But as spring nears, the postcard landscape has largely turned into a muddy wasteland, with the boats of the local sailing club left stranded on its banks, as France's driest winter in 64 years kept the lake from filling up.
France, like most of Europe, is in the grip of a winter drought that is prompting growing concerns over water security across the continent.
For the month of February, the Ariege region, where Lake Montbel is located, has suffered from a rainfall shortage of 80%.
"We are only currently at ... about 25% of the maximum filling rate. At this time of year, we are usually closer to a 60% filling rate," said Xavier Rouja, who manages the lake's dam.
Lake Montbel is an artificial lake, which extends over 570 hectares and was created in 1985 by flooding what used to be a forested area.
The lake, roughly half-way between Toulouse and Perpignan, was initially created to irrigate the region's crops, but over time camp sites and hiking trails have sprouted around its banks, drawing thousands of tourists each year.
As he walks the lake's dried-up bed, sailing instructor Claude Carriere checks on sailing boats stranded a few meters from the water.
His club has had to cancel several competitions since January, as the lake's shrunken surface is no longer suited for sailing.
"We have a magnificent body of water when it's full. It's fabulous. It is a haven of peace, a place of leisure and relaxation," Carriere, who has been volunteering at the club since the early 2000s, told Reuters.
"When you see it like that, it's sad. It looks more like a muddy desert than anything. And that breaks our hearts in a way."
The club's management is already looking to diversify its activities to keep operating through future droughts.
Downstream, farmers are worried ahead of spring and summer.
"Lake Montbel, in fact, is the guarantee of income ... If tomorrow, we have to do without water, many, many of our farms will collapse and disappear," said head of the regional farmers' irrigation association, Christophe Mascarenc.
Mascarenc uses water from the nearby Ariege river and not from Montbel Lake. He nevertheless plans to cut corn production by 50% to 60% this year to save water.
Others in the region have turned to less water-intensive crops, such as sorghum, sunflower and even mandarins.
Authorities are also working on a plan to divert the nearby Touyre river to help fill up the lake, though the project has met opposition from environmental groups.
As the effects of global warming are set to intensify in coming decades, warmer and drier seasons will become more common, the head of the public Upstream Garonne River Interdepartmental Delegation, Franck Solacroup, said.
"The Montbel dam is representative of this (water) deficit situation and this level of filling, which is far from optimal at the start of the season," he said.
"In 2022, we really had conditions which will be the norm in 2050, due to climate change ... This is something we will have to get used to and therefore adapt to."