Weather Records Fell Like Autumn Leaves in October
The following is a Public Information Statement issued by the
National Weather Service, Great Falls MT
1130 AM MDT Mon Oct 26 2020:
There have been records set in many categories including warmest
and coolest maximum and minimum temperatures, winds, precipitation and
snowfall, snow on the ground and pressure values. Several coldest
so early in the season records were also set. It is also notable that
the heavy snow of late October came on the heels of an extended dry
period across the region.
Of note for the state, there has been a wide range of temperatures
for the month. A station at Little Bighorn recorded 90F on the
sixth, while values of -29F occurred at Potomac and Ringling on the
25th and 26th. This 119F range is the second largest for October,
second only to 1935 when a high of 91F (Haugen) and low of -30F
(Summit/Marias Pass) resulted in a range of 121F.
Temperature...
Record type Location New Record Old Rec Yr Set
Oct 4....High Max Bozeman Apt 82 Tied 82 1970
High Max Helena 84 82 1970
Oct 6....High Min Choteau 55 52 1971
High Min Stanford 52 51 2006
High Max Bozeman Apt 82 Tied 82 1960
High Max Helena 84 Tied 84 1960
Oct 7....High Max Bozeman Apt 80 Tied 80 1980
High Max Helena 80 Tied 80 1889
Oct 8....High Max Helena 82 Tied 82 1910
Oct 18...Low Max Bozeman Apt 32 33 1949
Low Max Cut Bank 20 Tied 20 1949
Tied for third earliest 20F or cooler max
temp
Oct 22...Low Max Bozeman Apt 27 34 1961
Low Max Cut Bank 25 26 1957
Low Max Dillon 30 34 1961
Low Max Great Falls 20 28 1957
Low Max Havre 22 28 1893
Low Max Lewistown 20 24 2002
Low Min Bozeman Apt 15 16 1961
Low Min Dillon 13 15 1981
Low Min Great Falls 5 8 1917
Low Min Havre 3 8 1881
Oct 23...Low Min Bozeman MSU 8 10 1919
Low Min Cut Bank 5 6 2012
Low Min Dillon 7 12 1984
Low Min Great Falls 3 10 1957
Low Min Havre -5 8 1919
Low Min Fresno Reservoir and north of Chinook
-11
This is the eighth earliest of record for
a low of -10F or cooler in MT (since 1892).
Average for this event is November 13.
Low Max Bozeman Apt 28 30 1957
Low Max Cut Bank 16 17 1957
Low Max Great Falls 16 21 1957
Third earliest 20F or cooler max temp
Oct 24...Low Min Bozeman Apt 4 6 1975
Low Min Cut Bank -10 -4 1919
Earliest of record -10F or cooler min temp.
Old record was October 25 1919.
Low Min Dillon 5 14 2002
Low Min Lewistown -4 -1 1919
Low Max Bozeman Apt 23 31 1975
Low Max Cut Bank 14 18 1919
Low Max Dillon 24 31 1997
Low Max Lewistown 20 21 1919
The high temperature of 15 at Great Falls on the 24th did
not set a new record, as it was 14F for a high temperature
in 1919. It did tie for the earliest high temperature of
15F or cooler.
Oct 25...Low Min Bozeman Apt -14 9 1961
Earliest of record -10F or cooler min temp
Low Min Dillon -6 11 2002
Low Min Helena -4 0 1919
Second earliest subzero temp of record
Low Min Lewistown -6 -1 1919
Low Min Ringling -25
Previous record for this date in MT was
-21 at Shelby in 1919. This was the third
earliest that a -20F or colder temperature
was recorded in MT. The earliest was Oct 21
2009 at Placer Basin SNOTEL and the second
was at Babb on Oct 24, 1919. The average
for this event is November 24. Potomac
fell to -29 this morning.
Low Max Bozeman Apt 13 29 1969
This high temperature was the earliest in
the season for a maximum temperature of 15F
or colder. The record was October 29, 2019.
Low Max Bozeman MSU 15 22 1969
Low Max Dillon 13 28 1939
This high temperature was the earliest in
the season for a maximum temperature of 15F
or colder. The record was October 29, 2019.
