In south Wales, about 14 separate fires were being tackled by crews on Sunday.
Mid and West Wales Fire Rescue and Service said crews were dealing with blazes at Rhandirmwyn and Ammanford in Carmarthenshire and Hay-on-Wye and Brecon in Powys on Sunday.
They have also attended fires in Gorseinon, Swansea, and Tenby, Pembrokeshire, as well as an incident involving smoke in Llanelli, Carmarthenshire.
Chris Bryant, MP for Rhondda and Ogmore, said a fire in Treherbert, Rhondda Cynon Taf, had been “appalling” and he thanked crews from London who had provided assistance.
“Thankfully, there are fire engines from all over the UK and two helicopters have been in place all afternoon.
“I’m immensely impressed by the fire workers. But this can’t be our new normal,” he said, in a post on X, external on Saturday.
Monahan praised the Royal Logistics Corps and Royal Engineers in ensuring crews had water to tackle the fires.
“The Welsh water system is under pressure, so they’re moving vast quantities of water from areas that we have it into areas where we’re fighting the fire, so that we don’t put too much pressure on the water system,” he said.
“That’s something people probably aren’t aware of.”
He also said the national emergency fire alert issued by the UK government to people’s mobile phones in England and Wales on Friday was “absolutely necessary”.
But he expressed disappointment that some people still did not appreciate the dangers.
“Even after that transmission, I stopped and found someone who was burning tyres underneath a tree.
“This is irresponsible behaviour,” he said.