Fair point, Margaret, I have never climbed Croagh Patrick, and I am sure that it can be nasty, like all mountains, which have their own weather systems.
But the rest of the route will not be over mountains. Challenged, I have googled what my general knowledge and instinct led me to assert before - see below. It's Galicia not Ireland which mentioned snow in ther general summary - I had to dig further for a suggestion of snow in Ireland!
I suppose it's because Ireland (and Britain) are surrounded by the sea that we have such a milder climate than other places at the same latitude.
The point I also wanted to make was that the comparison with Norway wasn't really fair. So now I am going to google the Norwegian climate!! ...
And I discover that the west coast of Norway has a temperate climate too and it isn't as cold as I thought! But inland is more 'continental' in climate terms!! Well, reading these, I still think I'd be prerpared to walk in Ireland (if not over Croagh Patrick) in March, but not do the St Olaf's Way until later in the year. (Actually, probably not then, because I'm a wimp and I heard a presentation about it and they could only carry 10 teabags (weight again) and I coldn't survive with only 10!)
NB I'm reading Josie Dew's book Long Cloud Ride about cycling in New Zealand in 2004 when there seems to be daily horizontal downpours (that's when there aren't cyclones) and cows floating away in rivers in spate! And I thought NZ was temperate too!
Climate of Galicia
The climate of Galicia is classified as Atlantic, with mild temperatures throughout the year. Although the wettest spots in the Peninsula are probably in Navarra, this is rainiest region of Spain, with well over 1,000mm a year across almost the entire region. The town of Vigo receives, for example, 1909mm. Most years, Galicia is swept by rainy fronts coming in from the Atlantic.
Snow falls inland abundantly during the winter, with Los Ancares being one of the snowiest areas in Spain. Maximum summer temperatures are around 20ºC.
http://www.iberianature.com/material/wi ... nature.htm
Climate of Ireland
The dominant influence on Ireland's climate is the Atlantic Ocean. Consequently, Ireland does not suffer from the extremes of temperature experienced by many other countries at similar latitude.
Average annual temperature is about 9 °C. In the middle and east of the country temperatures tend to be somewhat more extreme than in other parts of the country. For example, summer mean daily maximum is about 19 °C and winter mean daily minimum is about 2.5 °C in these areas.
Mean annual windspeed varies between about 4 m/sec in the east midlands and 7 m/sec in the northwest. Strong winds tend to be more frequent in winter than in summer. Sunshine duration is highest in the southeast of the country. Average rainfall varies between about 800 and 2,800mm.
With southwesterly winds from the Atlantic dominating, rainfall figures are highest in the northwest, west and southwest of the country, especially over the higher ground. Rainfall accumulation tends to be highest in winter and lowest in early summer.
http://www.met.ie/climate/climate-of-ireland.asp
Most of the eastern half of the country has between 750 and 1000 millimetres (mm) of rainfall in the year. Rainfall in the west generally averages between 1000 and 1250 mm. In many mountainous districts rainfall exceeds 2000mm per year. The wettest months, in almost all areas are December and January. April is the driest month generally across the country. However, in many southern parts, June is the driest.
Hail and snow contribute relatively little to the precipitation measured.
http://www.met.ie/climate/rainfall.asp
Norway's weather is warmer than might be expected from its geographical location. Due to the warmth of the Gulf Stream, most of Norway falls within temperate climate.
In Norway, the climate varies considerably from coastal to inland areas. The coastal regions have a climate with relatively mild winters and cooler summer months. Inland areas have a continental climate with colder winters, but warmer summertime (for example Oslo).
The Scandinavian country Norway has a climate that easily fluctuates from year to year, especially in its most northern parts. Those are located at the edge of the global temperate zone.
An interesting phenomenon in Norway (and some other parts of Scandinavia) is the seasonal change in the length of day and night. In midwinter, daylight lasts 5-6 hours in southern Norway and in the north, darkness prevails. Those dark days and nights are a Scandinavian phenomenon called the Polar Nights.
In midsummer, daylight takes over and there is no night darkness during June and July, even as far south as Trondheim. The name for this is the Midnight Sun.
http://goscandinavia.about.com/od/norwa ... norway.htm