San Mateo Threshold Days by Year (USC00047864)

10 fixed thresholds counted per year at San Mateo (USC00047864): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for San Mateo Thresholds

San Mateo: days with 10 mm (0.39 in) or more of precipitation in 46 years, most in 1909 with 30.
San Mateo: days with 25 mm (0.98 in) or more of precipitation in 45 years, most in 1952 with 12.
San Mateo: days with a maximum temperature at or above 30 C (86 F) in 39 years, most in 1978 with 46.
San Mateo: days with a maximum temperature at or above 90 F (32.2 C) in 39 years, most in 1978 with 30.
10 fixed thresholds have at least one qualifying day at San Mateo.

Days at or above 30 C (86 F)

39 years with a qualifying day

Days per year at San Mateo with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 46 in 1978.

Days at or above 30 C (86 F) per year at San Mateo
Year	Days	Decade average
1935	14	14.4
1936	24	14.4
1937	11	14.4
1938	5	14.4
1939	18	14.4
1940	4	15
1941	8	15
1943	21	15
1944	12	15
1946	24	15
1947	26	15
1949	10	15
1950	21	16.3
1951	9	16.3
1952	16	16.3
1953	15	16.3
1954	18	16.3
1955	10	16.3
1956	12	16.3
1957	17	16.3
1958	24	16.3
1959	21	16.3
1960	14	17.7
1961	28	17.7
1962	10	17.7
1963	12	17.7
1964	21	17.7
1965	10	17.7
1966	15	17.7
1967	22	17.7
1968	19	17.7
1969	26	17.7
1970	30	28.9
1971	28	28.9
1972	22	28.9
1973	24	28.9
1974	23	28.9
1975	29	28.9
1978	46	28.9

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

First to last qualifying date each year at San Mateo
Year	First date	Last date
1935	1935-05-20	1935-09-17
1936	1936-05-08	1936-10-09
1937	1937-06-25	1937-10-21
1938	1938-06-15	1938-09-10
1939	1939-04-06	1939-10-30
1940	1940-07-05	1940-10-11
1941	1941-05-11	1941-10-04
1943	1943-05-22	1943-10-14
1944	1944-05-25	1944-09-15
1946	1946-04-23	1946-10-11
1947	1947-04-12	1947-10-04
1949	1949-05-06	1949-10-01
1950	1950-04-18	1950-10-11
1951	1951-05-25	1951-10-07
1952	1952-05-17	1952-10-02
1953	1953-05-05	1953-10-05
1954	1954-04-17	1954-10-14
1955	1955-05-18	1955-09-03
1956	1956-05-15	1956-09-28
1957	1957-04-28	1957-09-08
1958	1958-05-15	1958-10-11
1959	1959-05-07	1959-10-24
1960	1960-04-04	1960-09-25
1961	1961-06-14	1961-10-16
1962	1962-04-12	1962-09-17
1963	1963-07-10	1963-09-26
1964	1964-06-22	1964-10-21
1965	1965-04-26	1965-10-25
1966	1966-04-15	1966-10-31
1967	1967-05-15	1967-11-02
1968	1968-04-09	1968-10-26
1969	1969-05-05	1969-09-25
1970	1970-05-02	1970-10-01
1971	1971-06-15	1971-10-13
1972	1972-03-16	1972-10-06
1973	1973-05-28	1973-10-30
1974	1974-05-26	1974-10-18
1975	1975-05-12	1975-09-24
1978	1978-05-13	1978-10-24

Every Fixed Threshold

Fixed thresholds at San Mateo
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
30 C (86 F): Days	39	46	1978	46
35 C (95 F): Days	34	10	1961	8
40 C (104 F): Days	4	3	1971	3
90 F (32.2 C): Days	39	30	1978	30
100 F (37.8 C): Days	13	4	1972	3
0 C (32 F): Frost days (min	29	32	1949	8
20 C (68 F): Tropical nights (min	10	3	1939	1
10 mm (0.39 in): Days with 10 mm or more rain	46	30	1909	20
25 mm (0.98 in): Days with 25 mm or more rain	45	12	1952	7
50 mm (1.97 in): Days with 50 mm or more rain	16	3	1909	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1935.

Download the Data

Data for San Mateo 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).

San Mateo Threshold Days by Year (USC00047864)

Key Facts for San Mateo Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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