Rocky Boy Weather Records (USC00247148)

Record envelope, standing records and threshold days for Rocky Boy (USC00247148), Montana, United States, with 37 years of record.

Key Facts for Rocky Boy

Rocky Boy (USC00247148) is a weather station in Montana, United States at 48.25 latitude and -109.78 longitude, 1,125 m (3,691 ft) above sea level.
The station reports from 1951 to 1987, 37 years of record.
16 records set at Rocky Boy still stand.
Records are tracked for prcp: an element needs 30 years of data to be eligible.
Rocky Boy set a daily record precipitation of 20.3 mm (0.8 in) on 27 May 1987.

About the Station

Location: Montana, United States, 48.25 latitude, -109.78 longitude.
Elevation: 1,125 m (3,691 ft).
Period of record: 1951 to 1987, 37 years.
Eligible elements: prcp.

Daily Record Envelope and 2026

0 days at or beyond a record

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. 0 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
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	n/a	n/a	n/a	n/a
Feb	n/a	n/a	n/a	n/a
Mar	n/a	n/a	n/a	n/a
Apr	n/a	n/a	n/a	n/a
May	n/a	n/a	n/a	n/a
Jun	n/a	n/a	n/a	n/a
Jul	n/a	n/a	n/a	n/a
Aug	n/a	n/a	n/a	n/a
Sep	n/a	n/a	n/a	n/a
Oct	n/a	n/a	n/a	n/a
Nov	3.9 C (39.0 F)	-22.2 C (-8.0 F)	n/a	n/a
Dec	n/a	n/a	n/a	n/a

Which Years Hold Standing Records

16 standing records

16 records at Rocky Boy still stand. 1979 holds the most, with 16.

Wettest Day of Each Month

Jun: 111.8 mm (4.4 in)

The wettest day on record for each calendar month at Rocky Boy. The most was 111.8 mm (4.4 in) on 26 June 1965.

Record daily precipitation for each month at Rocky Boy
Month	Record daily precipitation (mm)	Date
Jan	21.6 mm (0.9 in)	21 January 1965
Feb	11.4 mm (0.4 in)	20 February 1963
Mar	19.1 mm (0.8 in)	6 March 1953
Apr	27.2 mm (1.1 in)	24 April 1973
May	101.6 mm (4.0 in)	30 May 1982
Jun	111.8 mm (4.4 in)	26 June 1965
Jul	75.7 mm (3.0 in)	10 July 1983
Aug	77.7 mm (3.1 in)	19 August 1964
Sep	74.4 mm (2.9 in)	13 September 1967
Oct	52.8 mm (2.1 in)	20 October 1958
Nov	15.0 mm (0.6 in)	2 November 1983
Dec	18.5 mm (0.7 in)	16 December 1977

Period of Record Coverage

1979 to 1979

1 years of record at Rocky Boy, 1979 to 1979. 1 years have data for under 90 percent of days and are left out of rankings: 1979.

