Cat Bay - surf spot statistics

Best Surf Season (November - March)

The austral summer and early autumn deliver the most consistent window for quality surf at Cat Bay. During these months, the dominant synoptic pattern features a semi-permanent high-pressure system over the Great Australian Bight, which funnels a steady stream of southerly to southeasterly winds across the Bass Strait. These directions blow directly offshore at Cat Bay, grooming the swell into clean, orderly lines. Although the primary swell source remains the southwest quadrant – the result of deep low-pressure systems tracking south of Australia – the waves arrive with long periods (averaging 11-12 seconds) and average heights in the fun-sized to solid range (1.0-1.5m). The combination of offshore wind and workable SW swell, often wrapping around the west side of Phillip Island, produces peaky, rippable waves. Best results come when the high settles directly to the south, locking in light S winds and allowing longer-period SW energy to reach the beach with minimal chop.

Fair Surf Season (April & October)

The transitional months of April and October sit on the fence. In April, the subtropical ridge begins to shift north, weakening the reliable southerly flow. Ideal wind percentages drop to around 37%, and while the swell is still substantial from SW and WSW (with average heights around 1.5m and periods over 12s), the mix of onshore N and NNW winds increases, leading to more lumpy, bumpy conditions. October sees a similar pattern in reverse: the winter storm track is fading but still active, producing solid SW and WSW swells. However, winds are fickle – only 34% ideal. The occasional cold front passage can deliver a brief window of strong S winds and pumping WNW windswell, but these are short-lived. Both months require patience to find the cleanest sessions between frontal boundaries.

Low Surf Season (May - September)

The winter months from May through September represent the most challenging period for surfing at Cat Bay. A persistent stream of cold fronts and low-pressure systems across the Southern Ocean drives N and NNW winds across the Bass Strait, directly onshore at this north-facing beach. Ideal wind percentages plummet to between 17% and 28%, meaning the majority of the time the waves are blown out and choppy. Though the average swell height peaks at 1.6-1.7m and periods extend to 12.5-12.9s – offering plenty of raw power – the wind is almost always wrong. The dominant swell direction is still SW and WSW, but with onshore wind, the waves are messy and difficult to surf. Occasionally, a strong high-pressure system builds to the south, producing brief periods of clean S winds, but these windows are rare. If you’re willing to gamble, the few good sessions in winter can be exceptionally powerful and hollow, but expect to earn every wave.

September: Flickers of Spring

September signals the beginning of spring, and ideal wind improves slightly to 24%. The wind pattern becomes more mixed: N and NNW winds still dominate (combined 19.7%), but southerly winds (S 3.2%, SSW 5.6%, SSE 2.7%) begin to increase. The swell remains winter-like with average height 1.7m and period 12.9s – the longest of the year. Swell direction is still SW-heavy (45.1%) and WSW (21.0%), but there is a small but notable rise in NW (2.7%) and NNW (2.4%) swell. Wave heights in the 1-1.5m range (18.5%) and 1.5-2m range (14.7%) are strong. The longer period means the swell is extremely powerful. The key improvement is that southerly wind windows become more frequent and longer-lasting as the high pressure systems start their southward migration. Late September can offer some spectacular days with offshore winds and long-period SW groundswell. The season is just beginning to turn.