Sunday's weather forecast continues to change as the 38th running of Wellstone's Dallas White Rock Marathon approaches. The staggering heat and high humidity predicted early in the week are no longer a threat.

According to the National Weather Service, the most likely scenario now calls for temperatures in the 50s through most of the race, with thundershowers likely. Temperatures are expected to drop throughout the day.

"I keep hearing different things," race director Marcus Grunewald said. "It depends on when the front comes through."

This is the first time in Grunewald's 10 years helping with the race that he's faced potentially adverse conditions.

"What it really comes down to is that conditions have to be safe," he said. "The Dallas Police Department has the final say."

He said runners will not have an objective view of the weather.

MIKE STONE / Special to DMN

Organizers hope this year's marathon isn't spoiled by foul weather.

"They don't think as logically as they would in other situations," he said. "They've been training eight months to do this race on this day."

Warm, humid conditions test runners' stamina. Early in the week, reports suggested temperatures could rise to 80 degrees with high humidity.

The latest reports suggest temperatures at the race start will be 56 degrees with 14-mph winds and 90 percent humidity. Temperatures are expected to fall a few degrees by noon and a few more by the time the course closes. The forecast calls for the humidity to remain high and for winds to gust up to 21 mph. Rain is likely throughout the race.