Portola Threshold Days by Year (USC00047085)

19 fixed thresholds counted per year at Portola (USC00047085): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Portola Thresholds

Portola: days with a maximum temperature at or above 30 C (86 F) in 88 years, most in 2021 with 77.
Portola: days with a maximum temperature at or above 90 F (32.2 C) in 88 years, most in 2021 with 59.
Portola: nights with a minimum temperature at or below 0 C (32 F) in 88 years, most in 1924 with 305.
Portola: nights with a minimum temperature at or below -10 C (14 F) in 88 years, most in 1928 with 79.
19 fixed thresholds have at least one qualifying day at Portola.

Days at or above 30 C (86 F)

88 years with a qualifying day

Days per year at Portola with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 77 in 2021.

Days at or above 30 C (86 F) per year at Portola
Year	Days	Decade average
1915	46	46.2
1916	8	46.2
1917	59	46.2
1918	60	46.2
1919	58	46.2
1920	16	37.3
1922	29	37.3
1923	55	37.3
1924	51	37.3
1925	28	37.3
1927	32	37.3
1928	50	37.3
1930	18	52
1931	54	52
1932	61	52
1933	55	52
1935	63	52
1936	52	52
1937	57	52
1938	47	52
1939	61	52
1940	67	45.6
1941	34	45.6
1942	42	45.6
1945	61	45.6
1946	47	45.6
1947	36	45.6
1948	41	45.6
1949	37	45.6
1950	41	47.3
1951	65	47.3
1952	40	47.3
1953	50	47.3
1954	42	47.3
1955	59	47.3
1956	35	47.3
1957	40	47.3
1958	44	47.3
1959	57	47.3
1960	53	44.1
1961	43	44.1
1962	48	44.1
1963	25	44.1
1964	24	44.1
1965	16	44.1
1966	57	44.1
1967	65	44.1
1968	54	44.1
1969	56	44.1
1976	41	46.5
1979	52	46.5
1980	46	35.2
1985	44	35.2
1986	31	35.2
1987	31	35.2
1988	51	35.2
1989	8	35.2
1990	27	33.4
1991	37	33.4
1992	43	33.4
1993	17	33.4
1994	44	33.4
1995	27	33.4
1996	50	33.4
1997	22	33.4
1998	34	33.4
2000	44	47.4
2001	46	47.4
2002	46	47.4
2003	57	47.4
2004	33	47.4
2006	50	47.4
2007	45	47.4
2008	54	47.4
2009	52	47.4
2010	39	55.6
2013	49	55.6
2014	58	55.6
2015	54	55.6
2016	57	55.6
2017	71	55.6
2018	61	55.6
2020	68	55.2
2021	77	55.2
2023	36	55.2
2024	66	55.2
2025	51	55.2
2026	33	55.2

