There are now growing fears that, with temperatures expected to remain below freezing across widespread areas of the country over the coming days, the weekend's fixture list could be badly affected by the elements.
Related ArticlesThe Daily Bung: Have the Fergie doubters lost their minds?Blackburn-Aston Villa postponedLower league clubs feel pinchMancini keen on Patrick VieiraUnited flops face axe for CityBoycott: Owen should turn to feng shuiCity's decision to postpone Wednesday's semi-final tie was announced on Tuesday afternoon after consultation with local authorities, Greater Manchester Police, the Football League and United.
The North West Ambulance Service had already declared the region a major incident area and the risks involved in staging a fixture in front of a sell-out 48,000 crowd were considered too great.
Manchester City's chief executive, Garry Cook, said: "What was paramount in our thinking was the safety of fans travelling to and from the game, especially in light of the sub-zero temperature forecast for Wednesday night.
"In the end, everyone who was part of the discussions was unanimous that it would have been too dangerous to play the game."
Similar safety issues led to Blackburn calling off Tuesday night's tie with Villa, which is due to be re-staged on Jan 14, subject to the Premier League granting Blackburn's request to move their home game against Fulham back 24 hours to Jan 17.
City's league fixture against Stoke and United's home clash with Hull City, both planned for Jan 26, will now be rescheduled.
With Manchester Airport closed for the majority of yesterday, the Bolton Wanderers squad were forced to travel to London by train last night ahead of the Premier League game with Arsenal at the Emirates tonight.
The difficult weather conditions are imposing a financial squeeze on clubs in the lower leagues, with several recent postponements beginning to affect cash flow.
League One outfit Walsall had lucrative home matches against Norwich City and Charlton Athletic postponed over the Christmas period, costing the club some £100,000 in ticket revenue.
Chief executive Roy Whalley said: "We haven't had a winter like this for a long time, and the precarious financial situation of many clubs is an open secret.
"At most clubs, the match income is the biggest form of cash coming into the club, so there's an obvious risk that a lack of home matches is going to affect the financial stability of a club.
"For clubs that have large debts, this winter is going to be very, very difficult."
Bill Bratt, chairman of League Two side Port Vale, said: "If the weather continues to be as bad as it is forecast, then a lot of clubs are going to struggle to pay wages."