Weather and Topography

Air quality is influenced not only by how much pollution is emitted into the air, but by meteorological and topographical factors as well. Weather and climate affect how air circulates, and the degree to which pollution builds up.

The Puget Sound region is a unique part of the country. No other region in the United States at this latitude has weather as moderate as ours, with mild temperatures and few serious storms. Our weather is largely a result of maritime influences and diverse topography. The jet stream typically supplies us with a steady supply of cool, fresh air off the ocean. This marine flow not only contributes to our mild climate, but also mixes our air – which helps keep pollution from building up.

We also sit in a bowl formed by mountain ranges to the east and west. Innumerable hills, valleys, and water courses add to the regions’ geographical diversity.

When we experience temperature inversions and the air becomes stagnant (little or no wind and warmer air aloft trapping cooler air at the surface), our basin and valley walls trap air pollution near the surface. Under these circumstances, air quality tends to decline and occasionally reaches unhealthy levels.