Latest Records

Latest records at Rocky Boy
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
27 May 1987	Rocky Boy, US	daily rain	20.3 mm (0.8 in)	1.2 mm (0.05 in)	16 years	8 of 100 (Routine)
27 March 1987	Rocky Boy, US	daily rain	15.0 mm (0.6 in)	6.9 mm (0.27 in)	12 years	20 of 100 (Routine)
20 March 1987	Rocky Boy, US	daily rain	2.8 mm (0.11 in)	0.3 mm (0.01 in)	34 years	13 of 100 (Routine)
14 January 1987	Rocky Boy, US	daily rain	4.3 mm (0.17 in)	1.5 mm (0.06 in)	28 years	15 of 100 (Routine)
12 November 1986	Rocky Boy, US	daily rain	6.1 mm (0.24 in)	2.8 mm (0.11 in)	29 years	20 of 100 (Routine)
31 October 1986	Rocky Boy, US	daily rain	10.2 mm (0.4 in)	8.2 mm (0.32 in)	16 years	19 of 100 (Routine)
25 September 1986	Rocky Boy, US	daily rain	50.8 mm (2.0 in)	32.8 mm (1.3 in)	4 years	43 of 100 (Notable)
19 September 1986	Rocky Boy, US	daily rain	22.6 mm (0.9 in)	16.2 mm (0.6 in)	33 years	20 of 100 (Routine)
18 September 1986	Rocky Boy, US	daily rain	33.0 mm (1.3 in)	20.3 mm (0.8 in)	0 years	27 of 100 (Routine)
17 September 1986	Rocky Boy, US	daily rain	25.1 mm (1.0 in)	13.9 mm (0.5 in)	11 years	22 of 100 (Routine)
10 September 1986	Rocky Boy, US	daily rain	4.8 mm (0.19 in)	0.7 mm (0.03 in)	12 years	6 of 100 (Routine)
5 September 1986	Rocky Boy, US	daily rain	19.1 mm (0.8 in)	11.2 mm (0.4 in)	8 years	18 of 100 (Routine)
31 August 1986	Rocky Boy, US	daily rain	17.8 mm (0.7 in)	5.1 mm (0.20 in)	1 year	7 of 100 (Routine)
14 August 1986	Rocky Boy, US	daily rain	17.8 mm (0.7 in)	3.8 mm (0.15 in)	12 years	9 of 100 (Routine)
24 July 1986	Rocky Boy, US	daily rain	1.5 mm (0.06 in)	0.2 mm (0.01 in)	4 years	4 of 100 (Routine)
17 July 1986	Rocky Boy, US	daily rain	17.8 mm (0.7 in)	10.4 mm (0.4 in)	8 years	16 of 100 (Routine)
23 May 1986	Rocky Boy, US	daily rain	38.9 mm (1.5 in)	29.5 mm (1.2 in)	20 years	33 of 100 (Routine)
22 May 1986	Rocky Boy, US	daily rain	49.5 mm (1.9 in)	44.4 mm (1.7 in)	31 years	48 of 100 (Notable)
12 May 1986	Rocky Boy, US	daily rain	50.8 mm (2.0 in)	39.1 mm (1.5 in)	0 years	35 of 100 (Notable)
9 May 1986	Rocky Boy, US	daily rain	17.8 mm (0.7 in)	8.9 mm (0.35 in)	8 years	12 of 100 (Routine)

Extremes by Year

1951 to 1987

Yearly extremes at Rocky Boy: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	3.9 C (39.0 F)	1979	3.9 C (39.0 F)	1
Coldest night (TNn)	-22.2 C (-8.0 F)	1979	-22.2 C (-8.0 F)	1
Wettest day (Rx1day)	111.8 mm (4.4 in)	1965	41.4 mm (1.6 in)	37
Wettest five days (Rx5day)	193.4 mm (7.6 in)	1965	59.7 mm (2.4 in)	37
Longest dry spell (CDD)	67 days	1969	31 days	37

Hottest day (TXx)

The hottest day of the year at Rocky Boy, 1951 to 1987. The record is 3.9 C (39.0 F) in 1979, marked on the chart; the median year is 3.9 C (39.0 F).

Hottest day (TXx) at Rocky Boy by year
Year	Hottest day (TXx)
1951	n/a
1952	n/a
1953	n/a
1954	n/a
1955	n/a
1956	n/a
1957	n/a
1958	n/a
1959	n/a
1960	n/a
1961	n/a
1962	n/a
1963	n/a
1964	n/a
1965	n/a
1966	n/a
1967	n/a
1968	n/a
1969	n/a
1970	n/a
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	n/a
1978	n/a
1979	3.9 C (39.0 F)
1980	n/a
1981	n/a
1982	n/a
1983	n/a
1984	n/a
1985	n/a
1986	n/a
1987	n/a

Coldest night (TNn)

The coldest night of the year at Rocky Boy, 1951 to 1987. The record is -22.2 C (-8.0 F) in 1979, marked on the chart; the median year is -22.2 C (-8.0 F).

Coldest night (TNn) at Rocky Boy by year
Year	Coldest night (TNn)
1951	n/a
1952	n/a
1953	n/a
1954	n/a
1955	n/a
1956	n/a
1957	n/a
1958	n/a
1959	n/a
1960	n/a
1961	n/a
1962	n/a
1963	n/a
1964	n/a
1965	n/a
1966	n/a
1967	n/a
1968	n/a
1969	n/a
1970	n/a
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	n/a
1978	n/a
1979	-22.2 C (-8.0 F)
1980	n/a
1981	n/a
1982	n/a
1983	n/a
1984	n/a
1985	n/a
1986	n/a
1987	n/a

Wettest day (Rx1day)

The wettest day of the year at Rocky Boy, 1951 to 1987. The record is 111.8 mm (4.4 in) in 1965, marked on the chart; the median year is 41.4 mm (1.6 in).

