Dallas (CNN) — Scattered thunderstorms brought some relief to beleaguered Texas firefighters Sunday, but the first part of the week ahead is shaping up to be the kind of scorcher that has state officials worried.

Critical fire weather is expected Monday and Tuesday as a low-pressure system propels the dryline eastward across the state, according to the Texas Forest Service. Temperatures will be in the 90s, relative humidity will be 10% or less in some areas and winds will gust up to 45 miles an hour. Forecasters say atmospheric instability can cause existing fires to become larger.

The Forest Service responded to 17 new fires on Saturday, but the blazes were slowed by storms that brought softball-sized hail and reports of tornadoes. However, rain accompanied by thunderstorms can be a mixed-blessing for firefighters, since lightening can ignite new fires.

The largest of these new fires is the Pipeline fire in Tyler and Hardin counties. Covering some 7,101 acres, it was caused by an oil well flare. National Park Service personnel were involved in the fight against the blaze and it is now 90% contained.

Wet weather over the past few days helped firefighters maintain control over many of the fires burning in the state, the Texas Forest Service said.

The PK Complex of fires burning west of Fort Worth is now 50% contained, assisted by significant rainfall, the Forest Service said. On Sunday, crews worked on constructing lines through the 126,734-acre fire. They also burned pockets of vegetation around the fire’s perimeter.

One man’s stand against Texas’ wildfires

The 159,308-acre Wildcat fire in Coke County, north of San Angelo, is 75% contained. On Sunday, crews were able to focus on patrol and mop-up operations, according to the Texas Forest Service.

West Texas averages nearly 15 inches of rain a year, according to David Hennig, a meteorologist in Midland. Over the past six months, just 0.13 of an inch of rain has been recorded in that part of the state.

While October through March is typically the dry season, that amount of rainfall is far below what it should be, Hennig said.

Texas burning “from border to border”

Two firefighters have died since the latest outbreaks began, with numerous others injured, state officials said.

Tired by fire, ranchers fight on. Photo extracted from CNN video.