It's been a year of extreme weather.

Hurricanes have devastated Texas and the Caribbean, and monsoon floods have displaced millions and killed more than 1,000 people in South Asia. Meanwhile, one of the worst US wildfire seasons in years has ignited blazes across the west.

Almost 2 million acres of land — an area nearly the size of Rhode Island and Delaware combined — are currently aflame, according to the September 14 daily report by the National Interagency Fire Center. There are more than 100 active wildfires and at least 41 uncontained large blazes, battled by more than 25,000 responders, the National Guard, and half a battalion of active-duty soldiers.

Eagle Creek wildfire burns as golfers play at the Beacon Rock Golf Course in North Bonneville, Washington. REUTERS/Kristi McCluer TPX IMAGES OF THE DAY

"This one in particular has been a longer season. It really hasn't stopped since the fall of 2016," Chris Wilcox of the National Interagency Fire Center recently told NPR's Linda Wertheimer on Weekend Edition. "We had a long fire season in the Southern states — Georgia, Florida, et cetera — and now it's continued to progress and move and migrate its way westward as the seasons have changed through the year."

A staggering amount of land has burned so far this season — more than 8 million acres, along with more than 500 homes and other structures, according to the Fish and Wildlife Service (FWS). The Forest Service has spent more than $1.75 billion fighting fires so far this fiscal year, and the Interior Department has spent more than $391 million, the Los Angeles Times reported.

The La Tuna fire was the largest ever in LA and required evacuations from hundreds of homes. David McNew/Getty Images

And the fires keep coming. Normally by this time of year, the wildfire risk in the west has started to abate, Jessica Gardetto, spokeswoman for the National Interagency Fire Center, told the LA Times. "But we just haven't had that relief," she said.

Part of the reason this year's fires are so bad is the severe drought that hit Montana, Oregon, and other parts of the west over the summer. That significantly raised fire risk, according to FWS, and record heat waves dried out regions that had been soaked by snow and rain during the winter and spring.

Wildfires in parts of Canada have been particularly bad as well — British Columbia has had its worst wildfire season ever.

Research indicates that human-caused climate change has already had a significant increase on the overall number and size of fires. The amount of land burned in the US since 1984 was double what would have been expected without the effects of climate change in that period. And wildfire season has become about two and a half months longer since 1970 (a trend that's expected to continue).

Besides driving climate change, human activity plays a more direct role in fire season, too — 84% of wildfires are started by people, according to one recent study. A massive blaze in Oregon was allegedly started by teenagers who threw firecrackers into the dry forest. It covers 37,500 acres and is currently only 13% contained.

This Oregon wildfire has caused evacuations and sparked blazes across the Columbia River in Washington state. Tristan Fortsch/KATU-TV via AP

The fires raging in the western US have created plumes of smoke so big that they reach across the entire country, with potential negative health consequences for everyone exposed to the particles falling from the sky.

Healthy adults far from the flames don't necessarily have too much to worry about. But Dr. Gopal Allada, a pulmonologist at Oregon Health and Science University, told NPR that vulnerable groups like children, people over 65, pregnant women, and people with heart or lung conditions are at risk of serious harm from smoky air.

Until snow starts to fall on these western regions, they will likely continue to battle the flames.