Built 2026-10-19 (19 October 2026)

Rocky Boy Weather Records (USS0009A01S)

Record envelope, standing records and threshold days for Rocky Boy (USS0009A01S), Montana, United States, with 31 years of record.

Key Facts for Rocky Boy

  • Rocky Boy (USS0009A01S) is a weather station in Montana, United States at 48.17 latitude and -109.65 longitude, 1,433 m (4,700 ft) above sea level.
  • The station reports from 1996 to 2026, 31 years of record.
  • 1,464 records set at Rocky Boy still stand.
  • Records are tracked for tmax, tmin: an element needs 30 years of data to be eligible.
  • Rocky Boy set a daily record low minimum temperature of -4.2 C (24.4 F) on 27 September 2026 (provisional).

Provisional Records

Records set in the last 60 days are provisional until they clear the revision window.

About the Station

  • Location: Montana, United States, 48.17 latitude, -109.65 longitude.
  • Elevation: 1,433 m (4,700 ft).
  • Period of record: 1996 to 2026, 31 years.
  • Eligible elements: tmax, tmin.

Daily Record Envelope and 2026

23 days at or beyond a record
Daily record high and record low at Rocky Boy, with 2026 drawn through them The band shows the record high and record low for each calendar day at Rocky Boy. The lines show the 2026 daily maximum and minimum. 23 days in 2026 matched or passed a record. Temperatures are in degrees Celsius. -40-2002040 JanFebMarAprMayJunJulAugSepOctNovDec
The band shows the record high and record low for each calendar day at Rocky Boy. The lines show the 2026 daily maximum and minimum. 23 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.
Daily record high and record low at Rocky Boy, with 2026 drawn through them
MonthHighest record highLowest record low2026 highest maximum2026 lowest minimum
Jan17.3 C (63.1 F)-38.6 C (-37.5 F)12.6 C (54.7 F)-32.1 C (-25.8 F)
Feb17.1 C (62.8 F)-36.4 C (-33.5 F)13.9 C (57.0 F)-25.6 C (-14.1 F)
Mar21.2 C (70.2 F)-33.1 C (-27.6 F)19.2 C (66.6 F)-26.6 C (-15.9 F)
Apr25.0 C (77.0 F)-24.1 C (-11.4 F)19.3 C (66.7 F)-12.7 C (9.1 F)
May28.1 C (82.6 F)-13.8 C (7.2 F)27.6 C (81.7 F)-9.7 C (14.5 F)
Jun33.3 C (91.9 F)-4.4 C (24.1 F)23.9 C (75.0 F)-0.9 C (30.4 F)
Jul35.7 C (96.3 F)0.0 C (32.0 F)34.3 C (93.7 F)4.0 C (39.2 F)
Aug36.5 C (97.7 F)-2.2 C (28.0 F)33.7 C (92.7 F)-0.9 C (30.4 F)
Sep33.6 C (92.5 F)-12.3 C (9.9 F)24.7 C (76.5 F)-4.2 C (24.4 F)
Oct28.0 C (82.4 F)-22.9 C (-9.2 F)23.2 C (73.8 F)-5.7 C (21.7 F)
Nov23.0 C (73.4 F)-27.5 C (-17.5 F)n/an/a
Dec16.2 C (61.2 F)-37.4 C (-35.3 F)n/an/a

Which Years Hold Standing Records

1,464 standing records
Standing records at Rocky Boy by the year they were set 1,464 records at Rocky Boy still stand. 2022 holds the most, with 72. 0204060801996: 431997: 511998: 371999: 452000: 342001: 262002: 522003: 562004: 362005: 642006: 502007: 422008: 422009: 522010: 442011: 312012: 552013: 422014: 462015: 442016: 532017: 522018: 312019: 462020: 482021: 712022: 722023: 542024: 602025: 422026: 4319962000200420082012201620202024
1,464 records at Rocky Boy still stand. 2022 holds the most, with 72.
Standing records at Rocky Boy by the year they were set
Year setStanding records
199643
199751
199837
199945
200034
200126
200252
200356
200436
200564
200650
200742
200842
200952
201044
201131
201255
201342
201446
201544
201653
201752
201831
201946
202048
202171
202272
202354
202460
202542
202643

