Harwell Threshold Days by Year

4 fixed thresholds counted per year at Harwell (ASN00098003): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Harwell Thresholds

Harwell: days with 10 mm (0.39 in) or more of precipitation in 78 years, most in 1992 with 47.
Harwell: days with 25 mm (0.98 in) or more of precipitation in 73 years, most in 1952 with 13.
Harwell: days with 50 mm (1.97 in) or more of precipitation in 21 years, most in 1952 with 4.
Harwell: days with 100 mm (3.94 in) or more of precipitation in 2 years, most in 1946 with 1.
4 fixed thresholds have at least one qualifying day at Harwell.

Days with 10 mm (0.39 in) or more of precipitation

78 years with a qualifying day

Days per year at Harwell with 10 mm (0.39 in) or more of precipitation, with the decade average as a line. The most was 47 in 1992.

Days with 10 mm (0.39 in) or more of precipitation per year at Harwell
Year	Days	Decade average
1941	13	26.1
1942	40	26.1
1943	20	26.1
1944	20	26.1
1945	22	26.1
1946	34	26.1
1947	42	26.1
1948	21	26.1
1949	23	26.1
1950	22	30.7
1951	34	30.7
1952	46	30.7
1953	29	30.7
1954	23	30.7
1955	31	30.7
1956	44	30.7
1957	31	30.7
1958	28	30.7
1959	19	30.7
1960	44	30.4
1961	24	30.4
1962	35	30.4
1963	24	30.4
1964	42	30.4
1965	28	30.4
1966	30	30.4
1967	22	30.4
1968	27	30.4
1969	28	30.4
1970	34	33.1
1971	43	33.1
1972	25	33.1
1973	35	33.1
1974	29	33.1
1975	39	33.1
1976	26	33.1
1977	28	33.1
1978	29	33.1
1979	43	33.1
1980	34	28.7
1981	26	28.7
1982	20	28.7
1983	30	28.7
1984	29	28.7
1985	31	28.7
1986	27	28.7
1987	26	28.7
1988	32	28.7
1989	32	28.7
1990	31	28.8
1991	34	28.8
1992	47	28.8
1993	23	28.8
1994	21	28.8
1995	22	28.8
1996	34	28.8
1997	21	28.8
1998	27	28.8
1999	28	28.8
2000	33	24.1
2001	25	24.1
2002	28	24.1
2003	24	24.1
2004	12	24.1
2005	25	24.1
2006	16	24.1
2007	23	24.1
2008	22	24.1
2009	33	24.1
2010	33	28.4
2011	30	28.4
2012	27	28.4
2013	40	28.4
2014	21	28.4
2015	15	28.4
2016	36	28.4
2017	21	28.4
2018	33	28.4

For each year, a bar from the first to the last day at Harwell meeting 10 mm (0.39 in).

First to last qualifying date each year at Harwell
Year	First date	Last date
1941	1941-01-24	1941-11-20
1942	1942-01-08	1942-12-19
1943	1943-02-18	1943-12-04
1944	1944-02-07	1944-12-21
1945	1945-02-14	1945-12-18
1946	1946-01-04	1946-12-08
1947	1947-01-08	1947-12-25
1948	1948-02-04	1948-12-05
1949	1949-02-21	1949-11-29
1950	1950-02-17	1950-12-08
1951	1951-01-04	1951-12-18
1952	1952-01-11	1952-12-10
1953	1953-04-22	1953-12-07
1954	1954-01-28	1954-12-12
1955	1955-04-01	1955-12-31
1956	1956-01-01	1956-12-13
1957	1957-02-07	1957-12-26
1958	1958-01-31	1958-12-10
1959	1959-01-25	1959-12-25
1960	1960-01-09	1960-12-04
1961	1961-04-07	1961-12-18
1962	1962-01-31	1962-11-11
1963	1963-01-14	1963-10-30
1964	1964-02-07	1964-12-24
1965	1965-03-12	1965-12-13
1966	1966-02-14	1966-12-19
1967	1967-01-13	1967-12-12
1968	1968-03-25	1968-11-19
1969	1969-01-15	1969-11-19
1970	1970-01-03	1970-12-31
1971	1971-01-01	1971-12-31
1972	1972-01-12	1972-11-13
1973	1973-02-06	1973-12-22
1974	1974-02-02	1974-12-28
1975	1975-03-15	1975-11-20
1976	1976-02-09	1976-12-12
1977	1977-01-14	1977-11-29
1978	1978-01-30	1978-12-12
1979	1979-01-17	1979-11-15
1980	1980-01-12	1980-12-03
1981	1981-01-09	1981-11-10
1982	1982-03-23	1982-12-08
1983	1983-03-01	1983-12-06
1984	1984-02-07	1984-12-15
1985	1985-01-31	1985-12-16
1986	1986-02-19	1986-12-17
1987	1987-01-05	1987-12-10
1988	1988-01-01	1988-11-22
1989	1989-01-04	1989-12-27
1990	1990-02-01	1990-12-23
1991	1991-01-24	1991-12-17
1992	1992-01-01	1992-12-28
1993	1993-02-15	1993-12-27
1994	1994-01-08	1994-12-21
1995	1995-01-21	1995-12-04
1996	1996-01-01	1996-12-07
1997	1997-01-15	1997-11-01
1998	1998-02-08	1998-12-27
1999	1999-02-07	1999-12-28
2000	2000-01-26	2000-12-22
2001	2001-01-27	2001-12-25
2002	2002-01-08	2002-12-05
2003	2003-01-31	2003-12-22
2004	2004-03-30	2004-12-01
2005	2005-02-03	2005-12-24
2006	2006-01-01	2006-11-05
2007	2007-01-07	2007-12-23
2008	2008-04-12	2008-12-14
2009	2009-01-24	2009-12-18
2010	2010-01-17	2010-12-19
2011	2011-01-11	2011-12-19
2012	2012-01-11	2012-12-20
2013	2013-02-01	2013-12-22
2014	2014-03-22	2014-11-21
2015	2015-01-09	2015-12-25
2016	2016-01-31	2016-12-29
2017	2017-01-20	2017-10-30
2018	2018-02-24	2018-12-15

Every Fixed Threshold

Fixed thresholds at Harwell
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
10 mm (0.39 in): Days with 10 mm or more rain	78	47	1992	33
25 mm (0.98 in): Days with 25 mm or more rain	73	13	1952	3
50 mm (1.97 in): Days with 50 mm or more rain	21	4	1952	2
100 mm (3.94 in): Days with 100 mm or more rain	2	1	1946	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1941.

Download the Data

Data for Harwell 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 2026-10-16 (16 October 2026). Threshold counts are computed by this site.

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

Harwell Threshold Days by Year

Key Facts for Harwell Thresholds

Days with 10 mm (0.39 in) or more of precipitation

Every Fixed Threshold

Download the Data

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