Not only has last night's/this morning's rainfall snarled traffic and turned off the lights, it's also going to delay flights at San Francisco International Airport all day.

According to SFO duty manager Bob Rotiski, the airport has instituted a ground delay program to run from 9 a.m. through 9 p.m. tonight.

That's because, since SFO's runways are only 750 feet apart and run parallel to one another, in times of diminished visibility Federal Aviation Administration safety regulations requires the airport to institute these formalized delays.

Rotiski says that arrivals and departures today are facing at least 46-minute delays, but that that time could increase if the weather worsens (which it might, later this afternoon). As always, he says, travelers or people picking up arriving passengers should check flight times online or with their airlines before heading out to SFO.

Related: Expect More Rain, More Power Outages, And More Wrecks All Day Monday