Think for most councils those days have largely gone.

If a Central Government department (for example Department for Work and Pensions) doesn't spend all of its budget allocation for whatever reason, the department isn't able to carry forward any underspend to the next financial year, and the underspend goes back to Treasury. Central government has a projected 13.6% spend reduction by 2014/15 compared to 2009/10 - with some departments projected to acheive large reductions (DWP 47.9%, DEFRA 27.5%, Transport 17.1%, Defence 15.2%).

As far as I'm aware councils have a different scenario. Councils are funded by a combination of central government grants, council tax, business rates and fees/charges from certain services (eg parking enforcement). Government grants have been managed downwards by central government, and council tax increases have been capped. So councils have been squeezed financially since 2010 and encouraged to make efficiencies each year. Approx one third of councils are expecting to dip into reserves to cope with tighter funding in 2015/16.

Obviously there will be some councils who manage their budgets better than others, so it could be possible that a minority will have a year end rush to spend allocation.

Or is it because the worst of the winter weather is behind us, and repairs, and new work are now being started in preparation for Spring, etc?

In central govt the move to 'accruals acounting' in nineties removed the worst inentives to year end prestigitation - stuff like pre funding utility bills . Nontheless I suspect there is still a need to burn savings and unused contingency before FY year end in some circs. Prhaps more so in local gov.

Money may also be reserved to specific heads of spend, hence building bike lanes rather than fixing pot holes. You might have underspent this yrs bike lane allocation (ie incentve funded from Wihtehall) due to reasons beyond local control. Next years is committed to high profile and deserving shemes but will be reduced if you underspend in 2014/15.