The morning fog defied predictions it was likely to lift by 10 a.m., remaining dense even in Center City more than 40 minutes later.
Visibility, though, which was only a quarter-mile as of 8 a.m., had improved at half-mile at Philadelphia International Airport, which saw some morning delays. (To check a flight, go to www.phl.org.)
A bunch of rush-hour accidents - nine was the count around 8 a.m. - gave way to just a couple around the area nearly three hours later, according to traffic.com. (To check the roads, go to www.philly.com/philly/news/traffic.)
The fog should give way to a damp, warm day, with light rain and a little breeziness likely this afternoon and evening, according to the National Weather Service.
Some thunderstorm activity is possible this afternoon, according to AccuWeather.com.
The high could reach the mid 60s, which would challenge the record for several days this week, but not on this date, which hit 71 in 1966.
After tonight's low in the high 40s, the temperature range will shift downward, with highs around 50 under sunny skies through Friday, and lows near freezing in Philadelphia.
Rain could return Saturday night and Sunday.
For more on the forecast, go to http://weather.philly.com.