SANTA CLARA – The weather forecast today at 49ers headquarters calls for an 80 percent chance of rain with winds up to 15 mph.

But Jim Harbaugh doesn't need someone with a fancy meteorological degree to tell him that. The 49ers head coach stepped onto the balcony outside of his office Thursday morning, looked to the east, saw a red sky and knew what was coming.

"That means, red sky at night, sailor's delight; red sky in morning, sailor take warning," said Harbaugh, who isn't always willing to deliver good quotes but has been churning them out this week. "So I anticipate that we'll have some precipitation, some weather, and that will be a great thing for us."

Perhaps no NFL head coach has been happier to see rough weather on the horizon.

The 49ers have not practiced or played in bad weather all season, largely the result of a La Niña year in California, and Harbaugh is eager to practice in the rain before Sunday's NFC Championship Game, which also promises to be wet.

It began drizzling midway through the 49ers' practice Thursday, but the heavy rain was not expected to arrive until today.

The New York Giants, meanwhile, have practiced indoors this week, although they will have a chance to test the the conditions at Candlestick Park during a walk-through Saturday.

Asked which team the bad weather favors, 49ers offensive coordinator Greg Roman said it's a wash.

Roman said receivers probably will have the edge over defensive backs because they know where they're heading and the defenders have to react. Then again, running backs might not be able to make the same cuts they would on a dry field, so the advantage turns to the defense.

Defensive coordinator Vic Fangio said a sloppy field also might take a bite out of the pass rush. Both the 49ers and Giants have outstanding defensive lines and largely rely on those lines to pressure the opposing quarterback.

"You never quite know how it's going to turn out, and who it favors until you actually know the degree of the sloppiness that it is," Fangio said.

"To me, there's never an exact science or what you play in that. You just have to see exactly what the conditions are. Players have to make sure that their footing is the best it can be, have the right shoes on knowing that it's a little slippery and play accordingly."

Defensive end Justin Smith, who was a force of nature himself in Saturday's win over the Saints, downplayed the conditions.

"The field conditions, this and that – the tide – it really doesn't matter," Smith said. "They are going to run the ball, they are going to play- action, that's what they do. They're not going to change who they are and what they do at this time of the season."

New York defensive coordinator Perry Fewell also was reluctant to overthink the weather.

"You fight all year to get here," Fewell told New York-area reporters. "It can snow, it can hail, it can rain, it can do whatever it wants to do.

"We're going to be there. We're going to be ready to play."

KEY MATCHUP

• 49ers tight end Delanie Walker vs. Giants linebacker Michael Boley

When the teams met on Nov. 13, Boley was injured in the second half and Walker had a big day. He led the 49ers in receiving with six catches for 69 yards while fellow tight end Vernon Davis had three catches for 40 yards, including a 31-yard catch-and-run touchdown in the fourth quarter. The Giants are unlikely to leave Davis, who had 180 receiving yards and two touchdowns Saturday, in single coverage like the Saints did. And that could create opportunities for the 49ers' second tight end. The 49ers have been careful to note that the Giants' linebacking corps is healthier and playing better than it did in Week 10. But the 49ers still should be able to create mismatches with Boley and inside linebacker Chase Blackburn. Of course, that is contingent on Walker, who is recovering from a broken jaw, playing Sunday. He is likely to be listed as questionable.

© Copyright The Sacramento Bee. All rights reserved.

Read Matthew Barrows' archives and blogs at www.sacbee.com/sf49ers.

• Read more articles by Matthew Barrows