The schools, which were scheduled to reopen after summer vacation on June 18, would now open from June 21, said School and Mass Education Department Secretary PK Mohapatra.
Mohapatra said the decision was made in view of the prevailing heat wave condition across the state.
"If required, the vacation may be extended beyond June 21 also, keeping in view the weather condition," he said.
Hot and humid condition is prevailing in Odisha even after the onset of South-west monsoon on June 8.
The Regional Meteorological Centre, Bhubaneswar, has predicted that the monsoon will remain weak in Odisha till June 20.