Wettest Day of Each Month

Sep: 137.2 mm (5.4 in)
Record daily precipitation for each month at Rocky Boy The wettest day on record for each calendar month at Rocky Boy. The most was 137.2 mm (5.4 in) on 18 September 2024. 050100150 Jan: 50.8 mm (2.0 in), 11 January 2025 Jan Feb: 25.4 mm (1.0 in), 26 February 1999 Feb Mar: 20.3 mm (0.8 in), 27 March 2007 Mar Apr: 66.0 mm (2.6 in), 29 April 2010 Apr May: 134.6 mm (5.3 in), 7 May 2024 May Jun: 99.1 mm (3.9 in), 27 June 1998 Jun Jul: 61.0 mm (2.4 in), 28 July 2015 Jul Aug: 71.1 mm (2.8 in), 23 August 2014 Aug Sep: 137.2 mm (5.4 in), 18 September 2024 Sep Oct: 61.0 mm (2.4 in), 31 October 2016 Oct Nov: 43.2 mm (1.7 in), 5 November 2024 Nov Dec: 43.2 mm (1.7 in), 10 December 2025 Dec
The wettest day on record for each calendar month at Rocky Boy. The most was 137.2 mm (5.4 in) on 18 September 2024.
Record daily precipitation for each month at Rocky Boy
MonthRecord daily precipitation (mm)Date
Jan50.8 mm (2.0 in)11 January 2025
Feb25.4 mm (1.0 in)26 February 1999
Mar20.3 mm (0.8 in)27 March 2007
Apr66.0 mm (2.6 in)29 April 2010
May134.6 mm (5.3 in)7 May 2024
Jun99.1 mm (3.9 in)27 June 1998
Jul61.0 mm (2.4 in)28 July 2015
Aug71.1 mm (2.8 in)23 August 2014
Sep137.2 mm (5.4 in)18 September 2024
Oct61.0 mm (2.4 in)31 October 2016
Nov43.2 mm (1.7 in)5 November 2024
Dec43.2 mm (1.7 in)10 December 2025

Period of Record Coverage

1996 to 2026
Days with data per year at Rocky Boy 31 years of record at Rocky Boy, 1996 to 2026. 2 years have data for under 90 percent of days and are left out of rankings: 1996, 2026. 1996: 204 of 366 days1997: 365 of 365 days1998: 365 of 365 days1999: 363 of 365 days2000: 366 of 366 days2001: 364 of 365 days2002: 364 of 365 days2003: 365 of 365 days2004: 365 of 366 days2005: 364 of 365 days2006: 365 of 365 days2007: 365 of 365 days2008: 365 of 366 days2009: 365 of 365 days2010: 365 of 365 days2011: 365 of 365 days2012: 366 of 366 days2013: 365 of 365 days2014: 365 of 365 days2015: 365 of 365 days2016: 366 of 366 days2017: 364 of 365 days2018: 365 of 365 days2019: 363 of 365 days2020: 363 of 366 days2021: 364 of 365 days2022: 363 of 365 days2023: 364 of 365 days2024: 366 of 366 days2025: 363 of 365 days2026: 277 of 365 days200020052010201520202025
31 years of record at Rocky Boy, 1996 to 2026. 2 years have data for under 90 percent of days and are left out of rankings: 1996, 2026.
Days with data per year at Rocky Boy
YearDays with dataShare of yearComplete
199620456%No
1997365100%Yes
1998365100%Yes
199936399%Yes
2000366100%Yes
2001364100%Yes
2002364100%Yes
2003365100%Yes
2004365100%Yes
2005364100%Yes
2006365100%Yes
2007365100%Yes
2008365100%Yes
2009365100%Yes
2010365100%Yes
2011365100%Yes
2012366100%Yes
2013365100%Yes
2014365100%Yes
2015365100%Yes
2016366100%Yes
2017364100%Yes
2018365100%Yes
201936399%Yes
202036399%Yes
2021364100%Yes
202236399%Yes
2023364100%Yes
2024366100%Yes
202536399%Yes
202627776%No

