Planes have dropped fire retardant over the Texas Panhandle and a small community was ordered to evacuate as firefighters kept up efforts to stamp out the largest wildfire in state history while contending with new blazes.

Strong winds spread the flames further on Sunday, prompting an evacuation order to be issued in Sanford, a town of a little more than 100 residents, according to the Amarillo office of the National Weather Service.

A cluster of fires has burned more than 4900sqkm in rural areas surrounding Amarillo, including the largest blaze spilling into neighbouring Oklahoma.

As firefighters battle to contain the unprecedented wildfires, humanitarian organisations are pivoting their attention to victims who have lost their homes and livelihoods in the blazes.

Residents began clearing affected property on Saturday, and by Sunday the extent of the loss began mounting.

During an interview with CNN on Sunday, US Homeland Security Secretary Alejandro Mayorkas said the federal government has devoted funds, equipment and personnel to assist with battling the fires, but warned that more extreme weather could be coming.

“More than a million acres have burned. And we are in winter, and this is the largest fire in Texas history,” Mayorkas said.

“We, as a country and as a world, have to be ready for the increasing effects of extreme weather caused by climate change. It’s a remarkable phenomenon, and it will manifest itself in the days to come, and we have to prepare for it now.”

The National Weather Service issued red flag warnings – signifying extreme fire risk due to warm temperatures, low humidity and strong winds – across much of the central US on Sunday, including Texas and its neighbouring states of New Mexico and Oklahoma.

Red flag warnings also covered nearly all of Nebraska and Iowa, along with large swaths of Kansas, Missouri and South Dakota. Smaller portions of Colorado, Wyoming, Minnesota and Illinois were also under red flag warnings.