Four people working on a metal roof and a fifth person in the same area near the Calgary airport were injured by a lightning strike Wednesday afternoon, according to paramedics and firefighters.

Lightning struck a building at 580 Palmer Road N.E. around 2 p.m., said Carol Henke with the Calgary Fire Department.

Four workers were assessed on scene, and Henke said their injuries were not life-threatening, with three listed in "green" condition and one in more serious "yellow" condition.

In emergency response triage, the green designation refers to patients who are often described as "walking wounded" and may require medical care at some point, but not urgently.

The yellow designation is for patients who are more seriously hurt and require observation, but are not in immediate danger of death.

EMS spokesman Nate Pike said two of the workers, both men in their late 20s or early 30s, were taken to hospital in stable condition, while the other two did not require transport to hospital.

5th man assessed at another location

Pike said paramedics also responded to a second, nearby location in the 300 block of McTavish Road N.E., where another man also appeared to have been affected by the lightning strike.

That man was assessed and then transported to hospital in stable condition.

"Depending on the proximity to actual lightning strike, symptoms can vary significantly," Pike said.

"The biggest thing that we tend to worry about, first of all, is electrical interruption to the way the whole body works. Obviously, the heart runs on electricity and any sort of big blow of electricity can cause potential cardiac complications."

Funnel cloud warning issued earlier

Earlier in the day, Environment Canada issued a weather advisory for Calgary, saying the weak rotation of an approaching storm brought the risk of funnel clouds.

"This weak rotation is normally not a danger near the ground. However, there is a chance that this rotation could intensify and become a weak landspout tornado," the advisory stated.

"Landspout tornadoes do not usually cause significant damage but can still be dangerous. They can be strong enough to topple trees, damage roofs or toss debris short distances."