True, but with exceptions! Algae can grow in virtually any environment that has carbon dioxide, sunlight, minerals and enough water – even very cold climates. The limiting factor in algae growth is often sunlight or minerals. When sunlight is limited, some kinds of algae can take in organic substances, like plant matter, as food.
Hot weather does offer algae opportunities. Warmer temperatures prevent water from mixing, allowing algae to grow thicker and faster. Warmer water is easier for small organisms to move through and allows algae to float to the surface faster. Algal blooms absorb sunlight, making water even warmer and promoting more blooms, in other words, it grows fast in warm sunlight!