Please note that this article was written in 2012. Here is a link for the National Park Service where you can get up to date information about any fires that might be burning in the Grand Canyon.
Where there is fire there is (generally) smoke! Fall is the traditional season for managed burns at the Grand Canyon because of the ideal weather conditions. At this time of year there is generally very little wind, yet it is beginning to cool dramatically and humidity levels are usually a little higher than normal. The announced burns are scheduled for the North Rim of the Canyon. Thus the headline, "Smoky Skies" because even if you are visiting the South Rim you will see the plumes of smoke ascending from the North Rim.
It is sad to me that the last two weeks of services at the North Rim will be spent with smoky skies and smoky conditions. Especially since this is the time when the trees are still showing their colors. If you are planning to visit the North Rim understand that viewing conditions may not be ideal. And if you see a plume of smoke arising from the trees near the Entrance Station or within the Park you don't need to report a fire.
Keep in mind if you are hiking in the inner canyon (a very popular activity at this time of year) you may experience some smoky skies and reduced visibility because the smoke will likely settle in the Canyon overnight. If you are visiting the South Rim you may note some haziness and reduced visibility as well. For more information and a direct view from the webcam of the Canyon from the South Rim click here.