Royal Observatory Threshold Days by Year (SF000208660)

3 fixed thresholds counted per year at Royal Observatory (SF000208660): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Royal Observatory Thresholds

Royal Observatory: days with 10 mm (0.39 in) or more of precipitation in 125 years, most in 1892 with 42.
Royal Observatory: days with 25 mm (0.98 in) or more of precipitation in 120 years, most in 1889 with 12.
Royal Observatory: days with 50 mm (1.97 in) or more of precipitation in 35 years, most in 1859 with 2.
3 fixed thresholds have at least one qualifying day at Royal Observatory.

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

125 years with a qualifying day

Days per year at Royal Observatory with 10 mm (0.39 in) or more of precipitation, with the decade average as a line. The most was 42 in 1892.

Days with 10 mm (0.39 in) or more of precipitation per year at Royal Observatory
Year	Days	Decade average
1850	30	21.3
1851	18	21.3
1852	13	21.3
1853	18	21.3
1854	18	21.3
1855	22	21.3
1856	19	21.3
1857	20	21.3
1858	23	21.3
1859	32	21.3
1860	25	19.6
1861	21	19.6
1862	34	19.6
1863	21	19.6
1864	13	19.6
1865	10	19.6
1866	12	19.6
1867	20	19.6
1868	16	19.6
1869	24	19.6
1870	24	22.7
1871	17	22.7
1872	24	22.7
1873	21	22.7
1874	29	22.7
1875	22	22.7
1876	21	22.7
1877	30	22.7
1879	16	22.7
1881	19	24.2
1882	20	24.2
1883	32	24.2
1884	29	24.2
1885	24	24.2
1886	21	24.2
1887	22	24.2
1888	26	24.2
1889	25	24.2
1890	19	21.5
1891	25	21.5
1892	42	21.5
1893	18	21.5
1894	14	21.5
1895	16	21.5
1896	18	21.5
1897	14	21.5
1898	22	21.5
1899	27	21.5
1900	14	21.4
1901	20	21.4
1902	28	21.4
1903	23	21.4
1904	33	21.4
1905	24	21.4
1906	16	21.4
1907	16	21.4
1908	18	21.4
1909	22	21.4
1910	20	19.2
1911	23	19.2
1912	23	19.2
1913	19	19.2
1914	19	19.2
1915	23	19.2
1916	13	19.2
1917	16	19.2
1918	20	19.2
1919	16	19.2
1920	23	18
1921	21	18
1922	20	18
1923	21	18
1924	12	18
1925	21	18
1926	15	18
1927	17	18
1928	11	18
1929	19	18
1930	13	16.8
1931	16	16.8
1932	21	16.8
1933	20	16.8
1934	14	16.8
1935	17	16.8
1936	11	16.8
1937	22	16.8
1938	17	16.8
1939	17	16.8
1940	19	20.9
1941	32	20.9
1942	18	20.9
1943	18	20.9
1944	32	20.9
1945	20	20.9
1946	18	20.9
1947	18	20.9
1948	17	20.9
1949	17	20.9
1950	22	22.3
1951	22	22.3
1952	21	22.3
1953	20	22.3
1954	26	22.3
1955	20	22.3
1956	25	22.3
1957	28	22.3
1958	16	22.3
1959	23	22.3
1960	15	17.9
1961	21	17.9
1963	16	17.9
1964	15	17.9
1965	19	17.9
1966	19	17.9
1967	21	17.9
1969	17	17.9
1970	21	18.3
1971	13	18.3
1972	14	18.3
1973	11	18.3
1974	25	18.3
1975	22	18.3
1976	22	18.3
1986	19	22
1989	25	22

