Castletown weather by month & the best time to visit
Isle of Man · seaside town · oceanic / maritime climate
The best time to visit Castletown is July — its sunniest month (Sunshine Score 48/100), with August and September close behind. Castletown averages about 1,459 hours of sunshine a year. Daytime highs around 16°C / 61°F and roughly 79 mm of rain in July.
When is the best time to visit Castletown?
For sunshine, the best time to visit Castletown is July, then August and September. The dullest month is January (0/100, 110 mm of rain). The full month-by-month picture is in the table below.
How sunny is Castletown?
Castletown isn't a sunny place by world standards: about 1,459 hours of sunshine a year. 48 Sunshine Score points separate July (48) from January (0), so the month you pick matters. It is the only destination Sunshine Atlas tracks in Isle of Man. The year's 1,123 mm of rain spreads fairly evenly across the months, with no pronounced dry season.
Sunshine Score by month
| Month | Score | Day high | Night low | Rain | UV | Sea |
|---|---|---|---|---|---|---|
| January | 0 | 8° / 46°F | 6° / 43°F | 110 mm | 0 | 10° / 50°F |
| February | 0 | 8° / 46°F | 6° / 43°F | 89 mm | 1 | 9° / 48°F |
| March | 0 | 8° / 46°F | 6° / 43°F | 82 mm | 2 | 9° / 48°F |
| April | 6 | 9° / 48°F | 7° / 45°F | 62 mm | 3 | 10° / 50°F |
| May | 25 | 12° / 54°F | 10° / 50°F | 65 mm | 4 | 12° / 54°F |
| June | 37 | 14° / 57°F | 12° / 54°F | 74 mm | 5 | 13° / 55°F |
| July | 48 | 16° / 61°F | 14° / 57°F | 79 mm | 4 | 15° / 59°F |
| August | 46 | 16° / 61°F | 15° / 59°F | 97 mm | 4 | 16° / 61°F |
| September | 41 | 15° / 59°F | 14° / 57°F | 90 mm | 3 | 15° / 59°F |
| October | 32 | 14° / 57°F | 12° / 54°F | 123 mm | 1 | 14° / 57°F |
| November | 16 | 11° / 52°F | 9° / 48°F | 126 mm | 0 | 13° / 55°F |
| December | 5 | 9° / 48°F | 8° / 46°F | 126 mm | 0 | 11° / 52°F |
Sea temperature in Castletown by month
The sea off Castletown is warmest in August at around 16°C / 61°F, and coolest in February at 9°C / 48°F. It never reaches comfortable swimming temperatures (21°C+). Month-by-month sea-surface temperatures are in the Sea column of the table above.
Nearest destinations
Head-to-head
How Castletown compares month by month: Castletown vs Dublin · Castletown vs Liverpool · Castletown vs Belfast · all comparisons
Castletown: questions and answers
What kind of destination is Castletown?
Castletown is a seaside town in Isle of Man with a oceanic / maritime climate — the sea reaches 16°C at its warmest.
How many hours of sunshine does Castletown get a year?
Castletown gets about 1,459 hours of sunshine a year, at its best around July.
When is the best time to visit Castletown?
The sunniest time to visit Castletown is July, when the Sunshine Score peaks at 48/100 (with August and September close behind). Expect daytime highs around 16°C / 61°F.
What is the least sunny month in Castletown?
January is the least sunny month in Castletown, scoring 0/100 with about 110 mm of rain.
What is the sea temperature in Castletown?
The sea in Castletown ranges from about 9°C (February) to 16°C (August). Month-by-month sea temperatures are on this page.
How strong is the sun in Castletown?
The typical midday UV index in Castletown peaks around 5 (moderate) in June, easing to about 0 (low) in January. Month-by-month midday UV values are in the UV column of the table on this page.
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