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

First to last qualifying date each year at Portola
Year	First date	Last date
1915	1915-07-21	1915-09-17
1916	1916-07-17	1916-07-24
1917	1917-06-23	1917-08-31
1918	1918-06-30	1918-10-02
1919	1919-07-03	1919-09-25
1920	1920-07-02	1920-09-19
1922	1922-07-02	1922-09-03
1923	1923-06-04	1923-09-22
1924	1924-05-12	1924-07-16
1925	1925-05-05	1925-07-31
1927	1927-06-22	1927-08-17
1928	1928-05-29	1928-09-22
1930	1930-06-07	1930-07-18
1931	1931-06-04	1931-09-03
1932	1932-06-22	1932-09-23
1933	1933-05-28	1933-10-05
1935	1935-06-04	1935-09-26
1936	1936-05-26	1936-09-26
1937	1937-05-23	1937-09-17
1938	1938-06-03	1938-09-17
1939	1939-06-11	1939-09-23
1940	1940-05-21	1940-09-02
1941	1941-06-10	1941-09-06
1942	1942-06-29	1942-09-01
1945	1945-06-17	1945-09-15
1946	1946-06-19	1946-09-25
1947	1947-04-30	1947-09-24
1948	1948-06-27	1948-09-14
1949	1949-05-01	1949-09-24
1950	1950-05-30	1950-09-04
1951	1951-05-25	1951-09-20
1952	1952-06-04	1952-10-04
1953	1953-07-02	1953-09-21
1954	1954-05-16	1954-09-27
1955	1955-06-06	1955-09-12
1956	1956-06-25	1956-09-17
1957	1957-06-04	1957-09-11
1958	1958-06-16	1958-10-04
1959	1959-06-18	1959-09-12
1960	1960-06-02	1960-09-26
1961	1961-06-13	1961-08-23
1962	1962-06-19	1962-09-23
1963	1963-06-18	1963-10-02
1964	1964-06-23	1964-10-04
1965	1965-06-10	1965-08-09
1966	1966-05-24	1966-09-29
1967	1967-05-21	1967-09-28
1968	1968-06-16	1968-09-26
1969	1969-06-02	1969-09-11
1976	1976-05-13	1976-09-10
1979	1979-06-03	1979-10-04
1980	1980-05-21	1980-10-08
1985	1985-06-13	1985-08-26
1986	1986-05-29	1986-09-06
1987	1987-06-13	1987-09-23
1988	1988-06-18	1988-09-08
1989	1989-07-06	1989-07-27
1990	1990-06-21	1990-09-11
1991	1991-06-10	1991-09-26
1992	1992-05-25	1992-09-30
1993	1993-06-19	1993-09-11
1994	1994-06-11	1994-09-28
1995	1995-06-25	1995-09-20
1996	1996-06-03	1996-10-10
1997	1997-07-04	1997-08-16
1998	1998-07-07	1998-09-05
2000	2000-05-24	2000-09-21
2001	2001-05-23	2001-09-20
2002	2002-06-06	2002-09-24
2003	2003-05-24	2003-09-29
2004	2004-06-23	2004-09-27
2006	2006-05-16	2006-09-13
2007	2007-06-14	2007-09-11
2008	2008-05-16	2008-09-16
2009	2009-05-16	2009-09-27
2010	2010-06-27	2010-10-01
2013	2013-06-05	2013-09-15
2014	2014-06-06	2014-10-07
2015	2015-06-09	2015-10-14
2016	2016-06-04	2016-09-29
2017	2017-05-25	2017-09-12
2018	2018-06-13	2018-09-28
2020	2020-05-27	2020-10-04
2021	2021-06-01	2021-09-26
2023	2023-07-01	2023-08-31
2024	2024-06-07	2024-10-03
2025	2025-05-31	2025-09-25
2026	2026-06-05	2026-10-08

Every Fixed Threshold

Fixed thresholds at Portola
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
30 C (86 F): Days	88	77	2021	33
35 C (95 F): Days	77	26	1924	10
40 C (104 F): Days	2	5	1924	1
90 F (32.2 C): Days	88	59	2021	27
100 F (37.8 C): Days	20	10	1924	1
110 F (43.3 C): Days	1	2	1924	2
0 C (32 F): Ice days (max	78	34	1933	4
0 C (32 F): Frost days (min	88	305	1924	108
-10 C (14 F): Days with min	88	79	1928	7
-20 C (-4 F): Days with min	48	18	1917	6
-30 C (-22 F): Days with min	3	1	1924	1
20 C (68 F): Tropical nights (min	2	3	1916	3
10 mm (0.39 in): Days with 10 mm or more rain	84	34	1996	9
25 mm (0.98 in): Days with 25 mm or more rain	83	15	1996	3
50 mm (1.97 in): Days with 50 mm or more rain	34	6	2017	1
100 mm (3.94 in): Days with 100 mm or more rain	2	1	1955	1
10 cm (3.9 in): Days with 10 cm or more snowfall	52	16	1952	3
25 cm (9.8 in): Days with 25 cm or more snowfall	35	7	1952	1
50 cm (19.7 in): Days with 50 cm or more snowfall	13	2	1967	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1915.

Download the Data

Data for Portola 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).

Portola Threshold Days by Year (USC00047085)

Key Facts for Portola Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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