Latest Records

20
Latest records at Rocky Boy
DateStationRecordValueBeat old record byOld record stoodSignificance
27 September 2026Rocky Boy, USdaily low min (Provisional)-4.2 C (24.4 F)0.1 C (0.2 F)16 years8 of 100 (Routine)
22 August 2026Rocky Boy, USdaily high min (Tie, Provisional)13.6 C (56.5 F)tie23 years2 of 100 (Routine)
14 August 2026Rocky Boy, USdaily low max14.8 C (58.6 F)0.5 C (0.9 F)16 years8 of 100 (Routine)
5 August 2026Rocky Boy, USdaily low min1.7 C (35.1 F)1.6 C (2.9 F)4 years8 of 100 (Routine)
4 August 2026Rocky Boy, USdaily low min-0.9 C (30.4 F)3.0 C (5.4 F)17 years17 of 100 (Routine)
3 August 2026Rocky Boy, USdaily low min-0.2 C (31.6 F)2.1 C (3.8 F)24 years16 of 100 (Routine)
1 August 2026Rocky Boy, USdaily high max33.7 C (92.7 F)1.3 C (2.3 F)4 years6 of 100 (Routine)
25 July 2026Rocky Boy, USdaily high max34.3 C (93.7 F)2.4 C (4.3 F)1 year8 of 100 (Routine)
14 July 2026Rocky Boy, USdaily high min14.4 C (57.9 F)0.2 C (0.4 F)24 years10 of 100 (Routine)
12 July 2026Rocky Boy, USdaily high max34.1 C (93.4 F)1.5 C (2.7 F)24 years13 of 100 (Routine)
29 June 2026Rocky Boy, USdaily low max11.8 C (53.2 F)0.4 C (0.7 F)20 years9 of 100 (Routine)
14 June 2026Rocky Boy, USdaily low min-0.9 C (30.4 F)1.3 C (2.3 F)17 years11 of 100 (Routine)
2 June 2026Rocky Boy, USdaily low max7.6 C (45.7 F)0.2 C (0.4 F)28 years11 of 100 (Routine)
1 June 2026Rocky Boy, USdaily low max5.7 C (42.3 F)1.2 C (2.2 F)25 years12 of 100 (Routine)
29 May 2026Rocky Boy, USdaily high max26.1 C (79.0 F)2.3 C (4.1 F)0 years6 of 100 (Routine)
28 May 2026Rocky Boy, USdaily high max27.6 C (81.7 F)2.8 C (5.0 F)8 years9 of 100 (Routine)
27 May 2026Rocky Boy, USdaily high max26.4 C (79.5 F)2.9 C (5.2 F)27 years15 of 100 (Routine)
27 May 2026Rocky Boy, USdaily high min11.5 C (52.7 F)1.6 C (2.9 F)16 years12 of 100 (Routine)
26 May 2026Rocky Boy, USdaily high max27.0 C (80.6 F)2.6 C (4.7 F)8 years9 of 100 (Routine)
17 May 2026Rocky Boy, USdaily low max1.1 C (34.0 F)3.4 C (6.1 F)11 years11 of 100 (Routine)

