Vog was affecting parts of Oahu today and may linger around the smaller islands until Tuesday, a National Weather Service forecaster said.

This morning, a haze hung over downtown Honolulu partially obscuring the mountains behind.

About noon, the air quality for Honolulu, Pearl City, Sand Island, and Kapolei was in the “moderate” category, according to the U.S. Environmental Protection Agency’s airnow.gov website.

Moderate means the air quality is acceptable, but there may be a moderate health concern for a small number of people who are unusually sensitive to air pollution, the website said.

National Weather Service forecaster Bob Burke said the vog would likely clear up on Tuesday with the return of the trade winds.

He said a front about 150 miles northwest of Kauai caused a shift in winds to a more southeasterly flow, which was carrying the vog from Kilauea Volcano on Hawaii island to the smaller islands. A high pressure area that normally brings the trade winds was too far away to bring much relief.

Burke said as the front approaches Kauai, the winds will shift to a more southerly direction, sending the vog north of the state.

On Tuesday, the front is expected to weaken, allowing the trade winds to return and stay through the rest of the week.

Kauai could see some locally heavy showers from the front as it approaches the state.