Strong thunderstorms caused flooding and knocked out power Tuesday as they moved across New Hampshire.The Merrimack Public Library in Merrimack was closed because of flooding. Staff members said the flooding began when heavy rain started falling about noon. The water leaked in through basement windows and soaked the carpet. >> Download the FREE WMUR appLibrary officials said they are waiting for a professional crew to come in to finish drying up and sanitizing the flooded parts of the building. They said they expect the library to be open Wednesday. This is the third summer in a row the library’s children's area downstairs has seen water damage. “We do have issues when it rains really hard, really fast, like it did today, with a gully right outside of our windows that doesn't drain quickly enough,” said library director Yvette Couser.The basement at Our Lady of Mercy Church in Merrimack also flooded. “When I opened the door here, I thought i had gone to Hampton Beach, because I walked into the water,” said groundskeeper Ron Ketchie. “This whole hall was just full of water.” Ketchie credits divine intervention for checking the basement: He only went downstairs to get his tools, otherwise, no one would have discovered the flooding until Wednesday. “The windows where these wells filled up – I guess it was pouring through two sections of the windows like Niagara Falls,” he said. “They were far out enough to fill the pews with water.”In Manchester, a Rite-Aid parking lot looked more like a lake, and many customers had trouble getting back to their vehicles. Along Elm Street, crews worked to clear drains along Elm Street where a large tree fell, ripping up the sidewalk. Another tree took out power lines on Carpenter Street, where many residents said they were dealing with flooding. "It's been terrible, because we've lost electricity, first of all, and that knocked out our sump pump," said Don Fournier, of Manchester. "So we have water flooding in the cellar with nowhere to go until the electricity comes back on so that the sump pump can move it out." Manchester Department of Public Works officials said crews went out early in areas that are prone to flooding ahead of the storm to try to prevent problems. Maple Street resident Josh Greenstein said Tuesday morning that he has had to deal with flooding before. "We put sandbags in the foundation and have done everything we can to prepare ourselves, and we're just waiting for the rain now," he said. Minutes later, the skies opened up over Manchester. Residents of four homes in the area said they have been plagued by flooding in recent years. They have begged the city for help, citing aging infrastructure that can't handle a sudden onslaught of water. "There's nothing you can do to stop it. Once it's coming in, it's coming in," Greenstein said. "So, the first time this happened in 2016, we all kind of freaked out. In the end, the fire department had to come pump out our houses." This time, DPW crews went to Maple Street early, armed with sandbags, a pump and road barricades. They also worked to make sure the storm drains were clear. "We are doing everything we can to try to minimize the water getting into the backyards, because they are lower than the street, so it's a natural gathering point for rainwater," DPW director Kevin Sheppard said. Maple Street flooded again, but a pump was already in place. Sheppard said the city may take the same strategy in the future. "We've got to start treating these rainstorms like snowstorms and start setting up for them," he said. Sheppard said 30 crew members were out all day working to alleviate flooding problems as they arose.“We are thrilled that they are now staying ahead of it,” Greenstein said. “Today is a unique situation – we had a six-hour notice on the flash floods.”