Climate Trend

29 complete years, 1997 to 2025
Annual mean temperature at Rocky Boy as warming stripes, 1997 to 2025 One stripe for each of 29 complete years at Rocky Boy, 1997 to 2025. Blue stripes are years cooler than the station's own mean of 4.2 C (39.5 F); red stripes are warmer. The coolest year was 2019, at 2.7 C (36.9 F), and the warmest was 2015, at 5.5 C (41.8 F). The strongest colour marks a difference of 1.5 C (2.7 F). 1997: 3.7 C, -0.5 C from the station mean1998: 4.5 C, +0.3 C from the station mean1999: 4.6 C, +0.4 C from the station mean2000: 3.3 C, -0.9 C from the station mean2001: 4.4 C, +0.2 C from the station mean2002: 2.9 C, -1.3 C from the station mean2003: 4.3 C, +0.1 C from the station mean2004: 3.9 C, -0.3 C from the station mean2005: 4.3 C, +0.1 C from the station mean2006: 5.1 C, +0.9 C from the station mean2007: 4.7 C, +0.5 C from the station mean2008: 3.4 C, -0.8 C from the station mean2009: 3.4 C, -0.8 C from the station mean2010: 3.9 C, -0.3 C from the station mean2011: 3.7 C, -0.5 C from the station mean2012: 5.1 C, +0.9 C from the station mean2013: 4.1 C, -0.1 C from the station mean2014: 3.7 C, -0.5 C from the station mean2015: 5.5 C, +1.3 C from the station mean2016: 5.3 C, +1.1 C from the station mean2017: 4.6 C, +0.4 C from the station mean2018: 3.8 C, -0.4 C from the station mean2019: 2.7 C, -1.4 C from the station mean2020: 4.3 C, +0.1 C from the station mean2021: 4.3 C, +0.1 C from the station mean2022: 3.7 C, -0.5 C from the station mean2023: 4.8 C, +0.6 C from the station mean2024: 5.0 C, +0.8 C from the station mean2025: 4.6 C, +0.4 C from the station mean1997200020052010201520202025
One stripe for each of 29 complete years at Rocky Boy, 1997 to 2025. Blue stripes are years cooler than the station's own mean of 4.2 C (39.5 F); red stripes are warmer. The coolest year was 2019, at 2.7 C (36.9 F), and the warmest was 2015, at 5.5 C (41.8 F). The strongest colour marks a difference of 1.5 C (2.7 F).
Annual mean temperature at Rocky Boy as warming stripes, 1997 to 2025
YearAnnual mean temperatureDifference from the station mean
19973.7 C-0.49 C
19984.5 C+0.34 C
19994.6 C+0.42 C
20003.3 C-0.87 C
20014.4 C+0.20 C
20022.9 C-1.33 C
20034.3 C+0.08 C
20043.9 C-0.26 C
20054.3 C+0.08 C
20065.1 C+0.94 C
20074.7 C+0.49 C
20083.4 C-0.82 C
20093.4 C-0.83 C
20103.9 C-0.32 C
20113.7 C-0.47 C
20125.1 C+0.86 C
20134.1 C-0.14 C
20143.7 C-0.47 C
20155.5 C+1.28 C
20165.3 C+1.07 C
20174.6 C+0.39 C
20183.8 C-0.44 C
20192.7 C-1.45 C
20204.3 C+0.12 C
20214.3 C+0.11 C
20223.7 C-0.48 C
20234.8 C+0.64 C
20245.0 C+0.79 C
20254.6 C+0.43 C

This station does not have enough complete years (30 are needed) to fit a temperature trend.

A year is complete when all 12 months have at least 20 days of both daily maximum and daily minimum readings. The annual mean is the mean of the monthly means. The trend describes this one station over this period; it does not say what caused the change.

Extremes by Year

1996 to 2026
Yearly extremes at Rocky Boy: the record and the median year
MeasureRecordYear of the recordMedian yearYears with a value
Hottest day (TXx)36.5 C (97.7 F)201832.9 C (91.2 F)31
Coldest night (TNn)-38.6 C (-37.5 F)2024-32.9 C (-27.2 F)31
Wettest day (Rx1day)137.2 mm (5.4 in)202440.6 mm (1.6 in)31
Wettest five days (Rx5day)233.6 mm (9.2 in)201396.4 mm (3.8 in)31
Longest dry spell (CDD)80 days201727 days31

Hottest day (TXx)

Hottest day (TXx) at Rocky Boy by year The hottest day of the year at Rocky Boy, 1996 to 2026. The record is 36.5 C (97.7 F) in 2018, marked on the chart; the median year is 32.9 C (91.2 F). 283032343638200020052010201520202025Record: 36.5 C (97.7 F) in 2018
The hottest day of the year at Rocky Boy, 1996 to 2026. The record is 36.5 C (97.7 F) in 2018, marked on the chart; the median year is 32.9 C (91.2 F).
Hottest day (TXx) at Rocky Boy by year
YearHottest day (TXx)
199632.8 C (91.0 F)
199729.8 C (85.6 F)
199831.5 C (88.7 F)
199931.3 C (88.3 F)
200031.2 C (88.2 F)
200134.3 C (93.7 F)
200232.9 C (91.2 F)
200333.0 C (91.4 F)
200431.8 C (89.2 F)
200531.5 C (88.7 F)
200633.0 C (91.4 F)
200734.6 C (94.3 F)
200832.2 C (90.0 F)
200930.8 C (87.4 F)
201032.0 C (89.6 F)
201133.6 C (92.5 F)
201232.9 C (91.2 F)
201333.7 C (92.7 F)
201431.6 C (88.9 F)
201533.0 C (91.4 F)
201633.0 C (91.4 F)
201733.7 C (92.7 F)
201836.5 C (97.7 F)
201932.4 C (90.3 F)
202033.0 C (91.4 F)
202134.4 C (93.9 F)
202234.4 C (93.9 F)
202332.6 C (90.7 F)
202435.7 C (96.3 F)
202530.4 C (86.7 F)
202634.3 C (93.7 F)

