PITTSBURGH — The weather is becoming a worry for the Winter Classic.

Rain showers and temperatures in the low 50s are being forecast for the Capitals-Penguins outdoor game Saturday at Heinz Field, hardly the conditions the NHL wants for its midseason showcase featuring stars Sidney Crosby and Alex Ovechkin.

While temperatures above freezing aren’t ideal, NHL ice chief Dan Craig said they wouldn’t necessarily affect a 2Z\x-inch thick ice surface that is refrigerated to a very low temperature — 22 degrees. Only bright sunshine in conjunction with warming temperatures would soften the ice.

Rain is the major worry because it would be unsafe for the players even if it falls only lightly. A light rain could freeze almost immediately after hitting the ice, creating an uneven surface that quickly could become unplayable. A steadier rain is even worse because it might flood the surface.

AccuWeather, based in State College, is calling for showers with a high of 50 degrees on Saturday — 14 degrees above the normal Jan. 1 high of 36 in Pittsburgh. The National Weather Service’s forecast is nearly identical, except with a high of 52. The Weather Channel is predicting temperatures in the 40s and a chance of rain.

While the game is set to start at 1 p.m., it could be pushed back to later in the day — even to the evening — if improved conditions are expected.

The predicted warmup would follow a steady month of cold in Pittsburgh, where the daily high temperature in December has been above 29 degrees only four times.

“It’s something you’ve got to deal with,” Penguins captain Sidney Crosby said Monday. “It’s something that’s a possibility, but it’s not unusual for a game like that. I don’t think you’re going to hear any complaints. We’ll just cross our fingers and hope all the conditions are well. I think whatever happens, whatever the forecast is, whatever the weather is, we’re just happy to be in that game.”

Sunday’s forecast is more favorable, but the window gets smaller — the game must be played in the morning so NBC’s telecast does not compete against NFL games. The Steelers play in Cleveland at 1 p.m.

AccuWeather is predicting snow flurries with a high of 38 Sunday. The Weather Channel calls for a high of 37 with rain or snow showers.

Until now, the Winter Classic has been played in near ideal conditions. It was brisk and cold for last season’s game in Boston and the 2009 game in Chicago, and the Jan. 1, 2008, game in Buffalo between the Penguins and Sabres was played in a light snow that resulted in a snow-globe effect for spectators and television viewers.

Craig, the NHL operations facilities manager, said the ice maintenance process is more sophisticated than it was for the first Winter Classic. That means the ice can handle more extreme temperatures.

The Winter Classic rink has been finished on top of a platform above Heinz Field’s grass turf, and ice-making began Sunday. The ice was to be painted white Monday, and the rink markings and logos are to be painted today. The ice is expected to mature by Thursday, when any final adjustments are to be made.

The ice will first be used for a Capitals-Penguins alumni game featuring Mario Lemieux Friday morning. The Penguins and Capitals then will practice, although only the Pittsburgh practice is open to the public. Friday’s forecast is for milder conditions with clouds, some sun and a high of 48 degrees.

Saturday and Sunday are the only days the Winter Classic can be played because the stadium must be turned back over to the Steelers. The turf has to be replaced for the second time this season before any Steelers home playoff game.

If the Winter Classic is not played this weekend, the game would be rescheduled for later this season at Consol Energy Center.