The spread of wildfires over the past two weeks has only continued to push smoke out across the United States.
The wildfires have burned swaths of California, Arizona, Washington and Colorado, and have sparked up in other Western states.
At the center of the wildfires, California Gov. Gavin Newsom issued a state of emergency. More than 100,000 people were asked to evacuate, some of whom were allowed to return to their homes this week.
In the fires burning in San Mateo and Santa Cruz counties, more than 20,000 people were ordered to evacuate. Those in the Bay Area were advised to stay inside their homes due to the far-reaching smoke.
See before and after photos of the smoke in the California wildfires:
source: nbcnews.com