What makes the sky hazy

Department of Environmental Protection. Officials recommend that people who are unusually sensitive should consider reducing exercise outdoors as some pollutants may be a moderate health concern for a small group.

Rhode Island received an air quality alert Tuesday due to heavy smoke from the Canadian wildfires. Schichtel, B. Husar, S. Falke, and W. Wilson, Haze trends over the United States, Wolff, G. Kelly and M. Ferman, On the sources of summertime haze in the eastern United States. Science , , A useful site for monitoring haze and other atmospheric aerosols on a daily basis is the "Smog Blog" of the U. Louis anywhere, really, east of the Rockies.

The most recent cold front passed days ago. Since then, the air has once again become warm and humid, and the wind languid.

The familiar blue of the sky has given way to a milky pall that masks distant views. Yes, it's just another hazy day of summer! Because haze so frequently accompanies sultry summer weather in the East, Midwest, and South, it often is dismissed as a fact of life.

Indeed, there is a natural component to haze, derived, in part, from the emissions of trees and other vegetation. But much of what we see as "haze" is, in fact, a form of diffuse air pollution and, as such, a cause for concern.

Although haze can affect many things, it is most noticeable for reducing air quality, especially visual range visibility and contrast. Sunrise and sunset colors lose luster in haze, while rainbows and haloes may disappear altogether Figure 1.

Depending on its density and lighting, haze can sufficiently obscure the sky so as to hide weather hazards. For example, low-level cloud formations associated with tornadoes and severe convective winds are sometimes shrouded by haze Figure 2. More significantly, haze can sufficiently impair visibility to pose a hazard to aviation. For example, haze may have been a factor in the fatal crash of a single-engine plane piloted by John F.

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In early July, the winds transported the dense smoke south and southeast; the leading edge of the smoke made it as far south as Iowa and northern Illinois. While most of the smoke is high above ground, some smoke reached the ground. Last week the smoke was so thick and widely spread that some could smell it, and triggered a poor air quality warning for southern Wisconsin.

Surface visibility was reduced to miles at some locations in North Dakota.