With the New England winter drawing to a close – and not a single nor’easter in sight – Boston real estate agents and brokers say the clear skies seem to be resulting in early sightings of what had been a rara avis around these parts: Active condo buyers.

A combination of rising rents, better economic news and blessed weather seems to have buyers coming out in droves, with attendance at open houses way up and multiple offers on quality properties the order of the day.

But the increased buzz, while welcome in the short-term, could have long-term negative effects on pricing.

“I do think there’s significant evidence of an increase in activity coming off the sidelines,” said Kevin Ahern, co-broker/owner of Otis and Ahern in Boston. “Many more people out on appointments, quicker decision making for sure, and the inventory is dropping rapidly.”

Those thoughts were seconded by Alex Coon, Boston area manager for Redfin.

“What we’re seeing right now with condos is just crazy multiple bids,” Coon told Banker & Tradesman, saying he was aware of one condo in Somerville with no less than four different offers on the table as he spoke – from Redfin’s clients alone. “It’s a bit of a feeding frenzy.”

Coon said a booming rental market was helping to drive qualified buyers off the sidelines in hopes of a finding a better deal through purchasing instead of renting.

But that increased buyer interest has so far produced little in the way of closed sales – or new listings. According to data obtained from The Warren Group, publisher of Banker & Tradesman, year-over-year condo sales in Boston as a whole – including outlying neighborhoods like Dorchester, South Boston, Roxbury, Allston-Brighton, Jamaica Plain and Hyde Park – were down 5.5 percent in January, the latest month for which data is available.

But if pending sales are any indication – and much can happen between the offer and the agreement – February looks to be a banner month for condos. Pending condo sales statewide last month rose 35.3 percent year-over-year, according to the Massachusetts Association of Realtors. And many sub-markets in and around the city have less than three months of supply according to Redfin’s calculations, and Ahearn repeated similar numbers.

Ahearn said 2012’s early returns were probably limited.

“[Increased interest is] probably not going to show up in terms of closings until we get into another 30 days,” Ahearn said.

Upward Pressure

But while closed sales may still be in winter hibernation citywide, condo prices are already perking up. Year-over-year condo prices statewide inched up 1 percent in January to $247,500 from $245,000 in January 2011.

In Boston, the median price of condos began to creep up in January after ticking down at the end of last year, with January 2012’s median price of $384,300 a 3.9 percent increase over January 2011’s $347,000.

Median condo prices for the city as a whole had declined 2.6 and 3.7 percent in December and November, year-over-year, respectively.

And the combination of low inventory and increased interest is already exerting more upward pressure on prices as we enter the spring market, according to Boston-based buyer’s agent John Keith.

“Prices have definitely gone up – which is wonderful if you’re a seller,” he said. “But it’s not good for people who are thinking, ‘okay, we’re going to wait for this market to come down and we’ll finally be able to buy something.’ They’ll be stuck with sticker shock – maybe not as bad as it used to be, but there’s not going to be many good deals in this city.”

Ahearn concurred, saying that while the high-end market was steady, listings at or below $500,000 – normally 55 percent of the downtown market – were particularly slow.

And Ahearn said he sees little relief on the horizon.

“The pipeline is zero – without new developments coming out until Hayward Place and whatever follows after it, it will mean that we will have an incredibly tight inventory [for the next several years],” he said. “So in reality, what is probably going to result is that your transaction activity isn’t going to be that high because of a lack of inventory going forward. But your prices are going to go up because of a low supply.”

And that’s the part that worries Keith.

“If we don’t see that jump in inventory then we’re not going to see that bump in sales,” he said.