Dublin City Council has to "scramble" to find emergency places for homeless families any time there is a bank holiday, a homeless charity has said.
Anthony Flynn, from Inner City Helping Homeless (ICHH), said people put up in hotels or B&Bs often lose their places when the city is particularly busy.
This weekend is a bank holiday in the Republic of Ireland.
Dublin's Croke Park is also sold out for a GAA All-Ireland SFC quarter-final double header.
In May, several homeless families in Dublin were advised to stay overnight in Garda (Irish police) stations due to a lack of emergency accommodation.
Children in pyjamas
According to the Dublin Region Homeless Executive website, in May 794 families with 1,592 dependents were housed in hotels - and a further 305 families in homeless accommodation.
Mr Flynn of the ICHH said that on Wednesday night the charity dealt with a woman and her three children who had lost their place in a hotel.
"That family yesterday had been walking round town all day with three young children and sat in our offices last night with three children in their pyjamas," he said.
He said they were told they might have to stay in a Garda station as a last resort, but were finally put up in a hostel at about 22:30 local time.
Mr Flynn said he was told a number of other families had been in a similar position.
"It's the case that every time a bank holiday hits Dublin, rooms are being made unavailable to the council and the council are then scrambling to try and place people at night time," he said.
"We need to be planning better, the fact is hotel usage is not the solution in order to sort the homeless or the housing crisis.
"My fear is that tonight and tomorrow night things are going to get a hell of a lot worse as we move closer to the weekend and people are told they have to leave hotels because of this influx of tourists."
Eoin Ó Broin, Sinn Féin TD for Dublin, expressed concerns about homeless families ahead of this weekend.
"Every single night in the city is a crisis in the homeless services, absolutely every single night," he said.
"Croke Park is sold out on Saturday, so you're going to have 80,000 people. People will come on Friday or Saturday and stay a night or two. It's also a bank holiday weekend, there's a ton of tourists in the city.
"So I would be very worried that families who are in hotel accommodation are going to lose their beds over this weekend and you'll have an increased number of people going to the Focus Ireland intake team on top of the people who would already be presenting as homeless.
"It's going to be a real nightmare this weekend and that's before you get to all the single homeless people."
Emergency accommodation 'not the answer'
Focus Ireland works on behalf of the Dublin Region Homeless Executive to help families who are homeless to secure emergency accommodation.
It says homelessness will never be solved by providing more emergency accommodation.
"We know from the frontline work of our excellent services staff that one of the main reasons families are becoming homeless is that more property is being taken out of the rental market," said the group's Roughan MacNamara.
"This is happening because the landlord is selling up, or the house is being repossessed by a financial institution or vulture fund."
He added: "The government voted down legislation last year - the so-called Focus Ireland anti-homelessness amendment - which would have stopped the evictions of tenants in buy-to-let properties that are being sold or repossessed.
"We know from our analysis that if this legislation had been passed it would prevent up to 20 families a month from becoming homeless in Dublin alone."
Focus Ireland has called on the government to take action on this issue.
The ICHH's Anthony Flynn said he feared that the family who sought his help on Wednesday night would be in the same position on Thursday.
"They'll have to contact the council and basically they'll be told to wait until this evening again and they'll try and accommodate them at some level throughout the day.
"But if they don't find anything they'll land back down in our offices again," he said.
"When we're looking at three young children at 22:00 with nowhere to go to and being put into a hostel at 22:30, it's unacceptable.
"We need to build houses, we need an exit strategy for those people who are entering homelessness."