Low Max Great Falls 14 17 1919
Low Max Helena 14 20 1919
This high temperature was the earliest in
the season for a maximum temperature of 15F
or colder. The record was October 27, 1925.
Low Max Lewistown 10 21 2012
This high temperature was the earliest in
the season for a maximum temperature of 15F
or colder. The record was October 28, 1971
and 1991. It was also the earliest for a
high temperature of 10F or colder. The
record was October 28, 1991.
Low Max W Yellowston 21 26 1975
Oct 26...Low Min Bozeman Apt -14 11 2002
All-time coldest for October. Previous was
-14F Oct 29 and 30, 2019.
Low Min Dillon -9 14 2011
Low Min Havre -3 3 1919
Low Min Helena -6 6 1919
Second earliest subzero temp of record
Low Min Lewistown -5 1 1923
Low Min Ringling -29
Previous record for this date in MT was
-16 at Wibaux in 1919. This tied for the
second coldest temperature recorded in MT
in October, and the coldest since -30
occurred at Summit/Marias Pass Oct 31 1935.
This would be the third coldest temp observed
in the lower 48 states in October. The
coldest is -33F at Soda Butte, WY on Oct 29
1917.
Low Min W Yellowstn -22 -4 1975
This value ties the all-time lowest October
temperature at West Yellowstone. The record
is -22F on October 22, 1923.
Wind...
Oct 10...High Pk Gust Bozeman 42 mph 37 1995
High Pk Gust Dillon 53 mph 45 2007
Oct 12...High Pk Gust Bozeman 49 mph 40 1980
High Pk Gust Dillon 46 mph 37 1980
High Pk Gust Helena 57 mph 45 2007
High Day Avg Bozeman 17.7 mph 12.0 1954
Seventh highest daily average for October
and highest in October since 2017.
Oct 13...High Pk Gust Dillon 59 mph 52 1971
Third highest gust of record for October.
Winds 700 mb Great Falls 76 kts at 6 pm
Second highest winds at 700 mb for October.
Winds 200 mb Great Falls 162 kts 6 pm 140 kts
Highest winds at 200 mb for October. Old
record is 140 kts Oct 31, 1994. Highest
for any time of year is 164 kts Jan 16 2011
and Jul 31 1961.
Oct 14...High Pk Gust Helena 57 mph 40 1991
High Pk Gust Lewistown 49 mph Tied 49 2016
High Day Avg Helena 18.4 mph 17.0 1991
Precipitation/Snow...
Oct 17...High Day Pcp Helena 0.63 in 0.53 1916
High Day Snw Great Falls 4.2 in 1.7 1961
High Day Snw Helena 6.6 in 5.0 1866
Oct 18...High Day Snw Great Falls 8.2 in 3.4 1949
This was also the greatest for any
calendar day in October. Previous record
was 6.6 inches on Oct 13, 1975.
High Day Pcp Great Falls 0.69 in 0.43 1979
Oct 17-18 2-day snow Great Falls 12.4 in 8.3 1957
Highest for any two-day period in Oct.
Seventeenth highest overall.
Oct 21...High Day Snw Havre 4.4 in 1.7 1961
Oct 22...High Day Snw Bozeman MSU 5.6 in 5.0 1975
Oct 23...High Day Snw Great Falls 4.0 in 2.8 1954
High Day Snw Helena 8.7 in 3.6 1919
Oct 24...High Day Snw Bozeman MSU 7.0 in 3.6 1997
High Day Snw Great Falls 7.0 in 3.1 1984
High Day Snw Havre 1.6 in Tied 1.6 1898
High Day Snw Helena 8.9 in 6.8 1969
Oct 23-24 24-hr snow Helena 17.6 in 14.0 1891
Highest 2-day total for October, too.
This is the 5th highest 2-day total for
any time.
October..High snowfall Great Falls 28.0 in 18.5 1925
Eighth snowiest any month of record.
High snowfall Bynum 4SSE 33.3 in 16.6 1975
High snowfall Choteau 24.4 in 21.0 1975
Seventh highest for any month.
