812
CXUS55 KRIW 012024
CLMP60

CLIMATE REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
212 PM MDT WED OCT 01 2025

...PRELIMINARY MONTHLY CLIMATE SUMMARY FOR LAKE YELLOWSTONE FOR THE
MONTH OF SEPTEMBER 2025...

...OFFICIAL CLIMATE DATA FOR THE MONTH OF SEPTEMBER 2025 WILL BE
AVAILABLE APPROXIMATELY IN 60 DAYS FROM THE NATIONAL CENTERS FOR
ENVIRONMENTAL INFORMATION (HTTP://WWW.NCDC.NOAA.GOV/CDO-
WEB/DATASETS). UNOFFICIAL ASOS DAILY SUMMARIES ARE AVAILABLE ON THE
INTERNET AT HTTP://WWW.WEATHER.GOV/CLIMATE/INDEX.PHP?WFO=RIW

...LAKE YELLOWSTONE WAS WARMER AND DRIER THAN NORMAL IN SEPTEMBER...

AVERAGE TEMPERATURE FOR LAKE YELLOWSTONE IN SEPTEMBER WAS 48.6
DEGREES WHICH IS 3.2 DEGREES ABOVE NORMAL. IT WAS THE 5TH WARMEST
SEPTEMBER SINCE RECORDS BEGAN IN 1998. THE WARMEST READING OF THE
MONTH WAS 78 DEGREES ON THE 3RD. THE HIGH OF 69 ON THE 20TH TIED
WITH 2012. THE COLDEST READING OF THE MONTH WAS 27 DEGREES ON THE
23RD.

TOTAL PRECIPITATION AT LAKE YELLOWSTONE WAS 1.46 INCHES...WHICH WAS
93 PERCENT OF NORMAL. THE WETTEST 24-HOUR PERIOD DURING THE MONTH
WAS THE 7TH WHEN 0.76 INCHES OF PRECIPITATION FELL. THIS BROKE THE
2002 RECORD OF 0.49. THE HIGHEST WIND GUST WAS 30 MPH FROM THE WEST
ON THE 7TH.

...THE LAKE YELLOWSTONE WY CLIMATE SUMMARY FOR THE MONTH OF
SEPTEMBER 2025...

CLIMATE NORMAL PERIOD: 1991 TO 2020
CLIMATE RECORD PERIOD: 1998 TO 2025

WEATHER         OBSERVED          NORMAL  DEPART   LAST YEAR`S
                VALUE   DATE(S)   VALUE   FROM     VALUE
                                          NORMAL
..............................................................
TEMPERATURE (F)
RECORD
 HIGH             83   09/07/2022
 LOW              13   09/24/2000
HIGHEST           78   09/03
LOWEST            27   09/23
AVG. MAXIMUM    64.6               60.5     4.1
AVG. MINIMUM    32.5               30.3     2.2
MEAN            48.5               45.4     3.1
DAYS MAX >= 90     0
DAYS MAX <= 32     0
DAYS MIN <= 32    16
DAYS MIN <= 0      0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM        4.09   2013
 MINIMUM        0.21   2018
TOTALS          1.46               1.57   -0.11     1.43
DAILY AVG.      0.05               0.05   -0.00
DAYS >= .01       11
DAYS >= .10        3
DAYS >= .50        1
DAYS >= 1.00       0
GREATEST
 24 HR. TOTAL   0.76   09/07 TO 09/07
 STORM TOTAL    0.76

DEGREE DAYS
HEATING TOTAL    484                588    -104
 SINCE 7/1      1000               1230    -230
COOLING TOTAL      0                  0       0
 SINCE 1/1         1                  0       1
..............................................................

WIND (MPH)
AVERAGE WIND SPEED              1.9
RESULTANT WIND SPEED/DIRECTION   0/080
HIGHEST WIND SPEED/DIRECTION    17/270    DATE  09/07
                                17/280          09/11
HIGHEST GUST SPEED/DIRECTION    30/270    DATE  09/07

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM
AVERAGE SKY COVER           0.00
NUMBER OF DAYS FAIR           28
NUMBER OF DAYS PC              0
NUMBER OF DAYS CLOUDY          0

AVERAGE RH (PERCENT)     63

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              1     MIXED PRECIP               0
HEAVY RAIN                1     RAIN                       1
LIGHT RAIN               11     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                       0     FOG W/VIS <= 1/4 MILE      0
HAZE                      0

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

LOOKING AHEAD TO OCTOBER 2025. THE AVERAGE HIGH TEMPERATURE ON THE
FIRST OF THE MONTH IS 53 DEGREES...AND THE AVERAGE LOW TEMPERATURE
IS 27 DEGREES. THE AVERAGE HIGH BY THE END OF THE MONTH IS 39
DEGREES AND THE AVERAGE LOW TEMPERATURE IS 17 DEGREES. THE AVERAGE
MONTHLY PRECIPITATION IS 1.85 INCHES.

$$