIGHTLY WARMER THAN NORMAL. TEMPERATURES AVERAGED
ABOVE NORMAL ON 20 DAYS.

PRECIPITATION WAS CLOSE TO NORMAL. MEASURABLE RAIN FELL ON ONLY 5
DAYS.

ON THE 1ST AND 2ND, HIGHS WERE IN THE 80S UNDER SOUTHERLY FLOW ON
THE EASTERN FLANK OF A LOW PRESSURE TROUGH OVER THE WEST COAST.

THE TROUGH MOVED INLAND ON THE 3RD, BRINGING SHOWERS AND COOLING
TEMPERATURES BY AROUND 10 DEGREES.

FOLLOWING THE TROUGH, HIGHS WERE BACK IN THE MID 80S ON THE 5TH AND
REACHED 90 DEGREES ON THE 6TH UNDER SOUTHWESTERLY FLOW FROM
CALIFORNIA. THAT AFTERNOON, AN ISOLATED THUNDERSTORM DEPOSITED .03
INCH OF RAIN AT THE AIRPORT, FOLLOWING A WIND GUST OF 40 MPH FROM
THE SOUTHWEST.

A WEAK TROUGH APPROACHING FROM THE WEST ON THE 7TH SET OFF ISOLATED
THUNDERSTORMS, BUT ONLY A TRACE OF RAIN FELL AT THE AIRPORT.

NO MEASURABLE RAIN FELL AGAIN UNTIL THE 22ND.

HIGH PRESSURE ALOFT OVER THE WESTERN U.S. KEPT PACIFIC WEATHER
SYSTEMS NORTH OF OUR AREA FROM THE 8TH THROUGH THE 12TH.

A WEAK COLD FRONT ASSOCIATED WITH ONE OF THESE SYSTEMS CROSSED OUR
AREA ON THE 13TH. IT COOLED HIGHS INTO THE LOWER 80S ON THE 13TH AND
14TH, COMPARED TO THE LOWER 90S FROM THE 9TH THROUGH THE 11TH AND
UPPER 80S ON THE 12TH.

A NEW HIGH PRESSURE RIDGE WAS ALREADY BUILDING INLAND ON THE 14TH,
AND DURING THE AFTERNOON OF THE 16TH THE TEMPERATURE HIT 93 AT THE
AIRPORT. THAT TIED THE RECORD FOR THE DATE LAST OBSERVED IN 2014.

BY THE 18TH, A LARGE HIGH PRESSURE RIDGE HAD BECOME ESTABLISHED
BETWEEN ALASKA AND HAWAII. FOR OUR AREA, THE RESULTING PATTERN
CHANGE STARTED A COOLING TREND UNDER NORTHWEST FLOW ALOFT.

THE FIRST COLD FRONT CROSSED THE BOISE AREA ON THE 19TH, LOWERING
HIGHS FROM THE 80S TO THE 70S.

ON THE 20TH, A SECOND COLD FRONT PASSED. THE COLD UPPER LEVEL TROUGH
BEHIND THE FRONT PREVENTED THE TEMPERATURE FROM RISING ABOVE 66
DEGREES, AFTER A MORNING LOW OF 43.

STARTING ON THE 23RD, A HIGH PRESSURE RIDGE BEGAN TO BUILD OVER THE
ROCKIES, AND TEMPERATURES WERE ABOVE NORMAL AGAIN FROM THE 24TH
THROUGH THE 26TH.

MEANWHILE ON THE 24TH, A DEEP TROUGH WAS FORMING OFF THE NORTHWEST
COAST.

FOLLOWING AN AFTERNOON COLD FRONT ON THE 26TH, THE TROUGH MOVED
INLAND ON THE 27TH, LOWERING TEMPERATURES TO NEAR NORMAL. LIGHT
PRECIPITATION FELL AT MCCALL, BUT BOISE STAYED DRY.

THAT TROUGH WEAKENED AND WAS REPLACED BY A TROUGH WHICH DEEPENED
SOUTHWARD OVER THE WEST COAST ON THE 29TH. IT PUSHED INLAND ON THE
30TH, BRINGING A QUARTER INCH OF RAIN. THE HIGH OF 57 WAS THE
COOLEST MAX TEMPERATURE SINCE THE 53 ON APRIL 21ST.

...................................

...THE BOISE ID CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2023...

CLIMATE NORMAL PERIOD 1991 TO 2020
CLIMATE RECORD PERIOD 1875 TO 2023

WEATHER         OBSERVED          NORMAL  DEPART   LAST YEAR`S
                VALUE   DATE(S)   VALUE   FROM     VALUE
                                          NORMAL
..............................................................
TEMPERATURE (F)
HIGHEST           93   09/11
                       09/16
LOWEST            42   09/28
AVG. MAXIMUM    81.0               80.0     1.0
AVG. MINIMUM    55.4               52.6     2.8
MEAN            68.2               66.3     1.9
DAYS MAX >= 90     5
DAYS MAX <= 32     0
DAYS MIN <= 32     0
DAYS MIN <= 0      0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM        2.93   1986
TOTALS          0.45               0.43    0.02
DAYS >= .01        6
DAYS >= .10        2
DAYS >= .50        0
DAYS >= 1.00       0
GREATEST
 24 HR. TOTAL   0.23   09/30 TO 09/30

DEGREE DAYS
HEATING TOTAL     49                 80     -31       13
 SINCE 7/1        49                 94     -45
COOLING TOTAL    156                119      37      206
 SINCE 1/1      1322               1034     288
..............................................................

WIND (MPH)
AVERAGE WIND SPEED              6.8
HIGHEST WIND SPEED/DIRECTION    28/240    DATE  09/06
HIGHEST GUST SPEED/DIRECTION    40/220    DATE  09/06

AVERAGE RH (PERCENT)     41


-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.

$$