Coldest night (TNn)

Coldest night (TNn) at Rocky Boy by year The coldest night of the year at Rocky Boy, 1996 to 2026. The record is -38.6 C (-37.5 F) in 2024, marked on the chart; the median year is -32.9 C (-27.2 F). -40-35-30-25200020052010201520202025Record: -38.6 C (-37.5 F) in 2024
The coldest night of the year at Rocky Boy, 1996 to 2026. The record is -38.6 C (-37.5 F) in 2024, marked on the chart; the median year is -32.9 C (-27.2 F).
Coldest night (TNn) at Rocky Boy by year
YearColdest night (TNn)
1996-30.7 C (-23.3 F)
1997-35.3 C (-31.5 F)
1998-33.6 C (-28.5 F)
1999-25.7 C (-14.3 F)
2000-32.0 C (-25.6 F)
2001-26.2 C (-15.2 F)
2002-29.3 C (-20.7 F)
2003-31.8 C (-25.2 F)
2004-33.3 C (-27.9 F)
2005-33.9 C (-29.0 F)
2006-32.8 C (-27.0 F)
2007-30.3 C (-22.5 F)
2008-37.1 C (-34.8 F)
2009-33.1 C (-27.6 F)
2010-28.4 C (-19.1 F)
2011-34.2 C (-29.6 F)
2012-31.0 C (-23.8 F)
2013-37.4 C (-35.3 F)
2014-34.7 C (-30.5 F)
2015-26.4 C (-15.5 F)
2016-34.1 C (-29.4 F)
2017-32.9 C (-27.2 F)
2018-31.8 C (-25.2 F)
2019-35.0 C (-31.0 F)
2020-31.5 C (-24.7 F)
2021-36.4 C (-33.5 F)
2022-35.5 C (-31.9 F)
2023-31.2 C (-24.2 F)
2024-38.6 C (-37.5 F)
2025-33.1 C (-27.6 F)
2026-32.1 C (-25.8 F)

Wettest day (Rx1day)

Wettest day (Rx1day) at Rocky Boy by year The wettest day of the year at Rocky Boy, 1996 to 2026. The record is 137.2 mm (5.4 in) in 2024, marked on the chart; the median year is 40.6 mm (1.6 in). 050100150200020052010201520202025Record: 137.2 mm (5.4 in) in 2024
The wettest day of the year at Rocky Boy, 1996 to 2026. The record is 137.2 mm (5.4 in) in 2024, marked on the chart; the median year is 40.6 mm (1.6 in).
Wettest day (Rx1day) at Rocky Boy by year
YearWettest day (Rx1day)
199617.8 mm (0.7 in)
199730.5 mm (1.2 in)
199899.1 mm (3.9 in)
199930.5 mm (1.2 in)
200033.0 mm (1.3 in)
200138.1 mm (1.5 in)
200238.1 mm (1.5 in)
200330.5 mm (1.2 in)
200433.0 mm (1.3 in)
200543.2 mm (1.7 in)
200635.6 mm (1.4 in)
200735.6 mm (1.4 in)
200840.6 mm (1.6 in)
200930.5 mm (1.2 in)
201076.2 mm (3.0 in)
201171.1 mm (2.8 in)
201266.0 mm (2.6 in)
201378.7 mm (3.1 in)
201471.1 mm (2.8 in)
201561.0 mm (2.4 in)
201661.0 mm (2.4 in)
201758.4 mm (2.3 in)
201827.9 mm (1.1 in)
201953.3 mm (2.1 in)
202038.1 mm (1.5 in)
202138.1 mm (1.5 in)
202299.1 mm (3.9 in)
202333.0 mm (1.3 in)
2024137.2 mm (5.4 in)
202550.8 mm (2.0 in)
202668.6 mm (2.7 in)

Wettest five days (Rx5day)

