The tractors returned to Elland Road at 7am on Saturday morning following overnight snow in Leeds.
An early morning clean-up operation was underway in a bid to protect the club's proud record of beating the inclement weather.
The areas around the stadium were being cleared of snow while the pitch also had a covering.
Temperatures again fell to as low as minus six on Friday evening, but the undersoil heating was in operation.
United are due to take on league leaders QPR at Elland Road when a crowd of around 30,000 is expected.