Grumari - surf spot statistics

Best Surf Season (May - August)

During the Southern Hemisphere winter, Grumari comes alive as a series of strong cold fronts and low-pressure systems track across the South Atlantic, firing long-period swell from the S and SSW quadrants directly into the beach's SSE-facing exposure. Average wave heights climb to 1.2-1.3m with periods consistently above 10 seconds, often reaching 11 seconds. The South Atlantic high-pressure system strengthens, promoting offshore winds from the N and NW quadrants a majority of the time. This combination produces clean, powerful surf that is both rippable and sometimes pumping. The highest percentage of ideal wind occurs in June (55%) and July (53%), making these the prime months for consistent sessions.

Fair Surf Season (March - April & September - October)

As the seasons transition, the swell window remains active but becomes more variable. March and April still enjoy robust S and SSE swell from late-season storms, with average heights around 1.0-1.2m and periods in the 10-second range. Wind patterns become less reliable, with increasing influence of the trade winds from the E and ENE, which can degrade conditions. September and October see a similar dynamic: the South Atlantic still generates sizable groundswell, but the frequency of ideal offshore winds drops to 37% and 31% respectively. This is a time of trade-offs—when the wind cooperates, the surf can be excellent, but those windows are narrower.

Low Surf Season (November - February)

The austral summer brings a lull in Southern Ocean storm activity. Average swell heights drop to 0.9-1.0m, and the dominant swell shifts eastwards with more ESE and SE energy that struggles to wrap effectively into the cove. Periods decrease to the 9-10 second range, resulting in less powerful waves. The trade wind regime dominates, with onshore E to ENE winds blowing 20-30% of the time, chopping up the surface. Offshore winds from the N and NW are less frequent, though they do occur. February stands out with a slightly higher ideal wind percentage (47%), but the smaller swell size limits quality. It's a time for smaller boards and patience.

October: Frustrating Onshore Winds

October is the most challenging month for consistent surf at Grumari. Average swell height drops to 1.1m, period to 10.1s, and ideal wind plummets to 31%—the lowest of the year. Swell direction is still decent: SSE (28.8%), S (27.7%), and SE (23.1%), but the wind is overwhelmingly onshore. The trade wind machine is in full force: E (15.1%), ENE (14.7%), and ESE (10.1%) dominate the wind rose. Offshore winds from N, NW, and NNW are scarce (total around 7% combined). This means the cove is often chopped up and messy, even when some south swell arrives. However, when a rare northerly land breeze coincides with a good S swell, conditions can turn magical for a few hours. It's a low-percentage game, but the rewards can be worthwhile for the persistent surfer.