If you’ve just been to the islands, you most likely noticed the vog. Vog is what happens when the gases from an erupting volcano make friends with the sunlight, water vapor, dust particles and oxygen in the air. Let’s call it tropical smog, which is usually confined to the Big Island, and which doesn’t usually cause a ruckus; however, big time winds began blowing the sulfur gas and volcanic ash off Kiluea on April 8th, 2008, causing closures in and around Volcanoes National Park. Even nearby Maui was experiencing quite a bit of haze. The potency and severity of vog is measured by the vog index.
The park is open at the time of this posting, but you can always check the Parks Service for area closures before you go.

Post from: The Hawaii Traveler