The Fort McMurray fire—the one you probably forgot about—is still burning. In addition to the city it consumed to earn its name, the fire has burned forest over 500,000 hectares of land across northern Alberta. Which is roughly equal to: three and a quarter Oahus; one point six Rhode Islands; or all of Long Island plus Manhattan, Staten Island, the Bronx, Yonkers, Newark, Hoboken, Jersey City, Elizabeth, Fort Lee, Monache, you get the picture. This is—has been—a very big fire.

The question at this point is whether it will remain so. So far, wind and heat have made the burn nearly impossible to contain. But this weekend's forecast calls for rain and cooler temperatures. "We can fight as long and hard as we want, but the only thing that will stop a wildfire this size is rain," says aptly named Travis Fairweather, wildfire information officer with the government of Alberta.

Let's recap. Fort McMurray is—was—a city of some 80,000 people in the heart of Canada's oil country. The fire broke out on May 1, in the woods southwest of town. It jumped to a trailer park the same day, and by May 3 had consumed a quarter of the city. Officials declared a total evacuation. May is a strange time for a wildfire in the Canadian taiga forest. But this has been an El Niño year, and the winter brought little snow. That, combined with unseasonably hot weather, low humidity, and high winds, turned the fire into an inferno.

The still-burning fire stretches 370 miles long—as of yesterday it breached Saskatchewan. Over 1,000 forest fire fighters from nearly every Canadian province are working to hold that line. They have 50 helicopters, and 170 pieces of heavy equipment. They have dug containment barriers along a mere 38 miles of that total. These guard lines are about the width of a two-lane highway of cleared vegetation. "That is good for a fire that is calm and creeping, but if it is burning hot and heavy the guard lines won’t be able to stop it," says Fairweather.

Weather is the key. Northern Canada needs to get cooler and wetter. “A ten degree drop in temperature is the difference between moisture on the ground being evaporated or staying a little damp,” says Fairweather.

So far, it has not been a friend. "Shifting winds drew the fire north, towards some of the oil sands projects," says Shayne Mintz, the director for Canada's National Fire Protection Association. None of that has led to an outright petroleum inferno—the tar sands themselves are underground, and mining camps are required to clear huge perimeters of forest around themselves. Even still, smoky, ashy air forced 4,000 workers to evacuate from mining camps early last week.

At one point, the fire was so nasty it was even creating its own weather. “The plume of smoke above the fire had lightning coming out of it, and that lightning was hitting the ground and starting new fires,” says Fairweather. “I had never seen that before.” Yeah man, I’m pretty certain nobody has seen stuff like that since John the Apostle was fever dreaming up the Book of Revelation.

Right now, officials are optimistic. Last week, Fort McMurray officials announced they were hoping to start letting people back into the city starting June 1. But for most people, that first trip back will probably just be for reconnaissance. “We expect that ultimately people will go home for a brief visit to see their property, reclaim the things they wish they had, and continue to wait for a better, more proficient time for re-entry,” Melissa Blake, Fort McMurray’s mayor, said at the conference. The fire might go out, but it will take a while for the smoke to clear.