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Surf forecast for Rio Mearim

Tide
⏱️s.
⚡️kJ
Timezone:
America/Fortaleza
Forecast updated:
20/06, 15:00
Wind: SN UNITY Atmos
(20260620 18z)
Waves: SN UNITY WAVE
(20260620 18z)
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Timeline

Tomorrow Sun 21/06 to Mon 22/06
No surf windows (2 days)
Unlock 3 more days in the timeline
More surf windows and day entries continue below

Rio Mearim Surf Forecast Guide

Rio Mearim is a laid-back surf spot located in a beautiful area that’s a bit off the beaten path. This spot is a mix of river and ocean vibes, making it unique for surfers. It's about a 3-hour drive from Arari, which is known for its watermelon. The journey from the river mouth, also known as the Cement Mix, to the Arari village offers a variety of waves to ride over about 1.5 hours.

The surf here can cater to different skill levels, especially beginners. The waves break primarily on a sandy bottom, and you can catch rights and lefts depending on the swell. The optimal swell direction is from the northeast, while you can also find some action with swells coming from the southwest and southeast. On a good day, the waves can reach up to 2.5 meters (8ft), but they're also manageable at around 0.6 to 0.9 meters (1 to 2ft), making it easier for new surfers to get comfortable. The best time to catch some morning waves is usually from around 5 to 10 am during low tide.

Keep in mind that the water can be pretty fun to ride when the conditions align. With a variety of spots along the river, you can find something that suits your vibe. Just be aware that conditions can change, so it's good to check the surf before heading out. Enjoy your time at Rio Mearim!

Surf spots near Rio Mearim

São Marcos
State of Maranhão, Brazil
Unknown break
Sun 21
Mon 22
Tue 23
Wed 24
Thu 25
Ponta d'Areia
State of Maranhão, Brazil
Unknown break
Sun 21
Mon 22
Tue 23
Wed 24
Thu 25
Sao Marcos
State of Maranhão, Brazil
Beach break
Sun 21
Mon 22
Tue 23
Wed 24
Thu 25
Calhau
State of Maranhão, Brazil
Unknown break
Sun 21
Mon 22
Tue 23
Wed 24
Thu 25
Rio Mearim
Maranhão, Brazil
Rivermouth break
Sun 21
Mon 22
Tue 23
Wed 24
Thu 25

Frequently asked questions

What are good surfing conditions for Rio Mearim?

Rio Mearim is usually best with swell from southwest to southeast (SW-SE), ideally northeast (NE) around 0.6 m / 2 ft to 2.4 m / 8 ft and low tide. Low tide is the preferred tide.

Where is the surf spot Rio Mearim?

Rio Mearim is a surf spot in Arari, Maranhão, Brazil.

What is the surf break like at Rio Mearim?

Rio Mearim is a left-and-right rivermouth break over sand. Expect a fairly quiet crowd.

What surfing skill level is Rio Mearim suitable for?

Rio Mearim can suit beginner surfers.

Is Rio Mearim beginner friendly for surfing?

Yes. Rio Mearim can suit beginner surfers when conditions are manageable.

How consistent is the surf at Rio Mearim?

Rio Mearim has moderate surf consistency for Maranhão, Brazil.

What surf spots are near Rio Mearim?

Other nearby surf spots are Ponta d'Areia, São Marcos, Sao Marcos, and Calhau.

What swell direction works for surfing at Rio Mearim?

Rio Mearim can work with swell from southwest to southeast (SW-SE); northeast (NE) is usually best.

What swell size works for surfing at Rio Mearim?

Rio Mearim usually works with swell around 0.6 m / 2 ft to 2.4 m / 8 ft.

What tide works best for surfing at Rio Mearim?

Rio Mearim works best around low tide. Low tide is preferred. A rising tide is usually better here.

Readme

Welcome! If you’re new to surf forecasting, check out this quick guide.

Forecast Table

The forecast table (the section on the page with all the numbers) is designed to pack as much information in the screen as possible. Although intimidating at first, it will help you make informed decisions about the waves faster, trust me :D. The table consists of roughly four sections, time and predictions, wind, waves, and tides:

🔮 Time and predictions section

Here we show the forecast thour and the overall surf quality prediction. This is determined based on the wave, wind and tide quality prediction. These individual predictions can be found on the forecast map.

💨 Wind section

The first row on the table (with the 💨 icon) shows wind speed, direction and gust. The more the wind speed the more aggressive the color (from blue, green, orange to red).

🌊 Wave section

The waves section consists of three rows, one for wave height and direction, one for period and one for wave energy. Our algorithm chooses the "dominant wave" using spot-adjusted surf energy (depth + directional fit). This is usually the first swell partition, but during local storms it can switch to wind waves. If that happens, values are shown in gray and italic.

🌒 Tide section

The tide section consists of a row with the actual heights per hour (measured at the half hour) and a table that displays the flow of the tide and the extremes (lows and highs).

Forecast map

The forecast map consists of arrows. These arrows represent all wave partitions (swell partitions and wind wave partition) and the wind. This allows you to see things like: a secondary swell or wind waves messes up the surf, or the wind is just a tick offshore so very surfable. Click a metric label in the bottom left to bring that arrow to the front — handy when arrows overlap.

Forecast Cheat Sheet

Short on time? Focus on wave energy. It’s the best single metric to gauge how big and powerful the waves will be.

Click any table cell to jump to that forecast hour. The map will update with forecast arrows, so you can see if wind and swell direction are lining up.

Use the table sidebar to switch units for height and speed.

Log your surf sessions to compare forecasts with real sessions and sharpen future predictions.

Models and Updates

Surfnerd blends multiple global and local wind and swell models using advanced interpolation and spatial techniques to create an "ensemble" forecast. Forecasts are refreshed hourly.

Surf Predictions

Our AI-driven algorithm scores surf quality, shown by green, orange, and gray dots. Each forecast hour is rated for wind, swell, and tide quality, then combined into an overall score. Here’s the scale:

Perfect
Good
Average
Bad or No Data

Session logs also feed the algorithm — the more you log, the smarter your forecasts get.

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Confidence

Confidence tells you how much the weather models agree on the forecast.

  • High confidence: Models agree closely; forecast is reliable.
  • Medium confidence: Some disagreement; conditions may shift slightly.
  • Low confidence: Models diverge; treat forecast with caution.

We calculate the wind confidence by comparing wind speed, gust and direction from multiple models (like GFS, ECMWF, Arome, and Harmonie) and seeing how closely they match. For wave certainty we compare height, period and direction, also on multiple models. They are weighted, meaning that some models count more than others, depending on how good they are for a certain spot.

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