Blue-green algae (cyanobacteria) are naturally occurring bacteria that live in lakes and waterways.
The presence of sufficient nutrients, warm temperatures, and high levels of sunlight, together with calm waters, provide optimal growing conditions for blue-green algae.
Excessive growth, called an algal bloom, generally occurs during summer and autumn, however blooms can happen at any time.
Cool, cloudy and windy weather can help reduce blue-green algae levels.