During winter months or when frost is in the ground mudjacking should never be completed. The frost causes the concrete to move and fluctuation in height. Also when frost is in the ground the concrete sticks to the soil and if too much pressure is applied during the mudjacking process the slab will crack. If the concrete is heaved when the mudjacking process is completed, the concrete will not go back to its orginal position when the frost is out of the ground. If this happens the slab or slabs will need to be replace. It is always best to wait until all frost is out of the ground before you have any mudjacking work completed.