A helicopter was brought in to tackle a mountain fire near an open-air swimming pool in Rhondda Cynon Taff on Saturday.
The blaze started shortly before 11:00 BST on Graig Mountain, and smoke could be seen by people enjoying the weather at Pontypridd lido.
Firefighters were also busy dealing with other grass fires at Abertillery, Blaencwm, Cilfynydd and another near Risca in south Wales.
In north Wales, crews tackled blazes at Gwynedd and Flintshire.
And Mid and West Wales Fire and Rescue Service said it dealt with grass fires in Llandeilo and Croeserw.
At Graig Mountain, a helicopter dropped water on the fire which covered about five hectares (12 acres) of the mountainside.
North Wales Fire and Rescue Service was dealing with grass fires at Bangor Mountain and Dorothea Quarry, near Caernarfon, with a third at Pentre Halkyn on Saturday evening.