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Built 2026-10-19 (19 October 2026)

Palo Alto Threshold Days by Year (USC00046642)

9 fixed thresholds counted per year at Palo Alto (USC00046642): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Palo Alto Thresholds

  • Palo Alto: days with 10 mm (0.39 in) or more of precipitation in 29 years, most in 1940 with 27.
  • Palo Alto: days with a maximum temperature at or above 30 C (86 F) in 28 years, most in 1926 with 26.
  • Palo Alto: days with a maximum temperature at or above 90 F (32.2 C) in 28 years, most in 1929 with 14.
  • Palo Alto: nights with a minimum temperature at or below 0 C (32 F) in 27 years, most in 1949 with 37.
  • 9 fixed thresholds have at least one qualifying day at Palo Alto.
28 years with a qualifying day
Days at or above 30 C (86 F) per year at Palo Alto Days per year at Palo Alto with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 26 in 1926. 01020301923: 151924: 121925: 121926: 261927: 121928: 141929: 241932: 141933: 121934: 221935: 201936: 241937: 131938: 101939: 201940: 71941: 101942: 71943: 161944: 91945: 151946: 161947: 201948: 101949: 101950: 171951: 91952: 171923192619291934193719401943194619491952
Days per year at Palo Alto with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 26 in 1926.
Days at or above 30 C (86 F) per year at Palo Alto
YearDaysDecade average
19231516.4
19241216.4
19251216.4
19262616.4
19271216.4
19281416.4
19292416.4
19321416.9
19331216.9
19342216.9
19352016.9
19362416.9
19371316.9
19381016.9
19392016.9
1940712
19411012
1942712
19431612
1944912
19451512
19461612
19472012
19481012
19491012
19501714.3
1951914.3
19521714.3
First to last qualifying date each year at Palo Alto For each year, a bar from the first to the last day at Palo Alto meeting 30 C (86 F). 1923: 8 May 1923 to 19 October 19231924: 6 April 1924 to 3 October 19241925: 23 June 1925 to 25 August 19251926: 24 April 1926 to 5 October 19261927: 23 April 1927 to 12 October 19271928: 2 June 1928 to 8 October 19281929: 11 May 1929 to 23 October 19291932: 25 May 1932 to 9 September 19321933: 27 May 1933 to 18 October 19331934: 10 May 1934 to 9 October 19341935: 4 May 1935 to 17 September 19351936: 8 May 1936 to 9 October 19361937: 25 June 1937 to 21 October 19371938: 31 May 1938 to 9 September 19381939: 12 May 1939 to 11 October 19391940: 13 May 1940 to 11 October 19401941: 10 May 1941 to 3 October 19411942: 20 May 1942 to 16 September 19421943: 22 May 1943 to 6 October 19431944: 8 June 1944 to 27 September 19441945: 1 May 1945 to 8 September 19451946: 24 April 1946 to 29 September 19461947: 15 April 1947 to 22 September 19471948: 21 June 1948 to 14 September 19481949: 7 May 1949 to 1 October 19491950: 20 April 1950 to 29 September 19501951: 26 May 1951 to 8 October 19511952: 17 May 1952 to 3 October 19521923192719331937194119451949JanFebMarAprMayJunJulAugSepOctNovDec
For each year, a bar from the first to the last day at Palo Alto meeting 30 C (86 F).
First to last qualifying date each year at Palo Alto
YearFirst dateLast date
19231923-05-081923-10-19
19241924-04-061924-10-03
19251925-06-231925-08-25
19261926-04-241926-10-05
19271927-04-231927-10-12
19281928-06-021928-10-08
19291929-05-111929-10-23
19321932-05-251932-09-09
19331933-05-271933-10-18
19341934-05-101934-10-09
19351935-05-041935-09-17
19361936-05-081936-10-09
19371937-06-251937-10-21
19381938-05-311938-09-09
19391939-05-121939-10-11
19401940-05-131940-10-11
19411941-05-101941-10-03
19421942-05-201942-09-16
19431943-05-221943-10-06
19441944-06-081944-09-27
19451945-05-011945-09-08
19461946-04-241946-09-29
19471947-04-151947-09-22
19481948-06-211948-09-14
19491949-05-071949-10-01
19501950-04-201950-09-29
19511951-05-261951-10-08
19521952-05-171952-10-03

Every Fixed Threshold

Fixed thresholds at Palo Alto
ThresholdYears with a qualifying dayMost days in a yearYearLatest year days
30 C (86 F): Days2826192617
35 C (95 F): Days23819291
90 F (32.2 C): Days281419294
100 F (37.8 C): Days8419292
0 C (32 F): Frost days (min273719495
20 C (68 F): Tropical nights (min1119391
10 mm (0.39 in): Days with 10 mm or more rain2927194019
25 mm (0.98 in): Days with 25 mm or more rain22919406
50 mm (1.97 in): Days with 50 mm or more rain2119501

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1923.

Download the Data

  • Data for Palo Alto 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 . Last revised (2025-12-31).