Ralph Freso / Getty Images It's become so common, perhaps you've stopped noticing how often your local weather forecast is "above normal." It's during extreme heat in the summer. It's when mild temperatures persist through the winter. It's 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 miniscule. 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.