The arrival yesterday of "Kona weather" and the hazy vog that comes with it is a minor irritant for many, but a big pain for Tatiana Kobayashi.

"I know when it's here because the (vog's) smell gives me a headache," said Kobayashi, 48, who first experienced a negative reaction when she moved here five years ago from Greenwich, Conn. "It's very strong, like a chemical smell. It makes me nauseous."

All Kobayashi, who lives in the Manoa area, can do for relief is pop an aspirin.

"Vog" is haze from the Big Island's Kilauea volcano. Not only can it reach all the way to O'ahu, but it can bring discomfort for people with respiratory ailments.

A shift from trade winds to light south or southeasterly breezes produces the hot, humid conditions most Hawai'i residents find uncomfortable.

Lead forecaster Roy Matsuda of the National Weather Service said Kona weather is not uncommon at this time of year and current conditions will continue to Friday and possibly through the weekend, likely without yesterday's intermittent showers and overnight thunderstorm threat.

The state Health Department has 16 air-quality monitoring stations statewide, including nine on O'ahu, but vog contaminants are normally not at an alarming level, said Clean Air Branch manager Wilfred Nagamine.

"What you're seeing is a haze; it's not like Los Angeles smog," Nagamine said. "The volcano puts out sulfur dioxide and the wind carries it. What we get is a form of sulfates and particulates. It's usually nothing to be alarmed about and well below the state and national hazard levels."

The statewide air-quality monitoring stations are more an indicator for industrial pollution, Nagamine said.

City emergency services spokesman Bryan Cheplic said there were 15 calls for "difficulty breathing" from midnight to 3:30 p.m. yesterday. The daily average, he noted, is about 30 to 40 calls.

The vog and sweltering conditions — the afternoon humidity was up to 90 percent yesterday — sprinkled with showers wasn't ideal suntan weather but it didn't seem to bother visitors in Waikiki.

"Where we come from we don't tan, we rust," said Sheldon Murray of Vancouver, B.C., who is vacationing here with his wife, Jan, until Friday. "It looks like a heavy fog but it doesn't bother me."

Brianna Scars, 19, and her 21-year-old sister, Kristiana, of Seattle, spent a week in Hawai'i, got the tans they were seeking, and didn't mind one overcast day.

"Of course, you think of crystal-blue sky — which we get twice a year at home — and we got that here," Brianna Scars said.

Cal Halasz, 48, of Calgary, Alberta, closed out a five-day vacation yesterday and had never heard of vog before.

"It's new to me," Halasz said. "Does it have anything to do with what the North Koreans are doing? It was foggy, hazy and humid (yesterday) but it's not the end of the world. Where I come from, it's in the 50s. I'd rather have this."

Stephen Denyse of Chicago and his family didn't mind Kona weather at all two hours into their weeklong Hawai'i vacation. "We were here last October and it was like this. It's beautiful, better than being in the cold," Denyse said.

Former Hawai'i resident Mike Miller, 63, of Desten, Fla., pronounced it perfect weather for jogging along the banks of the Ala Wai Canal. "It's perfect and refreshing — what makes Hawai'i beautiful," Miller said.

Reach Rod Ohira at rohira@honoluluadvertiser.com.