Wettest five days (Rx5day) at Rocky Boy by year The wettest five days of the year at Rocky Boy, 1996 to 2026. The record is 233.6 mm (9.2 in) in 2013, marked on the chart; the median year is 96.4 mm (3.8 in). 0100200300200020052010201520202025Record: 233.6 mm (9.2 in) in 2013
The wettest five days of the year at Rocky Boy, 1996 to 2026. The record is 233.6 mm (9.2 in) in 2013, marked on the chart; the median year is 96.4 mm (3.8 in).
Wettest five days (Rx5day) at Rocky Boy by year
YearWettest five days (Rx5day)
199622.8 mm (0.9 in)
199758.4 mm (2.3 in)
1998170.2 mm (6.7 in)
199955.9 mm (2.2 in)
200060.9 mm (2.4 in)
200143.2 mm (1.7 in)
2002101.6 mm (4.0 in)
200371.1 mm (2.8 in)
200461.0 mm (2.4 in)
200589.0 mm (3.5 in)
200696.6 mm (3.8 in)
200771.2 mm (2.8 in)
200899.0 mm (3.9 in)
200948.2 mm (1.9 in)
2010114.2 mm (4.5 in)
2011106.7 mm (4.2 in)
201296.4 mm (3.8 in)
2013233.6 mm (9.2 in)
2014121.8 mm (4.8 in)
2015121.9 mm (4.8 in)
2016106.7 mm (4.2 in)
2017104.0 mm (4.1 in)
201863.5 mm (2.5 in)
2019124.4 mm (4.9 in)
202063.5 mm (2.5 in)
202183.8 mm (3.3 in)
2022165.1 mm (6.5 in)
202358.4 mm (2.3 in)
2024215.8 mm (8.5 in)
202586.3 mm (3.4 in)
2026137.2 mm (5.4 in)

Longest dry spell (CDD)

Longest dry spell (CDD) at Rocky Boy by year The longest dry spell of the year at Rocky Boy, 1996 to 2026. The record is 80 days in 2017, marked on the chart; the median year is 27 days. 020406080200020052010201520202025Record: 80 days in 2017
The longest dry spell of the year at Rocky Boy, 1996 to 2026. The record is 80 days in 2017, marked on the chart; the median year is 27 days.
Longest dry spell (CDD) at Rocky Boy by year
YearLongest dry spell (CDD)
199611 days
199717 days
199827 days
199917 days
200022 days
200131 days
200220 days
200328 days
200431 days
200553 days
200644 days
200725 days
200821 days
200939 days
201025 days
201165 days
201243 days
201327 days
201450 days
201525 days
201619 days
201780 days
201852 days
201945 days
202024 days
202126 days
202231 days
202332 days
202428 days
202516 days
202618 days

Each chart shows one value per year; the dot marks the record year. TXx is the hottest daily maximum, TNn the coldest daily minimum, Rx1day and Rx5day the largest one-day and five-day rain totals, and CDD the longest run of days with less than 1 mm of rain. A year with missing days can understate an extreme.

Frost Dates and Growing Season

29 years with a frost

Across 29 years with a frost, the median last spring frost at Rocky Boy falls on 15 June and the median first autumn frost on 4 September, which leaves a median of 84 days between them.

Fitted over all years, the growing season changes by +1.9 days per decade at this station.

Frost dates and growing season at Rocky Boy
MeasureMedian, all yearsEarliest periodRecent period (1997 to 2025)Recent against earliestFitted trend
Last spring frost15 Junen/a15 Junen/a+3.0 days per decade
First autumn frost4 Septembern/a4 Septembern/a+4.9 days per decade
Growing days84 daysn/a84 daysn/a+1.9 days per decade

A frost day is a day with a daily minimum at or below 0 C (32 F). The last spring frost and the first autumn frost are the last and first such days of the cold season, and growing days are the days between them. A negative trend for the last spring frost means it comes earlier.

Download the Data

  • Data for Rocky Boy standing records by year: CSV or JSON. Field meanings are on the data page.
  • Data for Rocky Boy threshold days by year: CSV or JSON. Field meanings are on the data page.

Source: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily). Records are computed by World Extreme Weather Monitor and are not official NOAA products. (US Government open data (NOAA NCEI)) Data as of 2026-10-17 (17 October 2026). Records are computed by this site and are not official.

Data as of . Last revised (2026-10-17).