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Data as of 2025-12-31
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Built 2026-10-19 (19 October 2026)

Heathrow Threshold Days by Year (UKM00003772)

7 fixed thresholds counted per year at Heathrow (UKM00003772): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Heathrow Thresholds

  • Heathrow: days with 10 mm (0.39 in) or more of precipitation in 25 years, most in 2024 with 23.
  • Heathrow: days with 25 mm (0.98 in) or more of precipitation in 22 years, most in 1975 with 3.
  • Heathrow: days with a maximum temperature at or above 30 C (86 F) in 6 years, most in 1976 with 21.
  • Heathrow: days with a maximum temperature at or below 0 C (32 F) in 6 years, most in 1979 with 4.
  • 7 fixed thresholds have at least one qualifying day at Heathrow.
6 years with a qualifying day
Days at or above 30 C (86 F) per year at Heathrow Days per year at Heathrow with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 21 in 1976. 01020301975: 61976: 211979: 11997: 32023: 102024: 5197519761979199720232024
Days per year at Heathrow with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 21 in 1976.
Days at or above 30 C (86 F) per year at Heathrow
YearDaysDecade average
197569.3
1976219.3
197919.3
199733
2023107.5
202457.5
First to last qualifying date each year at Heathrow For each year, a bar from the first to the last day at Heathrow meeting 30 C (86 F). 1975: 29 July 1975 to 8 August 19751976: 8 June 1976 to 25 August 19761979: 27 July 1979 to 27 July 19791997: 8 August 1997 to 19 August 19972023: 10 June 2023 to 10 September 20232024: 26 June 2024 to 12 August 2024197519761979199720232024JanFebMarAprMayJunJulAugSepOctNovDec
For each year, a bar from the first to the last day at Heathrow meeting 30 C (86 F).
First to last qualifying date each year at Heathrow
YearFirst dateLast date
19751975-07-291975-08-08
19761976-06-081976-08-25
19791979-07-271979-07-27
19971997-08-081997-08-19
20232023-06-102023-09-10
20242024-06-262024-08-12

Every Fixed Threshold

Fixed thresholds at Heathrow
ThresholdYears with a qualifying dayMost days in a yearYearLatest year days
30 C (86 F): Days62119765
35 C (95 F): Days1119761
90 F (32.2 C): Days4919761
0 C (32 F): Ice days (max6419793
10 mm (0.39 in): Days with 10 mm or more rain2523202423
25 mm (0.98 in): Days with 25 mm or more rain22319751
50 mm (1.97 in): Days with 50 mm or more rain1119811

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1975.

Download the Data

  • Data for Heathrow 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).