High snowfall Stanford 21.0 in Tied 21.0 1975
High snowfall Loma 20.7 in 11.0 1984
High snowfall Cut Bank 20.9 in 17.5 1934
High snowfall Fort Benton 17.3 in 13.0 1951
The 8-day period from October 17-24 produced 26.8-inches of snow at
Great Falls. This is the snowiest 8-day period on which snow fell
every day. The snowiest 8-day period was Apr 23-30, 2009 when 28.5-
inches of snow fell on 7 of the days.
Areas in south and west Helena reported 20+ inches in the storm
from October 23-24. This was one of the heaviest snows in the Helena
area since the 1960s.
Pressure
Oct 24...High daily Bozeman 1040.3 mb 1039.3 2003
Sixth highest value for October.
High daily Dillon 1036.9 mb 1034.8 1965
High daily Great Falls 1042.8 mb 1038.1 1969
Second highest value for October.
High daily Havre 1041.0 mb 1036.0 1969
Third highest value for October.
High daily Helena 1042.5 mb 1038.0 2003
Second highest value for October.
Days with measurable snow
Great Falls recorded 9-days, which ties the record last set in 1984.
Days with 3-inches or more of snow
Great Falls recorded 4-days, which set a new record. The old record
was 3-days in 1975.
Snow on ground
Great Falls had 10-inches on the ground on the 19th. This exceeded
the previous record depth for October of 7-inches set in 2019.
Previously, the earliest date with 10-inches on the ground was
November 9, 2012. Average for this event is January 7, with it not
occurring in 18 of the last 30 years.
Helena measured 11-inches on the ground on the 24th. This exceeded
the previous record depth for October of 10-inches in 1925. The
earliest for this event was September 28, 1965. It has only occurred
in seven of the last 30 years.
Freeze-free period
Since the first freezing temperature at Great Falls on September 8,
the next freezing temperature was on October 13. The freezing
temperature on September 8 was their sixth earliest of record and
gave a freeze-free season of 107 days...the 9th shortest of record.
For first freezes much earlier than the average - such as this
year, it is not uncommon for the next to be closer to, and after
the seasonal average. The 1981-2010 seasonal average at Great Falls
is September 20. Of the 28-years in which freezing temps occurred
on or before September 15 at Great Falls, the average date for the
next freezing temp is 16-days later. This year, the second freeze
date on Oct 13 was 35-days later. This is the second longest of
record between the first and next freezes with the longest being a
46-day period between the first and subsequent freezing temps in
1962. Then, the first freeze was September 7 and the next was
October 23. The third longest such stretch was 33-days in 1956.
Even in the earliest freeze at GTF (Aug 22, 1992), there were 4-
days of freezing mins, with the next freezing min on Sep 6.
Extended dryness before the snow...
Dillon...
A 315-day period with no more than 6-inches of accumulated
precipitation ended on October 10. This was the longest such period
since a 331-day period ending April 14, 2013. The record is 408-days
ending January 1967.
Great Falls...
A 36-day period of no more than a trace of precipitation occurred
between September 8 and October 13. This is the 12th longest with
no more than a trace and longest since 2012. The record is 62-days.
Also, a 98-day period of no more than one-inch accumulated
precipitation occurred between July 11 and October 16. This is the
26th longest of no more than one-inch of precipitation and longest
since 2019. The record is 188-days.
Helena...
A 108-day period of no more than three-quarters of an inch
accumulated precipitation occurred between June 30 and October 15.
This is the 20th longest of no more than three-quarters inch and
longest since 2004. The record is 165-days.
Records for Bozeman began in 1935...Cut Bank began in 1903...Dillon
began in 1939...Great Falls began in 1891...Havre and Helena began
in 1880...and Lewistown began in 1896. West Yellowstone records began
in 1905...winds began in 2010. Bozeman MSUs records began in 1868
for precipitation and 1892 for temperature and snowfall. The normal
period for all elements is 1981 to 2010.
These data are preliminary and have not undergone final QC by NCEI.
Therefore these data are subject to revision. Final and certified
climate data can be accessed at the National Centers for
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