Urban areas are particularly susceptible to the algae growth because of the variety of nutrients found on nearby roads, sidewalks and sewage pipes, as well as the relatively shallow lakes and ponds, which allow nutrients to mix more easily.

Though small blooms of the toxic algae have been consistently found in New York state lakes and ponds in recent years, scientists have said the intensity of recent rainfall, which has been linked to climate change, may be contributing to this year’s blooms.

“There is a relationship between a changing climate and increased intensity of storms,” said Marit Larson, the chief of natural resources in New York City’s Department of Parks and Recreation.

“Generally, in the last few years, we are seeing it occur in lakes around the city,” Ms. Larson added. “And because it’s something we know could become worse in the future, we are paying more attention to it.”

City park officials, for example, now sample suspicious algae growth for potential toxins at least every two weeks. The blooms will likely dissipate on their own when the chemical balance in the water is restored, officials said.