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Data as of 2025-12-31
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Built 2026-10-16 (16 October 2026)

Mount Wilson Threshold Days by Year

3 fixed thresholds counted per year at Mount Wilson (ASN00023906): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Mount Wilson Thresholds

  • Mount Wilson: days with 10 mm (0.39 in) or more of precipitation in 22 years, most in 1999 with 30.
  • Mount Wilson: days with 25 mm (0.98 in) or more of precipitation in 21 years, most in 1995 with 8.
  • Mount Wilson: days with 50 mm (1.97 in) or more of precipitation in 3 years, most in 1986 with 2.
  • 3 fixed thresholds have at least one qualifying day at Mount Wilson.
22 years with a qualifying day
Days with 10 mm (0.39 in) or more of precipitation per year at Mount Wilson Days per year at Mount Wilson with 10 mm (0.39 in) or more of precipitation, with the decade average as a line. The most was 30 in 1999. 01020301984: 171985: 191986: 221987: 231994: 131995: 261999: 302000: 262002: 152003: 262006: 132007: 242008: 102009: 262010: 242011: 212012: 202013: 212014: 152015: 152017: 232018: 1619841987199920032008201120142018
Days per year at Mount Wilson with 10 mm (0.39 in) or more of precipitation, with the decade average as a line. The most was 30 in 1999.
Days with 10 mm (0.39 in) or more of precipitation per year at Mount Wilson
YearDaysDecade average
19841720.3
19851920.3
19862220.3
19872320.3
19941323
19952623
19993023
20002620
20021520
20032620
20061320
20072420
20081020
20092620
20102419.4
20112119.4
20122019.4
20132119.4
20141519.4
20151519.4
20172319.4
20181619.4
First to last qualifying date each year at Mount Wilson For each year, a bar from the first to the last day at Mount Wilson meeting 10 mm (0.39 in). 1984: 11 March 1984 to 10 November 19841985: 5 April 1985 to 8 December 19851986: 16 April 1986 to 7 December 19861987: 20 February 1987 to 9 December 19871994: 6 January 1994 to 2 November 19941995: 14 January 1995 to 23 October 19951999: 7 March 1999 to 3 December 19992000: 20 February 2000 to 19 October 20002002: 2 January 2002 to 5 December 20022003: 30 January 2003 to 22 December 20032006: 29 January 2006 to 12 November 20062007: 7 January 2007 to 22 December 20072008: 27 April 2008 to 13 December 20082009: 4 March 2009 to 29 November 20092010: 7 March 2010 to 19 December 20102011: 14 January 2011 to 18 December 20112012: 8 January 2012 to 6 November 20122013: 31 March 2013 to 20 September 20132014: 14 February 2014 to 16 November 20142015: 13 January 2015 to 4 November 20152017: 13 January 2017 to 19 December 20172018: 14 April 2018 to 14 December 201819841987199920032008201120142018JanFebMarAprMayJunJulAugSepOctNovDec
For each year, a bar from the first to the last day at Mount Wilson meeting 10 mm (0.39 in).
First to last qualifying date each year at Mount Wilson
YearFirst dateLast date
19841984-03-111984-11-10
19851985-04-051985-12-08
19861986-04-161986-12-07
19871987-02-201987-12-09
19941994-01-061994-11-02
19951995-01-141995-10-23
19991999-03-071999-12-03
20002000-02-202000-10-19
20022002-01-022002-12-05
20032003-01-302003-12-22
20062006-01-292006-11-12
20072007-01-072007-12-22
20082008-04-272008-12-13
20092009-03-042009-11-29
20102010-03-072010-12-19
20112011-01-142011-12-18
20122012-01-082012-11-06
20132013-03-312013-09-20
20142014-02-142014-11-16
20152015-01-132015-11-04
20172017-01-132017-12-19
20182018-04-142018-12-14

Every Fixed Threshold

Fixed thresholds at Mount Wilson
ThresholdYears with a qualifying dayMost days in a yearYearLatest year days
10 mm (0.39 in): Days with 10 mm or more rain2230199916
25 mm (0.98 in): Days with 25 mm or more rain21819951
50 mm (1.97 in): Days with 50 mm or more rain3219861

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1984.

Download the Data

  • Data for Mount Wilson 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 2026-10-14 (14 October 2026). Threshold counts are computed by this site.

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