My house is situated in Newtownabbey, on the east coast of County Antrim, Northern Ireland, at 54.6 degrees north, 5.9 degrees west. We are 65 metres (210ft) above sea level, 2.5 miles from Belfast Lough and the mild ocean current emanating from the Gulf Stream. We therefore have a much milder climate than most areas at this latitude. The growing season near the coast is approximately 280 days (but as low as 235 days inland & at altitude).
This page is intended to give some idea of the type of weather that my plants must endure. I have been unable to find any reliable climate data for my area (most data available on the web covers the whole of N.Ireland and does not reflect the milder climate of the coastal regions). The following is therefore based on personal experience with my own temperature logger (operational since 1995 and now available "live" on this website) and I believe it to be quite accurate:
Average Annual Minimum: -4°C / 25°F
Average Annual Maximum: 26°C / 80°F
Absolute Minimum: -11.6°C / 11.0°F (December 2010)
Absolute Maximum: 31.6°C / 88.9°F (June 2018)
Plenty! About 850mm (33.5 inches) per year, there is a drier period during Spring and early Summer.
Not a strong point! Sunniest months are May and June each with about 6 hours per day on average.
Very little, a few days a year, and virtually always the wet slushy stuff.
First one usually late November / early December, last one usually late March / early April. Not too much frost.
Interesting point (maybe): How is frost defined? A ground frost can occur when the air temperature is less than about 3°C (37°F), although an air frost (by definition) only occurs when the air temperature (measured at 2m above the ground) is at or below 0°C (32°F). And then there is the familiar white covering which is known as a hoar frost. Ground frost and hoar frost can occur even though there is no air frost; ground frost can occur even though there is no hoar frost. The dates above refer to the first & last air frosts as (meteorologically and horticulturally) this is how these dates are usually defined. The earliest ground/hoar frost in recent years has been in late October and the latest in early May.
Some historical climate info:
Northern Ireland's official coldest temperature ever recorded was -18.7°C (-1.7°F) at Castlederg, Co.Tyrone (a cold inland site) on 24th December 2010. By contrast, Helen's Bay in Co.Down (a favoured mild area right on the Co.Down coast) has recorded an extreme minimum of only -5.4°C (22.3°F). Some parts of the North Down coast may not have seen below about -4C (25F). This illustrates perfectly the difference between coastal and inland areas and explains why climate info covering the whole of Northern Ireland is not very useful - even in a small country like ours the moderating influence of the ocean has a huge effect.
Here is a table showing the winter minima at my location since 1995 (when I set up my outside temperature sensor). Some earlier readings are only listed to the nearest degree celsius:
The average in the table above does not include any "so far" figures from a winter still in progress!
Notes from the above table:
- Many winters are zone 9b or high 9a, but an occasional (unwelcome :-) 8b winter lowers the overall average. We sincerely hope 2010/11 is an anomaly as it saw the coldest December for >100 years and multiple all time record lows.
- The coldest temperature most often occurs in January, although winter certainly encompasses the 3-month period Dec-Feb and sometimes continues into early March (when areas at lower latitudes will already be reliably warming up). 2021/22 was another interesting anomaly as an exceptionally mild meteorological winter (nothing below 0C during Dec/Jan/Feb) led to the coldest temperature of the cold season being recorded in April!
- We seem to be a borderline 9a/9b climate, however I would prefer to say that we are a solid 9a rather than marginal 9b.
Finally a note on weather sites on the web:
If there's one thing harder than finding good climate info for my area on the web, it's got to be finding reliable weather forecasts!The situation is more confusing than ever, with everyone wanting to give you their own personal forecast. Some of these sites even try to provide long-range forecasts up to 3 months (or more) ahead. Well the problem is that weather is barely accurately forecastable (if that's a real word) a few days ahead, and even then the experts have problems. Worse still, these 'independent' weather sites can be set up by anyone with a web connection and are often populated by entrenched cold weather fanatics who may be inclined to post what they (and their readers) would like to see happen rather than what is realistically likely to happen. So what do you do if you grow exotic plants, some of which may require protection? You need a reliable forecast (especially if you may be away from home for a few days or more in the winter). What I try to do is (i) stick with short-range forecasts; (ii) stick to the most reliable/expert forecasters; and (iii) keep an eye on what the weather is doing in your own microclimate. You can see my own temperature monitor live on this site (on my webcam page).