Potomac Threshold Days by Year (USC00246685)

14 fixed thresholds counted per year at Potomac (USC00246685): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Potomac Thresholds

Potomac: days with a maximum temperature at or above 30 C (86 F) in 47 years, most in 2007 with 53.
Potomac: days with a maximum temperature at or below 0 C (32 F) in 47 years, most in 1985 with 75.
Potomac: days with a maximum temperature at or above 90 F (32.2 C) in 46 years, most in 2007 with 33.
Potomac: days with 10 mm (0.39 in) or more of precipitation in 45 years, most in 1995 with 16.
14 fixed thresholds have at least one qualifying day at Potomac.

Days at or above 30 C (86 F)

47 years with a qualifying day

Days per year at Potomac with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 53 in 2007.

Days at or above 30 C (86 F) per year at Potomac
Year	Days	Decade average
1965	22	33
1966	33	33
1967	47	33
1968	26	33
1969	37	33
1970	40	34.3
1971	40	34.3
1976	29	34.3
1977	35	34.3
1978	25	34.3
1979	37	34.3
1980	8	32.4
1981	42	32.4
1982	23	32.4
1983	32	32.4
1984	41	32.4
1985	35	32.4
1986	36	32.4
1987	32	32.4
1988	46	32.4
1989	29	32.4
1990	39	27
1991	32	27
1992	27	27
1993	11	27
1995	19	27
1996	34	27
1997	19	27
1998	37	27
1999	25	27
2000	37	34.9
2001	36	34.9
2002	20	34.9
2004	29	34.9
2005	34	34.9
2006	51	34.9
2007	53	34.9
2008	19	34.9
2018	28	28
2019	28	28
2020	29	34
2021	48	34
2022	46	34
2023	25	34
2024	36	34
2025	52	34
2026	2	34

For each year, a bar from the first to the last day at Potomac meeting 30 C (86 F).

First to last qualifying date each year at Potomac
Year	First date	Last date
1965	1965-06-10	1965-08-19
1966	1966-05-03	1966-09-22
1967	1967-07-02	1967-09-29
1968	1968-06-26	1968-09-10
1969	1969-05-23	1969-09-11
1970	1970-06-03	1970-08-30
1971	1971-06-22	1971-09-10
1976	1976-06-28	1976-09-16
1977	1977-06-01	1977-08-21
1978	1978-06-28	1978-09-26
1979	1979-05-23	1979-09-15
1980	1980-05-21	1980-09-05
1981	1981-06-25	1981-09-19
1982	1982-07-20	1982-09-04
1983	1983-05-28	1983-09-01
1984	1984-05-29	1984-09-18
1985	1985-05-23	1985-07-29
1986	1986-05-25	1986-08-28
1987	1987-04-28	1987-09-24
1988	1988-05-22	1988-09-06
1989	1989-06-08	1989-09-23
1990	1990-06-22	1990-09-15
1991	1991-07-03	1991-09-06
1992	1992-06-10	1992-10-02
1993	1993-05-11	1993-08-11
1995	1995-06-26	1995-09-03
1996	1996-06-07	1996-08-30
1997	1997-07-05	1997-09-01
1998	1998-07-10	1998-09-17
1999	1999-05-25	1999-08-31
2000	2000-06-07	2000-09-17
2001	2001-05-12	2001-09-24
2002	2002-06-17	2002-09-15
2004	2004-06-24	2004-09-01
2005	2005-06-20	2005-09-08
2006	2006-05-16	2006-09-08
2007	2007-06-03	2007-09-04
2008	2008-06-21	2008-08-24
2018	2018-07-06	2018-09-08
2019	2019-06-13	2019-09-16
2020	2020-05-31	2020-09-13
2021	2021-06-03	2021-09-09
2022	2022-06-18	2022-09-08
2023	2023-05-22	2023-09-18
2024	2024-06-27	2024-09-29
2025	2025-05-30	2025-09-29
2026	2026-05-26	2026-05-29

Every Fixed Threshold

Fixed thresholds at Potomac
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
30 C (86 F): Days	47	53	2007	2
35 C (95 F): Days	38	14	2007	5
90 F (32.2 C): Days	46	33	2007	28
100 F (37.8 C): Days	10	3	2002	2
0 C (32 F): Ice days (max	47	75	1985	10
0 C (32 F): Frost days (min	37	261	2021	131
-10 C (14 F): Days with min	37	106	2019	26
-20 C (-4 F): Days with min	36	35	2019	20
-30 C (-22 F): Days with min	28	12	1979	6
-40 C (-40 F): Days with min	9	4	1983	2
10 mm (0.39 in): Days with 10 mm or more rain	45	16	1995	7
25 mm (0.98 in): Days with 25 mm or more rain	22	3	1980	2
10 cm (3.9 in): Days with 10 cm or more snowfall	44	17	1996	2
25 cm (9.8 in): Days with 25 cm or more snowfall	7	2	1996	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1965.

Download the Data

Data for Potomac 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). Threshold counts are computed by this site.

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

Potomac Threshold Days by Year (USC00246685)

Key Facts for Potomac Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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