Tomato blight in June. A Schuylkill Expressway mudslide in August. Soggy costumes and a World Series game delay on Halloween.

It was already a wetter-than-normal year, thank you very much.

And then came December, which will go down as the wettest 12th month of the year on record.

Even before this morning's snowfall, Philadelphia officially had logged 8.58 inches of precipitation since Dec. 1, more than 5 inches above normal.

The year's total before this morning was a soaking 52.22 inches - fifth most on record, just 0.57 inches behind the next-highest total, in 1979.

"It is possible we could move into fourth place," said Gary Szatkowski, meteorologist in charge at the National Weather Service station in Mount Holly.

A key culprit is the tropical phenomenon known as El Niño - defined as a period of warmer-than-average water temperatures in the tropical Pacific. That leads to stronger jet streams across the southern United States, which draw in moisture from the Atlantic Ocean and the Gulf of Mexico that then can be deposited on the East Coast, he said.

"A big storm can grab moisture from hundreds of miles away across the Atlantic and bring it in over Philadelphia and produce rain or snow," Szatkowski said.

Brett Anderson, senior meteorologist with AccuWeather, agreed that El Niño bears part of the blame. It had been increasing since the fall and is now of "moderate" strength, he said.

A big chunk of this month's precipitation came with the 23.2-inch snowfall on Dec. 19 and 20. It added 1.75 inches to the precipitation total, as snow is measured in liquid form.

Then 1.8 inches of rain fell the day after Christmas, melting the thick white blanket in a hurry.

Dan Gattuso has a different way of measuring precipitation: by how much his phone rings.

He owns Dry Guys Basement Systems, a basement-waterproofing company in Woodstown, Salem County, that serves customers across South Jersey.

"It's obviously been a little hectic in the office, trying to field all the calls coming in," Gattuso said yesterday. "I'm not complaining."

His company normally is booked one week in advance; currently it is booked three weeks ahead, he said. Solutions include sump pumps, drainage channels, and systems that dehumidify and clean the air, he said.

The year didn't start out wet. The first three months of 2009 were drier than normal. Then April, May, and June were wet.

But serious moisture came in August - when the mudslide closed lanes on the Expressway and streets turned to streams at the oft-flooded Fort Washington Office Park - followed by an above-normal October. December's precipitation is more than double the average for the month.

Szatkowski, of the National Weather Service, said he doesn't see the region getting enough rain today to push the year's total past the all-time annual record: the 56.45 inches that fell in 1996.

Like plenty of others, he's OK with that.

"Frankly," he said, "we don't need any more rain."

Contact staff writer Tom Avril at 215-854-2430 or tavril@phillynews.com.