StayING longer than 90 days in Europe without a Visa

Ireland isn’t in the Schengen zone, so time spent here isn’t included in your 90 day count. Ireland in November and December can be very wet and windy.

It's not the EU stay that you (necessarily) have to worry about. It's stays within the Schengen zone that exceed 90 days within any 180 day period that is the concern. Fortunately for you, Ireland isn't part of Schengen, so in the case you describe, you would be ok. However, if you wanted to extend your stay in Italy, or anywhere else in the Schengen zone, you would only be able to do that for another 30 days (very important to note that the clock includes your travel days into and out of the zone).

Yes, especially since Ireland is not a member of the Schengen zone. However, Italy and most of Europe is. Remember it is a limit of 90 out of any 180 day period. And leaving the zone does not reset the clock. It is a look back situation. If you look at your past 180 days and have you been in the zone for any 90 days total in that time period, you are done.

Britain is also not in the zone, so anytime you might spend there would also not count against the 90 day limit.

Wet and cold is something I'm expecting in the winter. I'm from California, so everywhere is wet, windy and cold to me:)
This may work well. If Ireland does not keep track of where I am in between, I will plan to stay 1 month in Ireland, then 80 days in Florence and another month in Ireland. That will be well over 90 days in Europe, but only 80 days in Schengen and 60 days in Ireland, which sounds like it will work. Thank you all!

If Ireland does not keep track of where I am in between

They will

Ok, Nigel. I guess that is my main concern. As long as the 90 day limit in Ireland is separate from the 90 day limit in Schengen, I'm safe. If Ireland looks at the additional time in Europe as part of their 90 day limit, that is the problem. So technically, I could stay 90 days in Schengen, then 90 days in Ireland and just keep doing that forever to avoid the limits? I have no intention of doing that, it's just a good way for me to see if I understand the requirements. By the way, I've had difficulty getting this articulated by the Embassy.

Don't over think it and don't make it complicated. Ireland is NOT part of the Schengen zone so time in Ireland does not count again the Schengen zone limitation of 90/180. And in the same light time in the Schengen zone does not count towards the Ireland limit of 90 days. If traveling between the two just make sure you have nice, clean entry and exit passport stamps and you know which pages are on in your passport. Might use a sticky note. You could do 90 in and 90 out assuming that Ireland doesn't any restrictions on the time periods. In the Schengen zone you are are looking back to see where you have been in the prior 180 days. That is the critical determination.

Thank you so much, Frank. I do indeed think I was overthinking it.

If you ever contemplate doing more than two 90-day cycles, you must be very careful, because both the entrance day and the exit day count. So Day 90 and Day 179 count against your time allowed in both the Schengen Zone and Ireland. On Day 180 you need to be somewhere else in non-Schengen land. Northern Ireland, Scotland and England are among the places that would work.

I'd caution against assuming that every time you turn up at the border of Ireland it will be a slam dunk and just walk back in. The reason I say that is you will be interviewed each time you arrive and it is up to the immigration officer each time to grant you entry. They can allow admission for some or all of the expected time. But they can also deny entry if they feel that your commuting actually constitutes residence, or for other reasons.

I believe that the UK limit is 180 days as opposed the 90 days for Ireland. Then you'd have to leave for 180 before the clock begins again. Keep in mind that you have free travel between the UK and Ireland with no border (as of now anyway pending Brexit) so Irish immigration authorities would have no idea if you move in and out such as from Northern Ireland.

Keep in mind that you have free travel between the UK and Ireland with no border (as of now anyway pending Brexit) so Irish immigration authorities would have no idea if you move in and out such as from Northern Ireland.

Not completly true. There is free travel between Northern Ireland and Ireland. There are no immigration checks when traveling from Ireland to Great Britain. However, traveling from Great Britain to Ireland, holders of U.S. passports must go through immigration in Ireland. (I have done this numerous times.) The free travel is only for British and Irish citizens.

Are you saying that there is an immigration check between Great Britain (such as Glasgow, Scotland) and Northern Ireland if I were to take a ferry across? My theory was that once in Northern Ireland, one could simply drive across the unenforced border into the Republic without notice. I can say that I flew from Dublin to Newquay, Cornwall last year and on that route we went through no immigration upon arriving at that small hole in the wall terminal, but as you noted above this was IRE to UK, not vice versa. It's all an academic point of course. :)

I would call current Immigration enforcement between the Republic of Ireland and the UK somewhat spotty and full of holes. Land crossing Ireland to Northern Ireland...no checks. Plane between ROI and England/Scotland; mixed. I have had to go through Irish immigration arriving in Dublin on Ryanair, but not on return to Leeds for example. Others reported not going through immigration on BA from London to Dublin though. Ferries, I have no idea. I think the statement that the Common Travel Area applies more to residents than tourists though is correct, each Country reserves the right to impose whatever limits on tourists they wish.