Wettest day (Rx1day) at Rocky Boy by year
Year	Wettest day (Rx1day)
1951	41.4 mm (1.6 in)
1952	28.4 mm (1.1 in)
1953	59.4 mm (2.3 in)
1954	36.8 mm (1.4 in)
1955	38.4 mm (1.5 in)
1956	35.1 mm (1.4 in)
1957	30.2 mm (1.2 in)
1958	52.8 mm (2.1 in)
1959	102.9 mm (4.1 in)
1960	30.5 mm (1.2 in)
1961	58.4 mm (2.3 in)
1962	33.5 mm (1.3 in)
1963	23.6 mm (0.9 in)
1964	77.7 mm (3.1 in)
1965	111.8 mm (4.4 in)
1966	37.6 mm (1.5 in)
1967	74.4 mm (2.9 in)
1968	17.0 mm (0.7 in)
1969	43.7 mm (1.7 in)
1970	27.9 mm (1.1 in)
1971	29.7 mm (1.2 in)
1972	20.3 mm (0.8 in)
1973	51.8 mm (2.0 in)
1974	49.5 mm (1.9 in)
1975	47.0 mm (1.9 in)
1976	15.7 mm (0.6 in)
1977	46.0 mm (1.8 in)
1978	43.9 mm (1.7 in)
1979	20.8 mm (0.8 in)
1980	48.8 mm (1.9 in)
1981	66.0 mm (2.6 in)
1982	101.6 mm (4.0 in)
1983	75.7 mm (3.0 in)
1984	21.6 mm (0.9 in)
1985	27.2 mm (1.1 in)
1986	50.8 mm (2.0 in)
1987	20.3 mm (0.8 in)

Wettest five days (Rx5day)

The wettest five days of the year at Rocky Boy, 1951 to 1987. The record is 193.4 mm (7.6 in) in 1965, marked on the chart; the median year is 59.7 mm (2.4 in).

Wettest five days (Rx5day) at Rocky Boy by year
Year	Wettest five days (Rx5day)
1951	69.5 mm (2.7 in)
1952	42.9 mm (1.7 in)
1953	112.2 mm (4.4 in)
1954	64.7 mm (2.5 in)
1955	80.0 mm (3.1 in)
1956	59.7 mm (2.4 in)
1957	35.3 mm (1.4 in)
1958	52.8 mm (2.1 in)
1959	131.7 mm (5.2 in)
1960	37.1 mm (1.5 in)
1961	58.4 mm (2.3 in)
1962	40.8 mm (1.6 in)
1963	32.3 mm (1.3 in)
1964	158.8 mm (6.3 in)
1965	193.4 mm (7.6 in)
1966	51.8 mm (2.0 in)
1967	133.3 mm (5.2 in)
1968	33.0 mm (1.3 in)
1969	89.8 mm (3.5 in)
1970	87.0 mm (3.4 in)
1971	57.8 mm (2.3 in)
1972	22.9 mm (0.9 in)
1973	99.0 mm (3.9 in)
1974	64.0 mm (2.5 in)
1975	52.6 mm (2.1 in)
1976	33.1 mm (1.3 in)
1977	75.7 mm (3.0 in)
1978	63.0 mm (2.5 in)
1979	26.9 mm (1.1 in)
1980	68.6 mm (2.7 in)
1981	88.9 mm (3.5 in)
1982	35.1 mm (1.4 in)
1983	91.0 mm (3.6 in)
1984	26.7 mm (1.1 in)
1985	51.3 mm (2.0 in)
1986	88.4 mm (3.5 in)
1987	23.3 mm (0.9 in)

Longest dry spell (CDD)

The longest dry spell of the year at Rocky Boy, 1951 to 1987. The record is 67 days in 1969, marked on the chart; the median year is 31 days.

Longest dry spell (CDD) at Rocky Boy by year
Year	Longest dry spell (CDD)
1951	27 days
1952	35 days
1953	31 days
1954	28 days
1955	36 days
1956	27 days
1957	33 days
1958	21 days
1959	37 days
1960	40 days
1961	37 days
1962	20 days
1963	38 days
1964	26 days
1965	16 days
1966	38 days
1967	35 days
1968	29 days
1969	67 days
1970	38 days
1971	46 days
1972	26 days
1973	44 days
1974	23 days
1975	27 days
1976	32 days
1977	21 days
1978	18 days
1979	20 days
1980	38 days
1981	37 days
1982	29 days
1983	17 days
1984	36 days
1985	21 days
1986	29 days
1987	32 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.

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 2026-10-13 (13 October 2026). Records are computed by this site and are not official.

Data as of 2025-12-31. Last revised 31 December 2025 (2025-12-31).