A sprawling storm system crossing the U.S. has overturned semitrucks on highways and fanned wildfires in Texas and Oklahoma. Tornado threats loom for the Mississippi Valley into the night and the Deep South on Saturday. The National Weather Service predicted extreme weather across a vast swath of the country that is home to more than 100 million people. Powerful winds gusting up to 80 mph were forecast from the Canadian border to Texas. A wildfire fueled by dry grasses and spread by strong winds prompted emergency officials to urge residents to evacuate the small town of Leedey, Oklahoma. Meanwhile the Oklahoma State Patrol said dusty winds toppled several tractor-trailers.

A new study finds that atmospheric rivers — the heavy rain and wind events most known for dousing California and other parts of the West — have been getting bigger, wetter and more frequent in the past 45 years as the world warms. This weeks' study shows that these long and relatively narrow bands of water vapor that take moisture from oceans and flow through the sky dumping rain in prodigious amounts have increased in the area they soak by 6 to 9% since 1980, increased in frequency by 2 to 6% and are slightly wetter than before.

Russia claimed Thursday that its troops have driven the Ukrainian army out of the biggest town in Russia’s Kursk border region, as a senior Kremlin official said that a U.S.-proposed 30-day ceasefire in the three-year war on Ukraine would help Kyiv by giving its military a break. The Russian Defense Ministry’s claim that it recaptured the town of Sudzha, hours after President Vladimir Putin visited his commanders in Kursk and wore military fatigues, could not be independently verified. Ukrainian officials made no immediate comment on the claim.

President Donald Trump says that he will double his planned tariffs on steel and aluminum from 25% to 50% for Canada, escalating a trade war with the United States’ northern neighbor. Trump says the increase of the tariffs set to take effect on Wednesday is a response to the price increases that the provincial government of Ontario put on electricity sold to the United States. Trump says on Truth Social that he will double the tariffs. The U.S. stock market promptly fell following the social media post.

A potent storm system is expected to pour heavy rain on western states later this week before rumbling into the central United States. Forecasters say it could spawn tornadoes in the South. The system could also dump heavy snow across parts of the Great Plains and Upper Midwest, creating blizzard conditions. As it moves east, a regional outbreak of severe thunderstorms is expected over large parts of several southern states beginning Friday and continuing into Saturday. That means a variety of severe weather hazards. A possible tornado touched down in central Florida early Monday, tearing past a local television news station as its meteorologists were live on the air.

Most of the 80,000 federal workers responsible for researching diseases, inspecting food and administering Medicare and Medicaid under the auspices of the Health and Human Services Department were emailed an offer to leave their job for as much as a $25,000 payment. The offer is part of President Donald Trump’s government cuts. The workers have until 5 p.m. on Friday to submit a response for the so-called voluntary separation offer. The email was sent to staff across the department, which includes the Centers for Disease Control and Prevention, the National Institutes of Health and the Food and Drug Administration.

Unless you choose to camp, overnight stays in national parks are likely to be quite costly d…