HARMONY — The number of runners registered for the first Butler County Half Marathon is lagging — for now.

Dean Reinke, director of the nationwide USRA Half Marathon Series, of which this race is a part, expects more to sign up.

The 13.1-mile race is scheduled for April 17 and will begin and end at Seneca Valley High.

“The runners’ nature is to register within two or three weeks of the actual event,” Reinke said. “Weather is always a factor, the runners’ health. ... They want to know what they’re getting themselves into.

“We have a list of runners in every region and we’ve e-mailed thousands in that part of the country informing them of the race.”

The Butler County Half Marathon was planned as a warm-up race for the May 15 Pittsburgh Marathon, which is expecting a record numbers of participants.

Juan Bernal, a marketing director for the USRA series, said 106 runners are registered for the Butler County event, including 73 for the half marathon.

A 5K and a fun run also are part of the event.

“I’m anticipating us getting anywhere from 300 to 500 runners,” Bernal said. “The races have done well in this series so far this year.”

The Butler County Half Marathon will be the fifth of 28 scheduled races in the series, covering 18 states. The Lexington (Ky.) Half Marathon is slated for Saturday.

The Palm Coast Half Marathon in Florida had 400 runners Jan. 23. The Dade City (Fla.) event drew 150 runners Feb. 6 and the Columbia (S.C.) Half Marathon had 500 runners March 5.

Joella Baker, a member of the Rose E. Schneider YMCA board of directors in Cranberry Township who formed a running club there, designed the course for the Butler County event.

Reinke said his organization will oversee the event.

“The Pittsburgh Marathon is just going crazy and we’re hoping to capitalize on some of its popularity,” Reinke said.

Mike Amarello is the USRA’s New England race director and will time and handle the results of the Butler County event.

“I’ve probably done 800 races over the past 10 years,” Amarello said. “Most of these half marathons have been pleasant experiences for the runners because we do have such a veteran staff.”

Amarello said he’ll be out on the course at 3 a.m. April 17 setting up signs and tables for water stops.

“We’ll peruse the course the day before, familiarize ourselves with it, so we’ll know what we’re doing in the dark,” he said. “A lot of work goes into setting up a course that is both scenic and safe for the runners.”

While most of the runners will be from this region, Amarello said a select few will travel a long distance to compete.

“There are members of clubs out there who want to run a half marathon in every state. We’ll get a few of those,” he said.

Registration for the half marathon is $60, the 5K costs $25 and the Fun Run is $10.

Visit butlerhalf.com for information.