If you regularly workout outdoors, skip it today. With so many dust particles suspended in the air, you may breathe in a larger amount of harmful pollutants. Further, while exercising, you are more likely to breathe through your mouth rather than your nose. This can cause health problems as the mouth is unable to filter out certain large pollutants in the air, unlike the nose.
Vigorous exercise should be avoided in such circumstances, especially if you have asthma, diabetes or any other breathing-related condition.