It would entirely depend upon where in Ireland you were. One major factor was water. If your monastery was in a coastal region or one accessible via a large enough river, you’d likely be at quite high risk of raids. If you were inland of the waterways, especially if further than a day’s march, you’d likely be at less risk.
Another major factor was which kingdom you were in. Different Kingdoms and their Kings had very varied relationships with the Northmen. Some were allies, some were enemies.
To provide further context... The first known large scale invasion of Ireland by Northmen was in 839ad, led by Thorgest. He specifically targeted the religious centre of Armagh. Sacrifices to Odin were supposedly made on the memorial to Saint Patrick, which offended the Gaelic Christian Irish natives. So it was certainly a Holy war, particularly in the earlier days of Viking invasion.
By 841ad, Thorgest had established a fort in what is now modern Dublin, declaring himself the first King of all foreigners in Ireland. The Northmen spread using the rivers, establishing further settlements in Waterford, Limerick, Cork and Wexford. But there were still many regions (petty Kingdoms) which they could not penetrate, where you would be reasonably safe from Northmen to run a monastery.
In 845ad, the Kings of two of these petty kingdoms, Munster and Tara, rose against Thorgest. They ultimately captured and killed him, by drowning him alive (weighted down with rocks and thrown in a lake). Despite this, the Northmen continued to rule Dublin and migrate into Ireland, from all over Scandinavia, Orkney, etc. Over time more and more Gaelic-Norse were born, the children of Irish women and Northmen.
Thorgest’s death left a power vacuum, leading to a civil war in 845ad between two main Northmen factors, which the Irish sources called a war between the black versus white foreigners (believed to be Danish versus Norwegian Northmen).
There were also several uprisings against the Northmen by the native Irish. One of the High Kings of Ireland (who, despite the title, was just another King of another petty kingdom) attempted to drive the Irish out and won several battles, but it was not enough. They also tried and failed to lay siege to Dublin six times in this period.
By 857, Imar (believed by some to be Ivar, the boneless) and Olaf emerged as the rulers of the two main Northmen factions in Ireland. They made peace, declaring themselves as Kings of Dublin and equals.
This helped the Northmen expand their raids within Ireland. They even allied with some factions of the native Irish to prevent other native Irish factions (such as the ambitious King of Tara) attempting to expand their power. This power sharing agreement worked well, and later (circa 870ad) led to the invasions of Alba (modern Scotland) by Olaf, and the invasion of England by Imar, who defeated East Anglia, Mercia and Northumbria. Both leaders then returned to Ireland.
Olaf eventually died in a later battle against the Pict Constantine I of Alba in 872ad, but little is known of Imar’s ultimate fate. The descendants of Imar and Olaf continued to cause trouble in Ireland until circa 12th century, the dynasty was referred to as the Ui Imair. They continued to fight with and against the native Irish, bearing children with Irish women, until the two people’s and cultures were heavily intertwined.
I am only an amateur historian, so I hope that a professional, or someone with more knowledge than I, can expand upon this answer and educate us further!
It's hard to quantify how dangerous the risk of being raided by vikings was because most annals are fragmentary and were compiled centuries after the actual events. But contemporary artistic counts certainly paint an apocalyptic picture:
A 9th century poem found in a manuscript in St Gallen:
Is acher in gáith in nocht
fu·fúasna fairggae findfholt;
ní·ágor réimm Mora Minn
dond láechraid lainn úa Lothlind
The wind is bitter tonight,
it tosses the sea's white hair;
I need not fear the coursing of the sea,
by the fierce warriors of Lothland (Scandinavia)
From a contemporary chronicle (that I unfortunately cannot source right now):
"If a hundred heads of hardened iron could grow on one neck, and if each head possessed a hundred sharp indestructible tongues of tempered metal, and if each tongue cried out incessantly with a hundred ineradicable loud voices, they would never be able to enumerate the griefs which the people of Ireland - men and women, laymen and priests, young and old - have suffered at the hands of these warlike, ruthless, pagans."
Some are even comical, as in this Triad collected by Kuno Meyer:
¶232] Trí as anso bís do accallaim .i. rí imma gabáil & Gall ina lúirig & athech do muin commairchi
Three people who are the most difficult to talk to: a king amongst his booty, a viking in his hauberk and a boor under patronage.
But realistically, although vikings added a new sense of danger to the Irish clergy, specifically because they were pagan, the apocalyptic language they use to describe the viking era severely downplays how unsafe Irish monasteries were before the arrival of the Scandinavians. You see, the Irish had a habit of raiding and burning monasteries in rival kingdoms themselves for centuries before the first viking raids; Irish kings preyed on ecclesiastical sites so frequently that Donnchadh Ó Corráin, one of the premier historians of early medieval Ireland, suggested that the Scandinavians got the idea to target monasteries and churches from the Irish themselves, visiting Ireland as traders or fishermen before they took to the longships!
One particularly humourous example comes from The Fragmentary Annals in 851 AD, when Máel Sechlainn, King of Tara, consults the King of Connacht, Cináed, on how to deal with the vikings of Dublin. To clarify which king of Connacht we are dealing with, the annalist gives us this description: "Cináed son of Conaing, king of Cianachta—and it was he who had burned the churches and the oratories of the saints (as we recounted before)". So one Irish king asks another for advice on how to deal with vikings because he himself had sacked so many monasteries, though this is revealed to be a ruse to have Cináed killed. Unfortunately, due to the predictably fragmentary nature of the Fragmentary Annals, we don't get the juicy details on how many churches and monasteries Cináed plundered.
The Chronicon Scotorum, another valuable resource on viking age Ireland (which seems to have actually been composed during the period in Connacht) shows us just how much Irish lords plundered ecclesiastical sites - through the entire period, the Irish raided more churches and monasteries than the vikings themselves!
823: Galinne of the Britons with all its dwelling-places and oratory was burned by Feidlimid son of Crimthann.
833: Members of the community of Cluain moccu Nóis were put to death and their church-lands burned to the very door of their church by Feidlimid king of Cashel. The community of Dairmag were treated likewise—to the very door of their church.
844: (this occurs in the same year that the same community is raided by vikings) Cennétigh plundered and burned Cluain moccu Nóis.
850: Cinaed son of Conaing (the same character from the Fragmentary Annals), king of Cianacht, rebelled against Mael Sechnaill with the support of the foreigners, and plundered from the Sinann to the sea, both churches and peoples, and he sacked the islands of Loch Gabor, and the oratory of Treoit, with two hundred and seventy people in it, was burned by him, and the oratory of Nuarrach with sixty people.
907: An expedition by the Cenél Eógain i.e. by Domnall son of Aed and by Niall son of Aed, and they burned Tlachtga.
I was going to continue to compile these by searching "plundered" rather than "burned" but the results were far too large for a reddit post. Also keep in mind that these are only recorded plunderings from a regional annal; raids on minor monastic communities by regional lords might not have even been recorded. In searching for these, I saw that some of the major monastic sites like Clonmacnoise were plundered several times in the same year by both Scandinavian and Irish armies.
Monks weren't even safe from each other:in 760 the monasteries of Birr and Clonmacnoise fought a pitched battle, while in 807 the communities of Cork and Clonfert clashed on the battlefield, ending in “an innumerable slaughter of the ecclesiastical men and superiors of Cork.” So in total, the vikings weren't great, but the early medieval period in Ireland just wasn't a great time to be a monk in general. Irish kings had already realized that churches and monasteries were a handy source of loot decades before longships ever appeared over the horizon - the vikings were just scarier to Christian clergy because they were pagan foreigners, not because they targeted ecclesiastical sites.