The National Weather Service has issued a relatively rare Code Orange weather alert for the Philadelphia area today. What that means is, written in the NWS’s preferred all-caps style:
AIR POLLUTION CONCENTRATIONS WITHIN THE REGION MAY BECOME UNHEALTHY FOR SENSITIVE GROUPS. SENSITIVE GROUPS INCLUDE CHILDREN… PEOPLE SUFFERING FROM ASTHMA… HEART DISEASE OR OTHER LUNG DISEASES… AND THE ELDERLY. THE EFFECTS OF AIR POLLUTION CAN BE MINIMIZED BY AVOIDING STRENUOUS ACTIVITY OR EXERCISE OUTDOORS.
In the summer, these occurrences are usually caused by hot weather. In the winter, when they are more rare, they’re caused by fine particulate matter. Just because a summer phenomenon is happening in the winter doesn’t necessarily mean global warming is to blame, however. According to the EPA, it’s still unclear how climate change is affecting the spread of particles in the air.
A lot of particulate matter is cleaned from the air by rainfall, so increases in precipitation could have a beneficial effect. At the same time, other climate-related changes in stagnant air episodes, wind patterns, emissions from vegetation and the chemistry of atmospheric pollutants will likely affect particulate matter levels.
via Code Orange Air Pollution Alert in Philadelphia Today | News | Philadelphia Magazine.