Mayor Kirk Caldwell says 2019 was Oahu’s hottest year ever

By Nina Wu Feb. 20, 2020

Last year, Honolulu residents may remember hot, sweltering days, with numerous record high temperatures, as well a summer that seemed to last longer than usual.

It turns out that 2019 was Honolulu’s hottest year on record, according to the National Oceanic and Atmospheric Administration. It was the second hottest year on record for the planet Earth, and a year of record temperatures globally and locally.

Mayor Kirk Caldwell called the data evidence of a “climate crisis” during a news conference Wednesday at Magic Island, and said it was time for action.

“Weather is your mood today but climate is your personality over time, and our personalities are changing because of our climate crisis,” said Caldwell. “Here on the island of Oahu, the state of Hawaii and I think across our nation and the world, we’re seeing the impacts of our climate crisis in so many different ways.”

He noted the wildfires in Australia, and the record-high temperature of 64.9 degrees Fahrenheit recently set in Antarctica, as evidence. In Hawaii last year, the daily record high was set or tied 273 times, according to the National Weather Service. Of that total, 135 were new daily records.

Rising temperatures are no longer a projection for later this decade or later this century, Caldwell said, but are here now and a “crystal clear reminder” of challenges to be overcome.

The city on Wednesday also released results of an islandwide heat mapping survey conducted by Honolulu’s Office of Climate Change, Sustainability and Resiliency over the summer.

On Aug. 31, 2019, volunteers conducted a one-day “community heat assessment” to identify the hottest spots across Oahu. They traveled along local routes, equipped with sensors that automatically record temperature, humidity and GPS locations.

They found hot spots all across the island, from Waianae to Hawaii Kai.

The maximum heat index — a measure of what it feels like when relative humidity and air temperature are combined — was 107.3 degrees at the Waimalu Plaza Shopping Center in Aiea, as well as on the windward side, near the 7-11 store on Kalanianaole Highway in Waimanalo.

Hot spots were also found in Hawaii Kai, where the heat index was recorded at 106, and in Maili and Nanakuli, where the heat index was 105.

Coincidentally, Aug. 31 was also the hottest day of the year for Honolulu, with a temperature of 95 degrees Fahrenheit.

What to do about it?

Plant trees, according to Caldwell, noting his current initiative to plant 100,000 trees across Oahu by 2025. He noted that the heat index on Ala Moana Boulevard at Ala Moana Center was 105 that day but about 10 degrees lower at Magic Island, beneath the canopy of trees.

With information from the survey, city officials said they can determine where to plant more trees or to deploy other cooling strategies.

Data shows that there can be a range of as much as 27.7 degrees in the heat index from morning to afternoon as impervious surfaces such as concrete or asphalt heat up. Locations with more trees, however, experienced only up to 8 degree increases.

Caldwell said the city is also considering legislation to mandate greener buildings or adjusting setbacks from the seas. Trees, he said, should also be valued as infrastructure.

From a safety perspective, Jim Howe, director of the Honolulu Department of Emergency Services, said high heat can pose a health risk, including heat-related illnesses from youth at sports to kupuna.

Over the summer, first responders get a higher volume of calls for help from hikers on the Diamond Head trail, for instance, suffering from heat exhaustion.

Josh Stanbro, chief resilience officer, said the heat mapping serves as “a post card for the future of what the heat on this island is going to look like.” It will help the city anticipate how to defend residents from the emerging impacts of climate change.

Stanbro noted a record rainfall was also recorded over the summer, an anomaly.

“While we were breaking heat records, we were also breaking rain records, and that’s what global warming is really about,” he said. “It’s global weirding. It’s really pushing to the extremes, whether it’s heat, whether it’s rain, whether it’s cold snaps.”

Unfortunately, Stanbro said, looking ahead, the trend line for temperatures is going up, with more hot weather on the horizon.

“We just broke all the records last year,” he said. “By all indications, we’re looking at that as the new normal. That’s why we have to take action immediately to try to reverse that trend. We have to completely slam on the brakes in terms of burning carbon fuels for our energy source.”

Honolulu was one of 10 cities selected last year to partner with NOAA’s Climate Program Office, CAPA Strategies, LLC, the Science Museum of Virginia, and others to conduct the survey and create heat index maps. The preliminary community heat assessment report is available at


>> 107 — Aiea, Waimalu Plaza Shopping Center

>> 107 — Waimanalo, Near 7-11 on Kalanianaole Highway

>> 106 — Just west of Kalani High School

>> 106 — Hawaii Kai, Kealahou St. across from Sandy Beach

>> 105 — Ala Moana Boulevard at Ala Moana Center


>> 2019 was the hottest year ever recorded in Honolulu.

>> 2019 was the second hottest year on record for the planet.

>> 2019 was a year of record temperatures globally and locally.

>> In 2019, the NWS logged 273 record high temperatures and ties.

>> Aug. 31, 2019 was the hottest day of the year for Honolulu, at 95 degrees Fahrenheit.

Source: NOAA