Reading a
Great Lakes
Forecast
The lake doesn't send invitations. You have to learn to read the signs.
Ocean surfers have it easy. Consistent swells, reliable buoy networks, and forecasts that hold for days. On the Great Lakes, the window between “nothing” and “firing” can be as narrow as six hours. Learning to read a forecast isn't just helpful here — it's the difference between scoring the session of the season and showing up to a flat lake.
The Wind Rose
Not all wind directions are created equal. On Lake Michigan's west shore, direction is everything.
Wind direction determines whether you get clean, rideable surf or a chaotic mess. The compass below shows how each direction affects conditions on the west shore of Lake Michigan. Northerly and southerly winds push along the lake's longest axis, building the most powerful swells. Westerly winds blow offshore, grooming existing waves. Easterly winds create short-fetch chop that's rarely worth paddling out for.
Legend
Best Swell Builders
N, NNW, NNE — Pushes along the full 307-mile fetch
Good Swell
S, SSW, SSE — Solid fetch, reliable surf
Offshore Grooming
W, WNW, WSW — Cleans up existing swell beautifully
Poor — Cross-Lake
E, ENE, ESE — Short fetch, onshore mess
This diagram is calibrated for Lake Michigan's west shore (Wisconsin/Michigan). East shore surfers should flip E/W ratings.
Understanding Fetch
Fetch is the distance wind travels over open water. More fetch means bigger, more organized waves.
On the ocean, fetch is essentially unlimited. On Lake Michigan, it's a precious and finite resource. The lake is roughly 307 miles long but only 80 miles wide. This means a north or south wind has nearly four times the distance to build waves compared to an east or west wind. Understanding this geometry is the single most important concept in Great Lakes forecasting.
Lake Michigan Fetch Lines
Fetch Distance → Wave Height
How fetch length translates to wave potential (at 25kt sustained wind)
Key Insight: A 25kt north wind produces roughly 2.5x the wave height of a 25kt east wind on the west shore. Fetch is the multiplier that makes Great Lakes surf possible.
Reading a Buoy Report
NOAA buoys are your eyes on the lake. Here's how to decode the data.
The National Data Buoy Center (NDBC) operates several buoys on the Great Lakes. Station 45007 (south Lake Michigan) and 45002 (north Lake Michigan) are your two best friends. Each report contains five critical numbers that tell you everything you need to know about current conditions.
WVHT
4.2 ft
Significant wave height — average of the highest 1/3 of waves
DPD
8 sec
Dominant wave period — time between wave crests
MWD
350°
Mean wave direction — where the waves come from
WSPD
22 kt
Sustained wind speed — average over 8 minutes
WTMP
41°F
Water temperature — determines wetsuit choice
Good Day vs. Bad Day
North wind pushing long-fetch swell with a solid 8-second period. Waves are organized and the period indicates they've traveled and cleaned up. Moderate wind keeps it manageable.
East wind means short fetch and onshore slop. The 4-second period tells you these waves are wind-driven chop with no organization. High wind speed makes it dangerous without producing rideable surf.
The 48-Hour Window
Great Lakes swells are born fast and die fast. Here's the typical lifecycle of a surf event.
Unlike the ocean, where a swell can travel thousands of miles over several days, Great Lakes surf events happen in compressed timelines. A storm system can go from “nothing on radar” to “head-high waves” in 24 hours — and back to flat within 48. You have to be watching, ready, and willing to move fast.
Watch For
The wind-to-swell transition at hours 18-24. When the buoy period jumps from 4s to 6s+, the swell is organizing. Start driving.
Sweet Spot
Hours 30-40 are usually prime. The swell is fully developed but the wind is starting to back off or shift offshore. This is when glass happens.
Don't Miss It
Great Lakes swells decay fast without continuous wind energy. If the forecast says the wind drops at midnight, the morning session may already be small.
Swell Period Matters
Wave height gets all the attention. But period is the real indicator of surf quality.
