The weather may be getting warmer, but business seems likely to remain cold as New Haven’s summer events brace for potentially lackluster attendance.

Organizers of three major city events — the International Festival of Arts and Ideas in June, the Free Concerts on the Green in July, and the Pilot Pen Tennis tournament in August — have all expressed uncertainty over attendance and revenue for the next few months. And with the city’s budget, which includes funding for the events, yet to be finalized, event directors are taking extra precautions to ensure that the Elm City’s summer events continue to draw crowds.

Tourism in New Haven may fall short of last summer’s benchmarks, Town Green Special Services District Executive Director Rena Leddy said in an interview this week. Whereas the summer concerts on the Green, which have included performers such as Kenny Rogers and Boyz II Men in recent years, draw up to 90,000 people to downtown each July and August, in light of the economic downturn, travel and lodging expenses may deter some tourists from making the trip to the city, she said.

“While we have not seen significant changes over the spring, we have anecdotal evidence that there will be a downward trend with fewer people coming to downtown New Haven,” Leddy said.

As an early sign that the city will be experiencing a quiet summer this year, hotel occupancy rates have fallen by 2.7 percent last quarter, as compared to the same period last year, according to latest data from the Greater New Haven Convention and Visitor’s Bureau. Over the same time, shop vacancy rates have also risen at a faster pace than last year, according to estimates given by the Town Green Special Services District. And worse may be yet to come if city tourism projections for the new few months prove to be accurate, Leddy said.

The gloomy forecast for downtown mirrors the uncertainty that organizers of the International Festival of Arts and Ideas, an 18-day series of music and theater performances, and the Free Concerts on the Green say they feel about their events’ summer future prospects.

Anthony Lupinacci, the director of public relations for the Shubert Theater and the spokesman for the festival, said organizers are still awaiting the final outcome of Gov. M Jodi Rell’s budget proposal to replace earmarked arts grants with a more competitive lobbying system. While the proposed changes will not affect this year’s festival, Lupinacci said there remains concern over the future viability of the festival if the proposed changes go ahead.

New Haven’s Free Concerts on the Green, which derives funding from both the city and private sponsors, may also face a lower number of attendees this year as tourists cut back on travel or leisure expenses. While the free concert’s lineup for this year — which includes the New Haven Symphony Orchestra, the Squirrel Nut Zippers swing band and the gospel singer Oleta Adams, was finalized months ago — organizers cannot presage interest in the event, City Hall spokeswoman Jessica Mayorga said.

But Anne Worcester, director of the Pilot Pen tennis tournament, said she remains optimistic.

“We believe we will see an increase in attendance this year because we continue to make sure that Pilot Pen tennis is a fantastic value,” she explained. “We are providing an intimate atmosphere that lets fans get close to some of the best tennis players in the world.”

Worcester added that the tournament, a key lead-up event for professional players looking to enter the U.S. Open later in the month, aims to boost visitor figures this year by offering ground passes starting at $5 and special off-court events hosted by the tournament’s corporate sponsors. Nevertheless, she noted that visitors will be looking for value.

“We realize that in this economic climate, people will be scrutinizing how their money is spent,” she said.