Denbighshire County Council is reminding parents and carers it has been notified that national strike action by members of the National Education Union (NEU) is planned to take place on February 1 and February 14.
The council says this may impact on the operation of schools within the county and that additional days are planned on March 15 and 16.
It adds: "This is anticipated to result in a significant reduction in staffing levels within schools and will affect all areas of Wales.
"All schools are currently assessing whether they can remain open or partially open on these days and if not whether the sites will need to be closed to learners on these days.
"Schools will communicate directly with parents and carers regarding individual decisions and information.
"In addition, the National Association of Headteachers have notified Denbighshire that their members will commence action short of strike action as of February 1.
"Alternative arrangements may need to be put in place during these days should your school close or partially close."
* Llangollen county councillor Karen Edwards has been officially notified by the council that Ysgol Bryn Collen (Primary) will be closed on February 1 due to industrial action.