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

First to last qualifying date each year at Royal Observatory
Year	First date	Last date
1850	1850-01-01	1850-11-20
1851	1851-04-30	1851-11-01
1852	1852-03-22	1852-11-10
1853	1853-01-18	1853-10-06
1854	1854-03-23	1854-10-06
1855	1855-04-15	1855-10-24
1856	1856-03-05	1856-12-27
1857	1857-04-03	1857-12-18
1858	1858-02-26	1858-12-16
1859	1859-01-18	1859-11-27
1860	1860-01-15	1860-12-08
1861	1861-01-15	1861-11-15
1862	1862-04-29	1862-11-12
1863	1863-02-07	1863-11-19
1864	1864-05-18	1864-10-19
1865	1865-04-13	1865-10-25
1866	1866-02-02	1866-09-05
1867	1867-02-01	1867-10-31
1868	1868-04-15	1868-12-13
1869	1869-04-03	1869-12-14
1870	1870-01-20	1870-12-21
1871	1871-03-29	1871-12-18
1872	1872-03-25	1872-12-27
1873	1873-03-10	1873-12-03
1874	1874-03-02	1874-11-09
1875	1875-02-19	1875-12-24
1876	1876-03-07	1876-12-01
1877	1877-02-06	1877-12-02
1879	1879-01-30	1879-12-11
1881	1881-03-31	1881-11-16
1882	1882-03-27	1882-12-28
1883	1883-01-19	1883-10-11
1884	1884-01-14	1884-11-26
1885	1885-01-10	1885-12-09
1886	1886-03-09	1886-12-10
1887	1887-01-03	1887-11-11
1888	1888-03-24	1888-12-27
1889	1889-02-21	1889-12-16
1890	1890-02-08	1890-11-16
1891	1891-02-23	1891-12-07
1892	1892-01-24	1892-12-17
1893	1893-04-30	1893-10-29
1894	1894-02-21	1894-11-22
1895	1895-03-16	1895-11-24
1896	1896-01-06	1896-11-03
1897	1897-02-15	1897-10-02
1898	1898-01-29	1898-11-05
1899	1899-03-23	1899-12-30
1900	1900-02-24	1900-10-13
1901	1901-01-15	1901-11-19
1902	1902-02-24	1902-10-30
1903	1903-01-24	1903-10-26
1904	1904-04-01	1904-12-08
1905	1905-03-09	1905-12-31
1906	1906-04-03	1906-12-24
1907	1907-03-17	1907-12-31
1908	1908-01-13	1908-10-04
1909	1909-01-02	1909-12-26
1910	1910-03-27	1910-11-10
1911	1911-02-14	1911-11-30
1912	1912-03-25	1912-11-23
1913	1913-02-09	1913-12-17
1914	1914-01-20	1914-11-06
1915	1915-03-16	1915-11-13
1916	1916-04-22	1916-09-19
1917	1917-05-03	1917-09-21
1918	1918-02-04	1918-11-18
1919	1919-01-13	1919-11-15
1920	1920-04-10	1920-12-18
1921	1921-02-02	1921-11-10
1922	1922-01-10	1922-10-06
1923	1923-04-06	1923-11-13
1924	1924-04-29	1924-10-24
1925	1925-01-13	1925-11-27
1926	1926-02-25	1926-10-31
1927	1927-02-06	1927-11-12
1928	1928-06-11	1928-09-09
1929	1929-02-21	1929-12-31
1930	1930-01-27	1930-11-30
1931	1931-02-11	1931-10-18
1932	1932-02-12	1932-12-17
1933	1933-01-20	1933-11-01
1934	1934-01-24	1934-10-20
1935	1935-04-27	1935-11-08
1936	1936-01-02	1936-12-04
1937	1937-01-19	1937-09-11
1938	1938-01-12	1938-12-30
1939	1939-02-16	1939-12-31
1940	1940-02-08	1940-11-19
1941	1941-01-07	1941-12-22
1942	1942-04-02	1942-09-16
1943	1943-01-20	1943-10-31
1944	1944-01-09	1944-12-10
1945	1945-04-26	1945-10-04
1946	1946-04-04	1946-12-22
1947	1947-03-14	1947-09-22
1948	1948-03-18	1948-10-11
1949	1949-04-23	1949-11-01
1950	1950-04-10	1950-11-06
1951	1951-01-11	1951-11-26
1952	1952-04-02	1952-11-17
1953	1953-04-09	1953-11-07
1954	1954-01-08	1954-10-25
1955	1955-02-17	1955-12-27
1956	1956-04-09	1956-12-26
1957	1957-02-21	1957-10-26
1958	1958-02-18	1958-11-18
1959	1959-03-03	1959-12-03
1960	1960-04-05	1960-12-19
1961	1961-01-28	1961-12-21
1963	1963-01-16	1963-11-01
1964	1964-05-11	1964-11-05
1965	1965-01-11	1965-12-16
1966	1966-02-15	1966-11-17
1967	1967-01-20	1967-11-22
1969	1969-01-08	1969-10-08
1970	1970-02-23	1970-10-07
1971	1971-05-18	1971-09-05
1972	1972-04-28	1972-09-20
1973	1973-05-28	1973-11-05
1974	1974-01-04	1974-11-03
1975	1975-01-31	1975-11-17
1976	1976-03-06	1976-12-30
1986	1986-01-13	1986-11-02
1989	1989-02-26	1989-11-17

Every Fixed Threshold

Fixed thresholds at Royal Observatory
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	125	42	1892	25
25 mm (0.98 in): Days with 25 mm or more rain	120	12	1889	6
50 mm (1.97 in): Days with 50 mm or more rain	35	2	1859	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1850.

Download the Data

Data for Royal Observatory 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 2025-12-31. Last revised 31 December 2025 (2025-12-31).

Royal Observatory Threshold Days by Year (SF000208660)

Key Facts for Royal Observatory Thresholds

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

Every Fixed Threshold

Download the Data

Related