No extremes in Castletroy: its weather tracks the middle of Irish towns
About 1,042 mm of rain falls in a typical year; July afternoons reach 19.8°C and January nights drop to 2.6°C. None of the 15 towns and neighbourhoods of 2,500+ in County Limerick has colder January nights. Warming shows here too: 0.2°C more than in 1981–2010, led by April. Windscreens need scraping on about 18 mornings a year, the nights the air drops below 0°C.
Met Éireann 1991–2020 averages for the town’s own square kilometre.
A year in Castletroy at a glance
Each month’s typical high and low, in °C.
What stands out about Castletroy’s climate
Compared with Irish towns, with its place among towns and neighbourhoods of 2,500+ in County Limerick beside it.
What a year in Castletroy feels like
Typical highs and lows by season and by month, from Met Éireann’s 1991–2020 averages.
18 frosts and 4 days of 25°C a year
Ground frosts, when the grass drops below 0°C, come on about 71 nights a year. Air frosts come mostly from November to March, most of all in January (about 5).
Air frosts by month
Average nights below 0°C
Ground frosts by month
Average nights with the grass below 0°C
Counted from Shannon Airport’s daily readings, 1991–2020, 24 km west of Castletroy: Met Éireann publishes these for its stations only.
About 1,042 mm of rain a year
December is the wettest month and April the driest. 7th wettest of 15 towns and neighbourhoods of 2,500+ in County Limerick. The wettest month brings about 1.8 times the rain of the driest. Shannon Airport records 1 mm or more on about 168 days a year, and 10 mm on about 28.
Rain by month
Millimetres
Sunshine by month
Hours, at Shannon Airport
Heating a home in Castletroy
87% of a year’s heating need falls between October and April. Months averaging under 10°C: November to April.
Degree days add up how far each day’s mean temperature falls below 15.5°C over a year.
Living with Castletroy’s climate
What the averages mean for a garden, a free afternoon and a bad-weather day.
In half of years the last air frost at Shannon Airport comes by 20 March and the first by 18 November: about 243 frost-free days in between.
Highs of 17–27°C with lows of 8°C or more: Jun, Jul, Aug and Sep.
Parks & trails →Averages smooth over storms, floods and heatwaves; Castletroy’s hazards page covers the risks.
Flood & hazards →Met Éireann’s nearest station: Shannon Airport
Shannon Airport is 24 km west of Castletroy, the nearest of the 25 synoptic stations where Met Éireann records the weather around the clock. The station stands 15 m above sea level; Castletroy’s centre, 48 m.
| Month | High | Low | Rain | Air frosts | Sun (hours) |
|---|---|---|---|---|---|
| January | 8.9°C | 3.5°C | 103 mm | 4.5 | 52 |
| February | 9.5°C | 3.4°C | 87 mm | 4.2 | 69 |
| March | 11.1°C | 4.1°C | 77 mm | 2.8 | 111 |
| April | 13.6°C | 5.6°C | 62 mm | 0.8 | 162 |
| May | 16.2°C | 8.1°C | 63 mm | 0.0 | 183 |
| June | 18.5°C | 10.7°C | 69 mm | 0.0 | 165 |
| July | 19.6°C | 12.6°C | 76 mm | 0.0 | 135 |
| August | 19.4°C | 12.4°C | 88 mm | 0.0 | 143 |
| September | 17.7°C | 10.6°C | 77 mm | 0.0 | 118 |
| October | 14.4°C | 8.0°C | 95 mm | 0.4 | 93 |
| November | 11.2°C | 5.5°C | 107 mm | 1.6 | 62 |
| December | 9.2°C | 3.9°C | 115 mm | 4.0 | 46 |
| Year | 14.1°C | 7.4°C | 1,020 mm | 18 | 1,338 |
The table is Shannon Airport’s own record, averaged over 1991–2020 from its daily readings (ours, not a Met Éireann table). The temperatures and rain elsewhere on this page are Met Éireann’s 1 km grid at Castletroy itself; the frosts, sunshine and degree days are this station’s.
How Castletroy compares
Against the 321 Irish towns and city neighbourhoods of 2,500 or more, each read from Met Éireann’s grid at its own centre, and its place among towns and neighbourhoods of 2,500+ in County Limerick.
Warmer than it used to be
Castletroy’s 1991–2020 average is 0.2°C warmer than 1981–2010’s. The biggest change is in April (+0.4°C).
A year’s rain is 1,042 mm, up 5% from 992 mm.
Change by month
The two periods share 1991–2010, so the gap is a decade’s step, not the change between two separate 30-year periods.
Castletroy and its neighbours
Every town next door is within half a degree of Castletroy in January and July. Choose a measure to recolour the map; tap a town for its climate.
