It’s still early September, which is too early for the leaves to turn colors and fall in Northern California. In Sacramento, where I live, the leaves start shifting hues later in the month; some drop in October, but the piles of leaves that really signify autumn is in full swing don’t come about until November.

This year, however, with no rain in months and searing temperatures, many of the huge old trees of Midtown—some of which have been around since the 19th century, and which cement Sacramento’s reputation as a city of trees—have already shed most of their leaves. Those leaves, a dull, sickly, brittle brown, are piled high in the streets, awaiting a leaf-collection service whose schedulers still assume that November is when the season begins.

It’s really, really hot in California this week, with temperatures in Sacramento peaking at an eye-popping 116 degrees on Tuesday. For days on end, thermometers have climbed well north of 110 degrees, with triple-digit temperatures lasting late into the night.

This isn’t just the statistical vagaries of nature; this is accelerated warming due to climate change. All through the American West, abnormal temperatures abound: record temperatures as far north as Boise, Idaho, and Billings, Mont., in much of California, and in Salt Lake City.

Earlier this week, I drove east, from San Diego to Tucson and into New Mexico. On the first day of the drive, once we got a few miles inland, the temperature didn’t drop below 107 degrees until the early evening. For most of the drive, the car’s thermometer registered 113 degrees.

This sort of weather strains power grids beyond all reason, as residents crank up their air conditioners and turn on their TVs in lieu of going outside. By only the narrowest of margins did California avoid rolling blackouts on Tuesday. It also shows, beyond any reasonable doubt, just how quickly climate change’s most catastrophic effects are now barreling down on us.

Last week, scientists released a study showing that mega-floods—virtually biblical events triggered by a month of nonstop torrential rain that turns much of California’s Central Valley into an inland sea for months on end, and devastates the entire region’s agricultural base—used to occur only once every few hundred years. With climate change, the estimates are that in the next century they will start happening once every few decades. If (or when) the next one occurs, it could well be the world’s first trillion-dollar natural disaster.

Think that’s hyperbole? Look at what has happened in Pakistan this past month, with floodwaters swamping more than one-third of the country, thousands dead, and millions left homeless and without easy access to safe drinking water or food.

Heat waves and wildfires, followed by monsoons, do terrible things to infrastructure. Paradoxically, water systems are particularly at risk: Fires wipe out forests and degrade the integrity of the topsoil. When monsoons arrive, they then deposit huge amounts of charred debris into water systems. The carbon in this debris reacts with the chlorine used in water treatment processes, and the chemicals produced can be carcinogenic. Witness what has happened in the small town of Las Vegas, N.M., where 20,000 people are at risk of losing their entire water supply later this month after a series of fires and floods. The longer that cities, states, and countries wait to deal with this crisis, the more there’s a risk of catastrophic systems failure.

Last week, as the year’s legislative session drew to a close, California’s legislators passed a mammoth $54 billion in climate change investments, which were promptly signed by Governor Gavin Newsom. (Newsom also, at the 11th hour, signed the FAST Act, improving workplace conditions for fast-food workers, which I wrote about in last week’s column.) The centerpiece of the climate package is a commitment by California to entirely stop adding carbon dioxide into the atmosphere by 2045. There’s no doubt that this is massive, and bold, and in the long run will be instrumental in greening the American economy. But in the short term, it won’t stop the heat waves and the fires and the other aberrant weather that has already been unleashed by humanity’s sluggish response to the climate crisis, and which is becoming the norm in heavily populated states such as California, as well as in sparsely populated ones such as New Mexico.