States are seeing these surpluses because early projections by their budget officers are proving to have been too conservative. An overall strong year for the stock market and a general economic uptick are generating more income, property and sales tax revenues than expected. At the same time, a milestone is about to be reached: In the coming months, budget officials expect that state revenues will climb back to their pre-recession level, even accounting for inflation.

The result: Optimism about digging out of the recession is occurring at the same moment surpluses are landing. But many experts in state finances say governors and legislatures may be too eager to spend the new money rather than paying down debt, bolstering shaky pension systems or setting aside money for the next downturn.

States got a taste of improved revenues last year, when estimates of how many investors would sell holdings by the end of 2012 to avoid new tax regulations proved too low — leading to a sharp rise in state revenues, 5.7 percent nationwide.

Fearing that this had been an isolated bump, most states again were very conservative in their revenue estimates for the current fiscal year. Now that actual revenues are being collected, the projections are turning out to be low.

“It seems that the bump was not just a one-time bump,” said Eileen Norcross, a senior research fellow at the Mercatus Center at George Mason University in Virginia, who specializes in state and local finances. “The rate of growth in 2014 for revenues was slower than in 2013, but still significant.”