The decision was made as a precautionary measure to safeguard the health and safety of students, Johor Education and Information Committee chairman Muhammad Naqib Md Ghazali said in a statement late on Wednesday.
The school closures affect all 1,198 schools and 617,258 students across Johor.
Johor state has seen some of the worst Air Pollutant Index (API) readings in recent days, with the Segamat area recording an API of 187 as of 10 a.m. on Thursday.
Unhealthy API levels were also recorded in 38 areas nationwide, including the capital, Kuala Lumpur.
Birgunj schools to be closed for three days due to extreme heat