It's become so common, perhaps you've stopped noticing how often your local weather forecast is "above normal." It's noted during extreme heat in the summer, when mild temperatures persist through the winter, or when nights don't cool down like they used to.

But on May 4, the hotter Earth will officially become the new normal.

That's when the National Oceanic and Atmospheric Administration (NOAA) releases its once-a-decade update to "climate normals." They are the 30-year averages for temperature and precipitation that local meteorologists rely on as the baseline for their forecasts. To be sure, some updates will be minuscule. But the fastest-warming places will see a real bump in their averages that could make some forecasts seem confusing and pose a challenge to meteorologists.

The current "normals" are from 1981-2010, based on data collected by thousands of monitoring stations around the country operated by the National Weather Service. The NOAA update will shift the time frame for those averages later, to the period from 1991 to 2020. The decade from 2011-2020 is one of the hottest on record in the U.S.

"It was a very substantial upward trend in temperature, especially along the West Coast, in the South and along the East Coast," says Mike Palecki, with NOAA's National Centers for Environmental Information.

There were exceptions; some places in the North Central part of the U.S. actually cooled a bit. But globally, the decade ending in 2020 was the hottest decade recorded since 1880.

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After the NOAA update in May, with the baseline for normal shifting to higher temperatures, forecasters in Phoenix and many other places might not be pointing out as many "above normal" days as before. In fact, some days considered warm now may become officially "cooler" when compared to the new temperature average. Sullins plans to take more time in her daily forecasts to explain the shift.

"We're going to have to remind people, especially this year, 'Hey, if we're at 115, that is 5 degrees above the average. But remember that this average has changed," she says.

That context is important. Research shows that as unusual weather events happen more frequently, people simply reset their perception of what's normal. One study found a common reference point for "normal conditions" was only two to eight years ago.

Frances Moore, a co-author of the study and professor of environmental policy at the University of California, Davis, has seen this speed of "normalization" in her own state. After five years of extreme smoke events from wildfires, she says people now simply say, "Oh, fire season's coming, I guess we'd better get ready for it."