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.

December: Early Summer – Small and Windy

December ushers in the austral summer with small, inconsistent surf. Average swell height is 1.0m, period 9.7s, and ideal wind percentage rises slightly to 40%. Swell is dominated by SSE (32.2%), S (30.1%), and SE (19.8%)—decent directions but the energy lacks power and height. The trade winds are still strong: ENE (11.7%), E (11.3%), and NE (10.3%) blow steadily, though north winds (N 5.9%, NNE 8.7%) also appear with some frequency. Early morning offshore breezes can clean up the small SSE swell, producing fun, groveling conditions on a groveler or longboard. The afternoons typically become windy and choppy. December is a month for small-wave gear and low expectations, but the occasional tropical or distant south storm can deliver a surprise pulse. Overall, it's a quiet finish to the year.