How We Rate Surf Conditions
Our ratings are 100% data-driven, using real-time measurements from government ocean monitoring stations. No guessing, no opinions—just science.
1. Data Sources
We pull live data from three trusted government sources that continuously monitor ocean conditions:
NOAA Tides & Currents
National Oceanic and Atmospheric Administration
- Current water level
- Tide predictions (high/low times)
- 24-hour tide curves
NDBC Buoys
National Data Buoy Center
- Wave height (feet)
- Wave period (seconds)
- Swell direction (degrees)
- Water temperature
National Weather Service
NOAA Weather Forecasts
- Wind speed & direction
- Weather hazards
- Marine forecasts
Data Freshness
- Buoy data (waves, temp)Every 5 min
- Water levelEvery 5 min
- Weather conditionsEvery 30 min
- Tide predictionsEvery 1 hour
2. The Scoring System
Our rating starts at 100 points and deducts points for unfavorable conditions. This "subtractive" approach means perfect conditions score 100, and each negative factor reduces the score.
Final Score = 100 - Wind Penalties - Swell Penalties - Tide Penalties - Hazard Penalties + Ideal Condition Bonuses
Score is capped at
0 (minimum) and 100 (maximum)
3. Wind Scoring
Wind is one of the most important factors for surf quality. Offshore winds (blowing from land to sea) groom waves and create clean conditions, while onshore winds (sea to land) create choppy, messy surf.
| Wind Speed | Direction | Impact | Penalty |
|---|---|---|---|
| < 5 mph | Any | Glassy conditions | None (ideal) |
| 5-10 mph | Offshore (E, NE, ENE, ESE) | Clean, groomed waves | None |
| 5-10 mph | Onshore | Light texture on waves | -5 points |
| 10-15 mph | Offshore | Strong offshore, may be challenging | -5 points |
| 10-15 mph | Onshore | Choppy, textured waves | -15 points |
| 15-20 mph | Any | Windy, blown out conditions | -20 points |
| > 20 mph | Any | Dangerous winds | -30 points + HAZARDOUS |
Note: For California beaches, offshore winds typically come from the east (E, ENE, NE, ESE). The app automatically detects offshore vs. onshore based on wind direction.
4. Swell Scoring
Swell quality depends on two main factors: wave period (how long between waves) and wave height. Longer periods indicate groundswell from distant storms, which creates better-shaped waves.
Wave Period Quality
| Period | Swell Type | Wave Quality | Penalty |
|---|---|---|---|
| ≥ 12 seconds | Long-period groundswell | Excellent shape, powerful waves | None (ideal) |
| 10-12 seconds | Groundswell | Good shape, consistent sets | -5 points |
| 8-10 seconds | Mid-period swell | Moderate shape | -10 points |
| < 8 seconds | Wind swell / chop | Choppy, disorganized waves | -20 points |
Wave Height Assessment
| Wave Height | Description | Penalty |
|---|---|---|
| > 10 feet | Large dangerous surf | -20 points + HAZARDOUS |
| 8-10 feet | Large surf | -15 points (hazard warning) |
| 1-8 feet | Ideal surfing range | None |
| < 1 foot | Flat / barely surfable | -10 points |
5. Tide Scoring
Tide level affects wave shape and beach accessibility. Extreme tides can create hazardous conditions or make waves impossible to surf.
| Tide Level (MLLW) | Description | Penalty |
|---|---|---|
| < 0 feet | Extreme low tide | -15 points (shallow water hazards) |
| 0 - 1.5 feet | Low tide | -5 points |
| 1.5 - 5 feet | Mid tide (ideal range) | None |
| 5 - 6 feet | High tide | -5 points |
| > 6 feet | Very high tide | -10 points |
MLLW stands for Mean Lower Low Water—the average height of the lowest tide recorded each day over a 19-year period. It's the standard reference point for tide measurements.
6. Weather Hazards
Certain weather conditions create immediate safety risks that override other factors:
| Hazard | Risk | Penalty |
|---|---|---|
| Thunderstorm / Lightning | Life-threatening in water | -25 points + HAZARDOUS alert |
| Fog | Low visibility | -10 points |
| Rain (non-thunderstorm) | Reduced visibility | -5 points |
| Cold water (< 55°F) | Hypothermia risk without wetsuit | Hazard warning |
7. Spot-Specific Adjustments
Each surf spot has unique characteristics that affect how conditions translate to actual waves:
Swell Direction Window
Every beach faces a certain direction and can only receive swells from specific angles. A swell coming from outside the spot's "swell window" won't produce good waves at that location, regardless of its size.
Wave Height Coefficients
Some spots amplify or reduce swell. For example, The Wedge in Newport Beach has a coefficient of 1.3× because waves reflect off the jetty and create larger peaks.
Skill Level Considerations
At beginner-friendly spots, larger waves result in additional penalties since they're inappropriate for learning conditions. Advanced spots may penalize flat conditions more heavily.
Ideal Condition Bonuses
When conditions match a spot's ideal setup (correct wind direction, optimal tide, wave height in sweet spot), small bonuses are added—but the score is always capped at 100.
8. Example Calculation
Here's how a real rating might be calculated:
• Wind: 8 mph from ENE (offshore)
• Waves: 4 ft @ 11 seconds from SW
• Tide: 3.2 ft (mid-tide, rising)
• Weather: Partly cloudy, no hazards
Calculation:
Starting score:
100Wind (offshore, 5-10 mph):
-0Period (11s, good):
-5Wave height (4ft, ideal):
-0Tide (3.2ft, mid):
-0Weather hazards:
-0Final Score:
95 = GOOD
9. What We Don't Factor
Our rating focuses on measurable ocean conditions from buoys and weather stations. We intentionally exclude:
- Time of day / lighting — Dawn patrol often has the best conditions due to calm winds
- Crowds — Varies by day, time, and is subjective
- Local hazards — Rocks, rip currents, and reefs require local knowledge
- Beach access — Parking, stairs, and path conditions vary
Always assess conditions in person before entering the water.
Questions?
Our goal is complete transparency. The same algorithm runs for everyone—no hidden factors or manual adjustments. If you have questions about how a specific rating was calculated, the breakdown is always available in the app by clicking "Why this rating?" on any conditions card.