The council also cut the amount of waste it sent to landfill or Parc Adfer by 6,467.49 tonnes between 2024 and 2026.
Some bin collections were missed in Flintshire over the summer, partly because a heatwave became so serious that it posed a risk to the lives of workers, a council worker has said.
"Unfortunately, the heatwave was one of them and it was a contributing factor,"the worker said."There were some staffing issues during that period too.".
Drought was declared in all of Wales during the summer, and wildfires caused devastation in parts of the country.
At a meeting of the authority, councillors said the change to three-weekly bin collections meant the council should still hit its target despite the disruption.
They praised Flintshire residents for largely embracing three-weekly residual waste collections and for ensuring that the authority remained on target to hit its statutory recycling rate.
That improvement continued this year despite the problems that affected collections over the summer.