In February, the United States did something that it had not done in many years — the country sent more electricity to Canada than it received from its northern neighbor. Then, in March, U.S. electricity exports to Canada climbed even more, reaching their highest level since at least 2010.

The increasing flow of power north is part of a worrying trend for North America: Demand for energy is growing robustly everywhere, but the supply of power — in Canada’s case from giant hydroelectric dams — and the ability to get the energy to where it’s needed are increasingly under strain.

Many energy experts say Canadian hydroelectric plants, which have had to reduce electricity production because of a recent drop in rain and snow, will eventually bounce back. But some industry executives are worried that climate change, which has already been linked to the explosive wildfires in Canada last year, could make it harder to predict when rain and snowfall will return to normal.

“We’ve all got to be humble in the face of more extreme weather,” said Chris O’Riley, president and chief executive of the British Columbia Hydro and Power Authority, which operates hydroelectric dams in western Canada. “We manage from year to year the ups and downs of water, and when we have the downs like we’re having, the lower levels, it’s common for us to import power, and we expect to continue that this year.”

The United States and Canada have long relied on each other because power use tends to peak north of the border during the winter when Canadians use electric heaters, and American electricity use peaks in the summer during air-conditioning season.

The abundance of Canada’s hydroelectric power has been a cornerstone of the trade, providing relatively low-cost renewable energy to California, Oregon, Washington State, New York State and New England.