The towns next door, side by side
The nearest towns of 1,000+ within 19 km: a hill, a valley or the sea can make a real difference over a short distance.
| Town | July high | January low | Rain a year |
|---|---|---|---|
| Castletroy | 19.8°C | 2.6°C | 1,042 mm |
| Annacotty 1.8 km | 20.0°C about the same | 2.7°C about the same | 1,043 mm |
| Garryowen 2.8 km | 20.0°C about the same | 2.9°C about the same | 1,029 mm |
| Westbury 3.5 km | 20.0°C about the same | 2.8°C about the same | 1,086 mm |
| Galvone 3.6 km | 20.0°C about the same | 2.8°C about the same | 1,017 mm |
| Corbally and King's Island 3.8 km | 20.0°C about the same | 2.9°C about the same | 1,056 mm |
| Rathbane 4.1 km | 20.0°C about the same | 2.9°C about the same | 1,006 mm |
Each town’s colour is Met Éireann’s 1 km grid at its own centre, so towns a few kilometres apart can differ.
Castletroy weather by month
Average daily high and low, mean temperature and rain, 1991–2020, for the town itself (Met Éireann’s 1 km grid).
| Month | High | Low | Mean | Rain |
|---|---|---|---|---|
| January | 8.8°C | 2.6°C | 5.7°C | 104 mm |
| February | 9.3°C | 2.5°C | 5.9°C | 86 mm |
| March | 11.0°C | 3.3°C | 7.1°C | 77 mm |
| April | 13.4°C | 4.8°C | 9.1°C | 65 mm |
| May | 16.2°C | 7.3°C | 11.7°C | 66 mm |
| June | 18.6°C | 9.9°C | 14.2°C | 75 mm |
| July | 19.8°C | 11.8°C | 15.8°C | 78 mm |
| August | 19.6°C | 11.5°C | 15.5°C | 90 mm |
| September | 17.7°C | 9.6°C | 13.7°C | 80 mm |
| October | 14.3°C | 7.1°C | 10.7°C | 100 mm |
| November | 11.1°C | 4.5°C | 7.8°C | 109 mm |
| December | 9.1°C | 3.0°C | 6.0°C | 114 mm |
| Year | 14.1°C | 6.5°C | 10.3°C | 1,042 mm |
How much a month can swing
December swings the most: over 30 years its average ranged from 0.7°C (2010) to 9.2°C (2015). September is the most reliable, staying within 3.5°C.
Where Castletroy’s numbers come from
Averages over 30 years, not a forecast: the town’s own from Met Éireann’s grid, the frosts, sunshine and degree days from its nearest station.
- Temperature and rain: Met Éireann’s 1991–2020 averages on its 1 km grid (Climatological Notes 22 and 23), read at the grid point nearest Castletroy’s population centre (0.2 km away).
- Weather station: the nearest of Met Éireann’s 25 synoptic stations, Shannon Airport, 24 km west, from Met Éireann’s station list.
- Frosts, sunshine, degree days: Shannon Airport’s daily readings from Met Éireann (clidata.met.ie), 1991–2020, averaged by month: a month counts when 27 or more of its days were read (rain and sunshine: every day), and a figure needs 10 such years.
- Then and now: Met Éireann’s 1981–2010 averages on the same 1 km grid, at the same point.
- Altitudes: the town’s ground from the Copernicus GLO-30 surface model (a few metres high in built-up places), the station’s from Met Éireann.
- Comparisons: every Irish town and city neighbourhood of 2,500 or more, read the same way; the five city totals are left out.
- Not on this page: snow and wind. Met Éireann publishes neither on a grid; the frosts and sunshine here are its nearest station’s, not the town’s own.
Met Éireann 30-year averages · Met Éireann open data. Under Creative Commons Attribution 4.0 (CC BY 4.0).
Questions about Castletroy’s climate
How warm does Castletroy get in summer?
The warmest month is July, when afternoons average 19.8°C.
How cold does Castletroy get in winter?
February nights average 2.5°C, the coldest of the year. At Shannon Airport, the nearest Met Éireann station, the air drops below 0°C on about 18 nights a year (1991–2020).
How much rain does Castletroy get?
About 1,042 mm a year, more than 64% of Irish towns. December is the wettest month (114 mm) and April the driest (65 mm).
How sunny is it?
Shannon Airport, 24 km west, averages about 1,338 hours of sunshine a year (1991–2020, from its daily record). Met Éireann publishes no sunshine figure for the town itself.
Are these figures for Castletroy itself?
Partly. The temperatures and rain are Met Éireann’s 1991–2020 averages on its 1 km grid, read at Castletroy’s population centre; the frosts, degree days and year-to-year swings are those of Shannon Airport, 24 km west, the nearest of its synoptic stations.
Where do these figures come from?
Met Éireann’s 1991–2020 climate averages, published as maps of Ireland in 1 km squares (Climatological Notes 22 and 23); the page reads the square at Castletroy’s population centre. They are 30-year averages, not a forecast.
Copyright Met Éireann. Source: www.met.ie. This data is published under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Met Éireann does not accept any liability whatsoever for any error or omission in the data, their availability, or for any loss or damage arising from their use. This material has been modified from the original: TownRatings reads the 1 km grid at each town’s population centre. Today’s forecast for Castletroy →
Contains Central Statistics Office (CSO) data, Census 2022, and Tailte Éireann boundaries (CSO Urban Areas, Small Areas, local electoral areas, constituencies), under Creative Commons Attribution 4.0 (CC BY 4.0).