It happened at approximately 6 p.m. at a home on Chandler Road in Cheltenham Township.
Authorities say the boy was attending a birthday party when the incident occurred.
According to police, the branch fell about 50 feet while a group of children was playing in a driveway.
He was rushed to the Children's Hospital of Philadelphia, where his arm was later amputated. The boy was listed in critical condition.
WATCH | 2-year-old injured after being trapped under fallen tree branch in Montgomery County
2-year-old injured after being trapped under fallen tree branch in Montgomery County
"It's scary. It's definitely scary," a mother in Wyndmoor told Action News.
This incident was not the only instance of tree branches snapping unexpectedly over the weekend.
Residents in Wyndmoor told Action News about three hours after the young boy was hurt, they heard a loud 'boom' on Campbell Lane.
A tree unexpectedly snapped in half, landing on wires and causing a huge explosion.
"I thought it was fireworks," recalled Marcie McGoldrick from Wyndmoor.
It also led to several power outages that impacted roughly 360 customers. PECO was able to restore power within a few hours.
Another Wyndmoor resident said a tree fell in her backyard during the week as well.
"I have dogs. Fortunately, they weren't out there and I have an 8-year-old son who is always out there playing his rebounder because it's summer and fortunately he wasn't out there," the woman told Action News.
Some believe the scorching weather is a contributing factor.
"It was kind of crazy. It's not something you expect when it's not a windy day. It's just completely still, hot, and dry," said McGoldrick. "I would like some rain. I think it's something we have to be aware of that I didn't think about before."
Police say the incident with the branch injuring the young boy appears to be a freak accident.
Authorities say they are investigating, however, and an arborist is expected to examine the tree on Monday.
Jack Morvin, a certified arborist, says the rising temperatures and lack of water may have been contributing factors.
"The trees are going to become weaker because they can't provide enough food to sustain themselves," said Morvin, Leo's Tree Care manager and certified arborist. "It could have had improper planting, improper pruning, add in a little bit of wind, but then having a problem not getting enough nutrients into the tree, it all kind of adds up to an issue."
He also said green growth doesn't determine the structural integrity.
"It's really important to get those trees inspected by a certified arborist. You want to do a risk assessment. You want to assess the base of the tree, you want to assess the lean and any targets there," Morvin said.
The fallen tree is set to be removed on Monday.
Investigators hope the arborist will determine why the branch fell and whether the recent heat and storms played a role.