Extended stay in February/March

There's a difference between having a warm, dry, comfy home to be inside during rainy, dreary weather, and being essentially homeless (or at least between temporary homes) on days like that. I think Ireland's weather is quite similar to what we get here in Seattle, so look outside and consider how you would do. Like here, the weather isn't always consistently miserable, the wet and cold comes and goes. But still, February (and to a lesser extent) March wouldn't be my top picks for getting outside and going hiking, either here or there. But it really just depends on 1) how tolerant you are of being out in the weather, and 2) how much freedom you have to pick your travel time of year. If all you can do is February/March or else you can't go, then take your chances. If you can go anytime...personally I like summers for that part of Europe. If you do decide to go, just plan on shorter days (winter) and plan to spend a greater portion of your time indoors. You could always get lucky and hit a long dry stretch (not super likely)...but bring the Goretex.

David's comments are on the money as usual.
The advantage of traveling in Feb/March is that you'll be there during their low season and will see lower prices for everything from accommodation to rental cars. I wouldn't worry too much about closures - the museums and pubs will be open and the main attraction in Ireland is the scenery anyway. And therein lies the rub. You'll be faced with short days (sunset around 4:30 PM), cold temperatures (Dublin averages about 4 snowy days per year in Feb. for example) and of course the likelihood of wet weather. All that said, if you're ready for it and are dressed for the conditions you'll likely experience (yes ... lots of goretex) then being outside those months isn't all that bad unless you catch the odd day when the rain is coming in sideways and in sheets.
Haven't been there in February but we did spend several weeks one March hiking around the Beara peninsula and Kerry. Though we sometimes experienced all 4 seasons on a single 3 hour hike, we found that the rain didn't linger but rather alternated with sunny conditions most days. As long as we had our waterproof hiking boots we were fine, and I have to say that one of life's great pleasures is settling into a convivial Irish pub after a hard day's hike, sitting next to a warming peat fire and nursing a pint or two of Guinness.
You already have a leg up by living in the PNW so you know what to expect. I'd say go for it.

Do you have specific sights to see/things to do planned? Will weather and shorter daylight hours be a hindrance?

I have a hard time getting my head around the idea of spending a bunch of money to sit for 10+ hrs in a metal tube and when I get there its the same dreary grey wet I had when I got on the plane. Your outlook on things may be different.

If grey and wet is no deterrent, then go for it.

Thanks for the input so far. The dates are not flexible, basically we have a window of time that we will already be over there (Europe) and I need a non-Schengen country to be in till mid May, when I can return to the Schengen zone in mid May.
I would like to rent one place for the whole time, so we will have a place to be on days that are just too wet and cold. So am wondering where would be a good place. I am zeroing in on the Dingle Peninsula but are there other suggestions?
My ideal is a place that has a town close enough to do grocery shopping every day or two, a nice area to walk near or right outside our house, and I require good internet so it can't be too remote. As well as having enough day trip possibilities to keep us entertained for a month. We are not big hikers, are more interested in walks, castles, towns, pubs and music.

My 2 cents: For a place that's central for exploring both the Ring of Kerry and the Dingle peninsula consider the stretch between Castlemain and Glenbeigh. You'll be out in the countryside but still less than an hour's drive from Killarney, Dingle, the Skellig Ring, and some of the prettiest scenery in Ireland.
Another suggestion is to stay near the village of Kenmare, from which you'll have easy access to most of the ROK as well as the very pretty Beara peninsula just to the south.
If it were me I'd make it a point to find a place on, or with a view of, the water to be able to enjoy some of the dramatic shifts in the weather as winter storms roll thru. Several years ago we booked a place for 2 weeks along the Sky Road near the village of Clifden in Connemara ... our favorite part of Ireland. It's only about 15 minutes into the village, which is charming in its own right with ample shopping and several pubs, yet still a world away from civilization. It was mesmerizing to watch the progress of the storms as they moved up the loch just down the hill - while sitting near a blazing peat fire. The location is handy for exploring the scenic wonders of Connemara as well as being close enough to the ferry landings at Rossaveal and Cleggan for day trips out to either the Aran Islands or Inishbofin ... one of Ireland's better kept secrets.
There are a number of search engines that specialize in Irish cottages and self-catering vacation rentals, but we've had particular luck with https://www.shamrockcottages.co.uk/ and http://www.kerry-coastal-cottages.com/Properties/Menu.html for our own searches. You can also do a google search for others, some of which offer specialty accommodation (thatched cottages for example) as part of their menu.
We've found that most of the self-catering places we've booked have robust internet connectivity, good enough for our purposes anyway, so I doubt that will be an issue for you.

IMHO, you can’t go wrong with Ireland. You can always hang out in the pubs and pass the time with the locals!

Thank you for that information on your favorite places, including Connemara and Inishbofin. We are from Tennessee, USA, and are planning a trip for the month of March to see relatives and friends in Ireland and Wales. We are ignorant about the tourist sites; are there some you particularly enjoyed? We'll have some free days in between our visits, and hope to drive north from Barry, Wales to see a bit of the Yorkshire Dales and Edinburgh. We don't want to kiss any stones or do any major climbing/hiking, but we enjoy the seacoast and shorter walks, maybe to see castles and sea caves and fishing villages, etc. Any information you can pass along will be helpful. Our main obligatory stops are in n. Dublin (Swords), Skibbereen, Limerick and Thurles, Barry (Wales) and possibly a couple of days seeing cousins in St. Albans, Birmingham, and York. We hope to spend roughly half the time in Ireland and half starting in Holyhead, Wales (from the ferry), north to Edinburgh and Stirling, then south to York/Birmingham/St.Albans, then west through Oxford to Barry, Wales, then back to Holyhead/Dublin. We have a month (still not enough) so have some free days in between the above places. We're exploring the camper van possibility since we don't know the exact dates for the other visits.

Thank you for any help you can give! - the Millers

We just found out from Spaceships Rentals that with an American driver's license AND an international driver's permit, we can legally rent a camper van or motor home and take it from the UK/Ireland and back again on the ferries. This may be old news to others, but it was new info to us, so I'm passing it along. Thank you, friends, for taking the time to write all that information and advice! :) Here are links to the State Department (discussion of Driver's Permit and where to get one) and to AAA or AATA for anyone needing to get an International Driver's Permit. I will check with our insurance company on Robert's good advice, AND read "the fine print." There always seem to be hidden "gotchas" in any travel deals, as we first found out to our sorrow with a "cheap" Bahamas cruise+hotel in the 1990's! But we still need reminders from friends to be cautious!
https://travel.state.gov/content/travel/en/international-travel/before-you-go/driving-and-road-safety.html#ExternalPopup
https://autoclubsouth.aaa.com/?zip=38004&stateprov=tn&city=atoka&devicecd=PC
and http://aataidp.com/