County Mayo climate

Monthly averages for Castlebar, 2021–2025 · Connacht

Mayo meets the Atlantic head on, from Achill to Belmullet, and is among the wettest and windiest counties. Winters are mild but stormy; the east of the county around Ballina and Claremorris is noticeably drier.

Rain: about 1442 mm falls in a year at Castlebar, on roughly 209 days, making Mayo the 3rd wettest of the 32 counties. October is the wettest month (172 mm) and April the driest (87 mm).

Temperature: August is the warmest month, with afternoons averaging 18°C, and January the coldest, with nights averaging 3°C. Frost is rare.

Sunshine: about 2280 hours a year, the 28th sunniest of the 32 counties. May is the sunniest month (9.7 hours a day) and December the dullest (2.8).

Compare Mayo with its neighbours →

Rainfall

Average total rainfall each month, in millimetres. 1442 mm a year.

Temperature

Bars run from the average night-time low to the average daytime high, in °C.

Sunshine

Hours of sunshine on an average day in each month. About 2280 hours a year.

Mayo and its neighbours
County	Rain mm/yr	Rain days	July high	January low	Sun h/yr
Mayo	1442	209	18°C	3°C	2280
Galway	1424	198	19°C	3°C	2451
Roscommon	1176	184	19°C	3°C	2326
Sligo	1670	237	18°C	2°C	2268

Recent extremes, 2021–2025

Hottest day: 27.7°C on 22 July 2021
Coldest night: −3.4°C on 17 January 2023
Wettest day: 42.0 mm on 2 October 2025
Wettest month: October 2022, 220 mm
Driest month: April 2021, 34 mm

Ireland's all-time records are on the records page.

Castlebar month by month
Month	High °C	Low °C	Rain mm	Rain days	Sun h/day	Wind km/h
January	8	3	114	15	3.3	16
February	9	5	132	18	4.2	20
March	11	4	113	16	5.6	16
April	13	5	87	15	8.1	15
May	15	8	93	15	9.7	13
June	17	11	113	19	8.8	15
July	18	12	102	18	8.4	13
August	18	12	131	20	8.7	15
September	17	11	114	16	6.9	14
October	14	9	172	20	4.7	16
November	11	6	130	17	3.6	16
December	9	5	141	18	2.8	18
Year	13	8	1442	209	2280 h	15

Figures are averages for 2021–2025 at each county town, from the ERA5 weather reanalysis via Open-Meteo. They describe typical lowland weather in each county; hills and exposed coasts are wetter and windier.