The race is expected to end with temperatures in the 40s after beginning with lows in the 30s.
"As we prepare for winter weather, the Chevron Marathon must go on," Houston Mayor John Whitmire said during a press conference Friday morning.
City and race officials stressed the importance of dressing in layers for both runners and spectators come Sunday morning.
"Make sure you protect your extremities," Houston Marathon Committee Medical Director Dr. Lars Thestrup said. "Layer, layer, layer."
Thestrup also urged runners not to shed clothing such as jackets and sweatshirts too early in the race.
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He said the wind would be a factor later during both the Chevron Houston Marathon and the Aramco Houston Half Marathon.
A few runners told ABC13 Friday afternoon that they aren't looking forward to the temperatures.
"I've never liked the cold," Kory Davison said. "Running a marathon in it makes it a little bit unfavorable."
That being said, many runners told Eyewitness News they love running in these conditions.
There will be warming buses and medics along the course.
Safety was another issue that came up during Friday morning's press conference, especially in light of this month's terror attack in New Orleans.
FBI Houston says there are no credible threats to the race at this time.
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