No explicit definition of temporary was given so it will be fact dependent on the person's residency. The good news is there is plenty of history in other contexts (taxes, voting, driver's license, etc) that I think will apply here. IMHO absent some really weird circumstances I think it's going to come down to whether or not the person has, or is in the process of establishing residency.
Visiting family for three to four days isn't even close. As long as your dad doesn't do things like:
- Buy a house or sign a lease on an apartment
- Divest his interest in his current place of residence (e.g. sell his house in Texas)
- Try to register school aged children for school
- Convert his driver license to Ohio
- Take a job with a permanent, or at least indefinite assignment in Ohio
- Register to vote
... then he will be fine once this law becomes effective.
If the courts ever decide to set an absolute time limit I can't see it being anything less than six months because of the rule about carrying on a non-reciprocal out of state CHL after becoming an Ohio resident. Furthermore Ohio law allows a person to be in the state for 182 days a year and not be a resident for tax purposes. I suspect that any court confronted with the issue would look at those existing examples as a starting point.
Never ask if you can carry at a non-posted place, but always ask why you cannot at one that is!
Just because they offer call ahead seating doesn't mean you call ahead for carry permission.