The county council in Oxfordshire says estimated cuts of up to £200m are likely to be felt hardest next year.
The council needs to save up to £203m by 2015 after government spending cuts.
The county council's finance experts estimate the greatest proportion - about 50% - of the savings will need to be made in the 2011-12 financial year.
The council said it was already on course to save £35m this year from staff cuts, a pay freeze, management restructuring and cutting costs.
Council leader, Councillor Keith Mitchell, said care services were likely to be affected.
"It needs to be stressed that facilities in communities will close and valued services will be deeply affected.
"We still have big decisions to make on precisely where and how the cuts will impact, however there is no getting away from the fact that this is going to be tough for everyone.
"I would recommend that people prepare for these things to happen. This is particularly the case now that we believe a greater chunk of the cuts will hit Oxfordshire and local government as a whole from April next year."
'Heaviest cuts ever'
A council spokesperson added: "Finance experts at Oxfordshire County Council believe that a greater proportion than originally anticipated of the forthcoming cuts will have to be made in 2011/12 - leading to the likelihood of the heaviest cuts the council has ever had to make in any one financial year.
"However full detail will not be available until Local Government Settlement Day in December when individual councils discover in detail how much money they will receive from central government."
Last month, Chancellor George Osborne said in the government's Spending Review that local authority funding would be cut by 28.4% by 2015.
Afterwards, Mr Mitchell said it was "inevitable" the public sector was going to have to shrink.
In September, the county council announced more than 1,000 jobs could be lost.