Why There Is A Change Coming To Your Local Weather Forecast

NOEL KING, HOST:

There is a change coming to your local weather forecast. Next month, the data that it's based on will be updated. That will make the warmer climate literally the new normal. Here's NPR's Jennifer Ludden.

JENNIFER LUDDEN, BYLINE: Weather forecasters work off a 30-year average, and it gets updated every decade. Right now, what's normal for temperature and precipitation is based on 1981 to 2010. That's why we've all gotten used to this.

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UNIDENTIFIED PERSON #1: Well, temperatures for your Friday will be running about 10 degrees warmer than normal.

UNIDENTIFIED PERSON #2: Well, we got about seven degrees above average yesterday.

UNIDENTIFIED PERSON #3: Into tomorrow, above normal temperatures.

LUDDEN: The past decade was one of the hottest on record. Mike Palecki of the National Oceanic and Atmospheric Administration says that will show up in the new averages called climate normals. They'll drop the '80s and wrap in the 2010s.

MIKE PALECKI: It was a very substantial upward trend in temperature, especially along the West Coast, the South and along the East Coast.

LUDDEN: He says there were exceptions.

PALECKI: Oh, you could go to Fargo, N.D. That would be a place where it's actually cooled a little bit, if that's your interest, especially in the springtime.

LUDDEN: But the fastest-warming places will see a real bump up in their averages. Amber Sullins is chief meteorologist at ABC15 in Phoenix, where she says last summer was incredibly hot.

AMBER SULLINS: We set a record of 53 days at 110 degrees or hotter. The previous record was 33 days, so it wasn't even close.

LUDDEN: What's more, she says, in the entire past decade, Phoenix did not set a single record for low temperature. Now, oddly, after the update in May, some really hot days or nights could become officially cooler than the new normal. Sullins plans to take more time to explain all this.

SULLINS: We're going to have to remind people, especially this year, hey, if we're at 115, that is five degrees above the average. But remember, this average has changed. This average is not what it used to be.

LUDDEN: That's important, says Bernadette Woods Placky, chief meteorologist with the nonprofit Climate Central. She says research shows people are really good at simply resetting what feels normal. And she sees danger in that.

BERNADETTE WOODS PLACKY: We're not aware of how much warming is happening on a regular basis. It's that slow grind that's eating away at the changing normal that doesn't give you the opportunity, sometimes, to sit back and look at what it used to be.

LUDDEN: Marshall Shepherd heads Atmospheric Sciences at the University of Georgia. He wonders if even using the term normal might be confusing. And he agrees that for most, the new weather averages will not impress.

MARSHALL SHEPHERD: One-degree warming doesn't sound like a lot to most people. In fact, many people say, oh, great, I could have cookouts in December more often.

LUDDEN: But that steady warming has a big impact, which he says meteorologists can help people understand. It helps fuel increasingly extreme weather, wildfires, floods, hurricanes. Shepherd says other impacts are more subtle, things like rising food prices, declining water supply, the spread of vector-borne disease.

SHEPHERD: It's about things happening right now that are affecting their kitchen table issues, their pocketbook, their livelihoods and their health.

LUDDEN: Industries feel this impact, too. And for them, the official 30-year weather average is losing its relevance. NOAA's Mike Palecki says businesses want more recent data that reflects the risks they face now. Energy companies need to predict extreme heat and cold. Or take construction.

PALECKI: They like to know, how many days does it rain during a certain period of time? So they have a certain number of rainy days that they build into their plans.

LUDDEN: So for the first time this year, NOAA will also put out 15-year averages to help keep pace with a climate normal that just keeps changing.

Jennifer Ludden, NPR News, Washington.

(SOUNDBITE OF YPPAH'S "SHOT INTO THE SUN") Transcript provided by NPR, Copyright NPR.