December is the sixth month of a fiscal year that starts in July, and it's an annual custom for lawmakers to make some spending changes mid-year to respond to changing needs.
That work gets underway Monday at the Statehouse.
Finance and Management Commissioner Jim Reardon said earlier this month he expects lawmakers to be looking at about $13.5 million more in spending on top of a budget that exceeds $5 billion.
Some of the new spending is expected to go to address strains on the corrections system from growing numbers of pre-trial detainees in Vermont prisons.
Reardon told lawmakers gathered for a budget preview Nov. 20 that the Corrections Department had seen higher-than-expected growth in the numbers of detainees tying up beds in Vermont's in-state facilities, forcing more transfers of post-conviction prisoners to private prisons out of state.
Another source of upward pressure on spending has come from the Vermont Department of Mental Health, which is seeking an additional $780,000.
Since flooding from Tropical Storm Irene forced the closure of the Vermont State Hospital in Waterbury in 2011, many people in mental health crises who would have been taken there instead have gone to emergency rooms. They often spend days in emergency rooms awaiting longer-term placements at other Vermont hospitals, Reardon said.