Isle of Man · 1991–2020

Best time to visit
Castletown.

July leads for comfortable weather in Castletown: typically 18.2°C by day, 12.5°C at night, with 59 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortJuly

Typical high18.2°C

Typical low12.5°C

Rain in July59 mm

Comfort

July

July · August · June

67climate match

Beach

July

July · August · June

32climate match

Outdoors

July

July · June · August

78climate match

The weakest month is January, scoring 13 against July’s 67 — days reach only 8.5°C, 15° below the 24°C the score treats as ideal.

Month by month

The whole year,
without the guesswork.

The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.

Jan

138.5° / 4.1°

Feb

178.4° / 3.8°

Mar

229.5° / 4.5°

Apr

3311.6° / 5.8°

May

4714.4° / 8.1°

Jun

5816.6° / 10.6°

Jul

6718.2° / 12.5°

Aug

6518.1° / 12.7°

Sep

5616.5° / 11.4°

Oct

3713.8° / 9.2°

Nov

2111.1° / 6.6°

Dec

149.3° / 4.7°

Monthly climate evidence for Castletown — daylight is calculated from latitude, everything else is measured, sea temperature from the nearest open water 6 km away
Month	Day	Night	Rain	Wet days	Sea	Daylight	Comfort	Coverage
January	8.5°C	4.1°C	83 mm	14.2	8.9°C	7 h 54	13	Strong coverage
February	8.4°C	3.8°C	66 mm	11.4	8.0°C	9 h 39	17	Strong coverage
March	9.5°C	4.5°C	62 mm	10.9	7.8°C	11 h 39	22	Strong coverage
April	11.6°C	5.8°C	55 mm	10	8.5°C	13 h 57	33	Strong coverage
May	14.4°C	8.1°C	55 mm	9.8	10.0°C	15 h 57	47	Strong coverage
June	16.6°C	10.6°C	62 mm	9.3	12.0°C	17 h 07	58	Strong coverage
July	18.2°C	12.5°C	59 mm	10.2	13.8°C	16 h 39	67	Strong coverage
August	18.1°C	12.7°C	67 mm	10.8	14.8°C	14 h 52	65	Strong coverage
September	16.5°C	11.4°C	71 mm	11.2	14.6°C	12 h 37	56	Strong coverage
October	13.8°C	9.2°C	102 mm	13.4	13.7°C	10 h 25	37	Strong coverage
November	11.1°C	6.6°C	105 mm	15.8	12.1°C	8 h 25	21	Strong coverage
December	9.3°C	4.7°C	95 mm	14.7	10.4°C	7 h 23	14	Strong coverage

What has changed

Castletown runs +1.1°C
on the 1961–1990 baseline.

Each bar compares the 2011–2025 daytime average for that month against the same month in 1961–1990, measured at the same station. Months where the older record is too thin to compare are left blank.

Jan

+0.9

Feb

+1.5

Mar

+1.2

Apr

+1.2

May

+1.3

Jun

+0.9

Jul

+1.0

Aug

+0.7

Sep

+1.0

Oct

+0.7

Nov

+1.2

Dec

+1.2

July daytime highs, 2011–2025. Last recorded: 19.5°C.

Records at RONALDSWAY, 1960–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	13.5°C8 Jan 2015	-7.7°C12 Jan 1982	36 mm25 Jan 2013	170 mm2014 · driest 14 mm in 1997	67
February	13.2°C15 Feb 2022	-7.4°C16 Feb 1969	35 mm5 Feb 1996	139 mm1977 · driest 2 mm in 1986	67
March	17.2°C27 Mar 2012	-6.7°C2 Mar 1986	38 mm22 Mar 2013	170 mm2006 · driest 15 mm in 2025	67
April	20.1°C15 Apr 2003	-3.4°C2 Apr 1984	47 mm8 Apr 2024	135 mm2024 · driest 5 mm in 1980	67
May	23.7°C30 May 1978	-1.4°C3 May 1967	30 mm22 May 2024	141 mm1993 · driest 10 mm in 1977	67
June	28.1°C12 Jun 2023	1.4°C5 Jun 1991	55 mm14 Jun 2007	171 mm2012 · driest 12 mm in 2018	67
July	28.9°C11 Jul 1983	4.2°C18 Jul 1965	69 mm2 Jul 1968	149 mm2023 · driest 10 mm in 1989	66
August	27.9°C12 Aug 2022	4.8°C9 Aug 1965	48 mm16 Aug 1963	146 mm2008 · driest 4 mm in 1976	66
September	26.5°C1 Sep 1991	0.6°C22 Sep 1979	48 mm3 Sep 1984	163 mm1968 · driest 3 mm in 1986	66
October	20.3°C10 Oct 1991	-1.9°C27 Oct 1962	78 mm3 Oct 2014	229 mm2002 · driest 24 mm in 1969	66
November	16.2°C1 Nov 2007	-4.5°C22 Nov 1965	36 mm20 Nov 1971	218 mm2002 · driest 34 mm in 1983	66
December	14.2°C11 Dec 2001	-9.1°C31 Dec 1961	52 mm28 Dec 1978	213 mm1978 · driest 18 mm in 1963	66

Typical days per month at RONALDSWAY, 1991–2020
Month	Days 25°C+	Frost nights	Heavy rain (10 mm+)
January	0	3	2
February	0	3	2
March	0	2	1
April	0	<1	1
May	0	0	1
June	<1	0	2
July	<1	0	2
August	<1	0	2
September	0	0	2
October	0	<1	3
November	0	<1	3
December	0	2	3

How often, not how much — every day in RONALDSWAY’s record sorted by what it was actually like, rather than averaged
Month	Warm & dry days	Wet days	Washouts	Week with 3+ wet days	Daytime mean has ranged
January	0%	46%	8%	65%	6.8–9.6°C
February	0%	40%	6%	55%	5.9–9.4°C
March	0%	36%	5%	50%	7.4–10.5°C
April	<1%	33%	5%	43%	9.9–12.4°C
May	3%	31%	4%	40%	12.5–15.8°C
June	9%	32%	5%	42%	15.1–17.9°C
July	14%	30%	5%	40%	16.5–19.7°C
August	11%	34%	7%	47%	16.7–19.4°C
September	2%	38%	8%	57%	15.1–17.1°C
October	0%	45%	10%	63%	12.6–14.9°C
November	0%	50%	11%	70%	9.5–11.9°C
December	0%	47%	9%	66%	7.5–10.4°C

A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.

1960Each stripe is one year’s mean temperature against the 66-year average. Warmest: 2023. Coolest: 1963.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 3042255
NOAA station: UKE00108854 · RONALDSWAY
Station distance: 1.8 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 30 usable years
Daylight: Calculated from latitude 54.07°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Sea temperature: NOAA OISST v2.1 1991–2020 monthly climatology, nearest open water 6 km from the place centre. A sheltered bay can run warmer than the open sea it is measured from.
Important limit: Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.

These places read the same station, so their numbers are identical — distance from RONALDSWAY is what differs

Douglas→Ramsey→Peel→Port Erin→Laxey→Colby→

Or put two places side by side: Castletown vs Douglas

Best time to visitCastletown.

July

July

July

The whole year,without the guesswork.

Castletown runs +1.1°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Castletown.

The whole year,
without the guesswork.

Castletown runs +1.1°C
on the 1961–1990 baseline.

Nearby, measured,
and named.