A 4-foot wave at 5 seconds is a completely different animal than a 4-foot wave at 9 seconds. Short-period waves are wind-driven — they're steep, close together, and break erratically. Long-period waves have had time to organize — they're spaced apart, they feel the bottom earlier, and they break with power and predictability. Period is the hidden metric that separates a “meh” session from a “best day of the year.”
Short Period (4-6 sec)
●Wind-driven chop, waves stacked on top of each other
●Steep faces with no clean wall to ride
●Hard to predict where they'll break
Long Period (8-12 sec)
●Organized swell with well-defined sets
●Clean, open faces with room to turn
●Predictable peaks and consistent lineups
Period Quality Scale
On the Great Lakes, anything above 7 seconds is considered excellent. A 10-second period is rare and legendary — the kind of day you tell stories about for years.
Wind Speed Decoder
What different wind speeds actually mean for surf conditions on the lake.
Wind speed is simple in theory — more wind equals bigger waves. But in practice, there's a sweet spot. Too little and the lake stays flat. Too much and it's dangerous, blown-out chaos. The magic range for surfable Great Lakes conditions is narrower than you might think.
Mirror-flat conditions. Beautiful for kayaking, stand-up paddleboarding, or photography. Zero surf potential. Great for scouting spots and studying the bottom contours you'll never see on a surf day.
Small surf possible if wind has been blowing for 6+ hours along a long fetch. Expect knee-high to waist-high waves at best. Longboard territory. Great conditions for beginners learning to read waves without risk.
This is where the magic happens. Enough energy to build real swell — chest-high to overhead — without overwhelming the lake. Period starts climbing above 6 seconds. With proper fetch alignment and 12+ hours of duration, this produces classic Great Lakes surf.
Overhead to double-overhead potential, but conditions are raw and dangerous. Heavy wind chop on top of swell. Only experienced surfers with heavy wetsuits should consider paddling out. Key strategy: find spots protected by structure (piers, points, harbor walls) that block the onshore wind while focusing the swell.
Gale-force conditions. The lake becomes a whitewater machine. Waves are massive but completely unsurfable — blown out, closing out, and genuinely life-threatening. This is storm-watching territory. Find a high bluff, bring a camera, and respect the power. The surf will be epic the day after, when the wind drops.
Putting It All Together
A decision flowchart for calling a session. Follow the arrows.
When a storm system appears on the forecast models, run through this checklist. Every “yes” increases your odds of scoring. Hit all four gates and you can be confident it's worth the drive.
Remember: This flowchart is a starting point, not gospel. Local knowledge, spot-specific factors (protection from wind, bottom contour, tide-like seiches), and your own experience level all matter. When in doubt, drive to the lake and look. Some of the best sessions happen when the forecast says “marginal.”
Pro Tips
Hard-earned wisdom from surfers who've been reading this lake for decades.
“Don't trust a single model. I check GFS, NAM, and HRRR. When they agree, I clear my schedule. When they disagree, I wait for the next run.”
“Watch the pressure gradient, not just the wind forecast. A tight gradient over the lake means sustained energy even if the wind numbers don't look spectacular. Loose gradients produce gusty, inconsistent wind that never builds real swell.”
“The best sessions are often 6 to 12 hours after the wind peaks. Everyone checks the webcam during the storm and sees blown-out chaos. They go to sleep. The early birds who check at dawn get the leftover swell with offshore wind. That's the real secret.”
“Lake Michigan has a memory. After a big north blow, the swell wraps into coves and harbors for hours after the open coast goes flat. Know your secondary spots and you can extend a session by half a day.”
“November through February, check the water temperature trend. When the lake is below 40°F and the air is even colder, you get sea smoke. Beautiful to look at, dangerous to surf in — you can't see incoming sets. Wait for it to burn off.”
Essential Forecasting Tools
NDBC Buoy Data
Stations 45007, 45002, 45024
Great Lakes Coastal Forecasting
GLERL wave model predictions
Windy.com / Windguru
GFS, ICON, and ECMWF wind models
NWS Surface Analysis
Pressure maps and frontal analysis
Continue Learning
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