Few Irish towns have colder winter nights than Castleblayney
The warmest part of a July day comes in at 19.2°C on average. Of all months, December brings the most rain and May the least. Its July afternoons stay fresher than in 92% of Irish towns. An umbrella earns its place on about 171 days a year with 1 mm of rain or more.
Met Éireann 1991–2020 averages for the town’s own square kilometre.
A year in Castleblayney at a glance
Each month’s typical high and low, in °C.
What stands out about Castleblayney’s climate
Compared with Irish towns, with its place among towns of 2,500+ in County Monaghan beside it.
What a year in Castleblayney feels like
Typical highs and lows by season and by month, from Met Éireann’s 1991–2020 averages.
40 frosts and 2 days of 25°C a year
Ground frosts, when the grass drops below 0°C, come on about 88 nights a year. Air frosts come mostly from October to April, most of all in February (about 8).
Air frosts by month
Average nights below 0°C
Ground frosts by month
Average nights with the grass below 0°C
Counted from Ballyhaise’s daily readings, 2003–2020, 38 km west of Castleblayney: Met Éireann publishes these for its stations only. At that distance, read them as the area’s climate.
About 1,045 mm of rain a year
December is the wettest month and May the driest. The wettest of 3 towns of 2,500+ in County Monaghan. The wettest month brings about 1.6 times the rain of the driest. Ballyhaise records 1 mm or more on about 171 days a year, and 10 mm on about 27.
Rain by month
Millimetres
Heating a home in Castleblayney
84% of a year’s heating need falls between October and April. Months averaging under 10°C: October to April.
Degree days add up how far each day’s mean temperature falls below 15.5°C over a year.
Living with Castleblayney’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 Ballyhaise comes by 20 April and the first by 26 October: about 189 frost-free days in between.
Highs of 17–27°C with lows of 8°C or more: Jun, Jul and Aug.
Parks & trails →Averages smooth over storms, floods and heatwaves; Castleblayney’s hazards page covers the risks.
Flood & hazards →Met Éireann’s nearest station: Ballyhaise
Ballyhaise is 38 km west of Castleblayney, the nearest of the 25 synoptic stations where Met Éireann records the weather around the clock. The station stands 78 m above sea level; Castleblayney’s centre, 133 m.
| Month | High | Low | Rain | Air frosts |
|---|---|---|---|---|
| January | 7.6°C | 2.1°C | 100 mm | 7.9 |
| February | 8.0°C | 1.8°C | 76 mm | 8.4 |
| March | 9.8°C | 2.2°C | 79 mm | 7.3 |
| April | 12.6°C | 4.0°C | 60 mm | 2.9 |
| May | 15.3°C | 6.5°C | 66 mm | 0.3 |
| June | 18.0°C | 9.4°C | 70 mm | 0.0 |
| July | 19.1°C | 11.2°C | 92 mm | 0.0 |
| August | 18.2°C | 10.9°C | 104 mm | 0.0 |
| September | 16.5°C | 9.0°C | 81 mm | 0.1 |
| October | 13.4°C | 6.6°C | 96 mm | 1.3 |
| November | 9.7°C | 3.9°C | 98 mm | 4.1 |
| December | 7.8°C | 2.4°C | 99 mm | 7.3 |
| Year | 13.0°C | 5.8°C | 1,022 mm | 40 |
The table is Ballyhaise’s own record, averaged over 2003–2020 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 Castleblayney itself; the frosts and degree days are this station’s.
How Castleblayney 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 of 2,500+ in County Monaghan.
Warmer than it used to be
Castleblayney’s 1991–2020 average is 0.2°C warmer than 1981–2010’s. The biggest change is in February (+0.4°C).
A year’s rain is 1,045 mm, up 4% from 1,001 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.
Castleblayney and its neighbours
Carrickmacross has the warmest July afternoons (19.9°C, 0.7°C warmer). 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 |
|---|---|---|---|
| Castleblayney | 19.2°C | 1.4°C | 1,045 mm |
| Ballybay 10 km | 19.4°C about the same | 1.6°C about the same | 1,005 mm |
| Carrickmacross 16 km | 19.9°C 0.7°C warmer | 2.0°C 0.6°C milder | 931 mm |
Each town’s colour is Met Éireann’s 1 km grid at its own centre, so towns a few kilometres apart can differ.
Castleblayney 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 | 7.3°C | 1.4°C | 4.4°C | 100 mm |
| February | 8.0°C | 1.3°C | 4.7°C | 82 mm |
| March | 9.9°C | 2.3°C | 6.1°C | 77 mm |
| April | 12.4°C | 3.8°C | 8.1°C | 70 mm |
| May | 15.3°C | 6.2°C | 10.7°C | 70 mm |
| June | 17.7°C | 9.0°C | 13.3°C | 72 mm |
| July | 19.2°C | 10.9°C | 15.0°C | 84 mm |
| August | 18.8°C | 10.6°C | 14.7°C | 93 mm |
| September | 16.7°C | 8.7°C | 12.7°C | 78 mm |
| October | 13.2°C | 6.0°C | 9.6°C | 104 mm |
| November | 9.8°C | 3.4°C | 6.6°C | 107 mm |
| December | 7.6°C | 1.6°C | 4.6°C | 110 mm |
| Year | 13.0°C | 5.4°C | 9.2°C | 1,045 mm |
How much a month can swing
December swings the most: over 18 years its average ranged from −1.4°C (2010) to 7.8°C (2015). August is the most reliable, staying within 2.2°C.
Where Castleblayney’s numbers come from
Averages over 30 years, not a forecast: the town’s own from Met Éireann’s grid, the frosts 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 Castleblayney’s population centre (0.2 km away).
- Weather station: the nearest of Met Éireann’s 25 synoptic stations, Ballyhaise, 38 km west, from Met Éireann’s station list.
- Frosts and degree days: Ballyhaise’s daily readings from Met Éireann (clidata.met.ie), 2003–2020, 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: sunshine at this station, snow and wind. Met Éireann publishes none of them on a grid; the frosts 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 Castleblayney’s climate
How warm does Castleblayney get in summer?
The warmest month is July, when afternoons average 19.2°C.
How cold does Castleblayney get in winter?
February nights average 1.3°C, the coldest of the year. At Ballyhaise, the nearest Met Éireann station, the air drops below 0°C on about 40 nights a year (2003–2020).
How much rain does Castleblayney get?
About 1,045 mm a year, more than 65% of Irish towns. December is the wettest month (110 mm) and May the driest (70 mm).
How sunny is it?
Met Éireann publishes its 1991–2020 sunshine averages for its weather stations only, not on the 1 km grid this page reads, so there is no sunshine figure for Castleblayney itself. Its nearest synoptic station is Ballyhaise.
Are these figures for Castleblayney itself?
Partly. The temperatures and rain are Met Éireann’s 1991–2020 averages on its 1 km grid, read at Castleblayney’s population centre; the frosts, degree days and year-to-year swings are those of Ballyhaise, 38 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 Castleblayney’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 Castleblayney →
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).