How Grip works
Grip estimates the state of the rock, hour by hour, for each wall. It models the two things that make sea-cliff rock greasy: water on the surface, from rain, spray, sea salt drawing moisture out of damp air, or condensation on rock colder than the air's dew point; and how fast the air, wind and sun can dry it again. Each daylight hour collects points from the factors below, which are turned into a 0 to 10 index. The three weather models are scored separately and blended, with the Met Office 2 km model weighted highest for the first two days. A day's score is its best three-hour window; the number of climbable hours and the wet-rock risk are shown alongside.
What Grip does not tell you
Grip scores friction: how dry and grippy the rock is likely to be, from weather and sea forecasts. It is a guide, not a guarantee, and it can be wrong.
It does not tell you whether the sea is safe, and it does not cover freak waves, tide times, loose rock or rockfall, access, how hard a route is, or your own ability. Nesting birds are covered only as far as the bird register goes, and it is not a definitive record.
Crag facts such as aspect, tide, shelter and birds come from guidebooks and climbers’ reports. They may be out of date or wrong. If you find one that is, send a crag note.
Climbing and moving around sea cliffs carry a risk of serious injury or death. You are responsible for your own decisions: look at the rock and the sea when you arrive, check the tide times, and turn back if in doubt.
Grip is a free, non-commercial project, provided as is, with no promise that it is accurate or always available. Use it at your own risk.
Scoring factors
| Factor | Points | Why |
|---|---|---|
| Air moisture | +1 for every 4% below 76% humidity (up to +4 at 60%) and -1 for every 5% above (down to -4), with an extra -1 once humidity passes 75%. The penalties count in full when the rock is within 2°C of the dew point and at half when it is 4°C or more clear | Sea salt on the rock starts drawing water out of the air at about 75% humidity. Humid air greases rock through condensation, so the penalty is tied to how close the rock is to the dew point: logged days showed dry rock in 80% air climbing well. Below 76% the reward was steepened after logged days showed the rock keeps improving as the air dries. |
| Haar | Fog on the Met Office 2 km model or visibility under 1 km -4; patchy fog or visibility under 4 km -2 | Sea fog soaks the rock directly and stops any drying. It also adds to the water on the rock (0.1 mm an hour in thick haar, half that in patchy), so the rock stays damp after the haar lifts until the air and wind have dried it. |
| Rock against dew point | Rock temperature minus dew point: 0 or less -4, up to 1°C -3, up to 2°C -2, up to 3°C -1, over 5°C +1 | Rock sweats when it is colder than the dew point. Rock temperature is estimated from the current air temperature (40%) and the last 24 hours' average (60%), pulled 30% towards the sea temperature (60% at tidal walls, which stand in it), warmed by up to 3°C when the sun is on the face, and cooled by 1.5°C under a clear sky with little wind when the sun is below 15 degrees or gone. That covers warm damp air after a cold spell, cold-sea sweating in spring, dew at dawn and the damp that arrives as the sun leaves a face. |
| Wind direction | -1 straight onshore, +1 straight offshore, 0 along the shore, with the effect shrinking to nothing in a calm (full from 15 km/h) | Onshore air is moist and salty. The Aberdeenshire coast counts as facing east-south-east, the Banff and Moray coast as facing north. |
| Wind strength | Under 5 km/h -1, 5-15 +1, 15-35 +2, over 35 +1. At sheltered walls at the back of a bay the speed is halved unless the wind blows onto the face; in a narrow inlet it is halved from every direction. Onshore wind over 25 km/h -1, over 40 km/h -2. Positive points are halved while the rock is wet | Wind clears damp air off the rock and speeds drying, but a gale onshore carries spray. |
| Sun | Cloud 0, sun +1, sun on the face +3 (+2 when the sun is under 10 degrees up). Halved while the rock is wet | Direct sun warms the rock above the dew point and dries it. On the face means within 60 degrees of the wall's aspect. |
| Sea state | 1.5 m+ -2, 0.8 to 1.5 m -1, 0.3 to 0.8 m 0, under 0.3 m +1 | Spray wets the rock and lays down fresh salt. Waves from behind or along the face count at 40%, or 70% for long-period swell, which wraps round headlands. In narrow inlets the swell funnels and reflects, so the height counts 1.5 times from any direction; walls protected by offshore rock count it at half. |
| Water on the rock | Raining -5. Otherwise, by the water left on the rock: over 0.5 mm -3, 0.1-0.5 mm -2, a trace -1 | The film is tracked hour by hour. Rain adds to it, up to 2 mm; a big sea (over 2.5 m, or 2 m at tidal walls) adds a little spray; and at 85%+ humidity the salt draws in a thin brine film of up to 0.15 mm. It dries at a rate set by the vapour pressure deficit (how much more moisture the air can take), the wind and sun on the face. Shelter is not applied here: logged days show sheltered rock still dries at the full rate in dry air. Humid, still air barely dries it; warm, breezy, sunny air clears a light shower in two or three hours. This is what makes the morning after a humid night greasy until the air dries. |
| Seepage | 5 mm+ of rain in the last 24 hours -2, 10 mm+ -3, a further -1 for 25 mm+ in the last three days | Drainage after heavy rain lasts much longer than surface water. |
| Dry rock | Up to +2 when there is no water on the rock, no rain, no haar and the rock is 3°C or more above the dew point: the full +2 at 76% humidity and above, fading to nothing at 60%, where the air reward already covers it | Dry rock on a grey day is good rock. Without this, an overcast calm morning with nothing wrong scored Greasy; logged days said Grippy. The calm-air penalty is also waived when the rock is dry and the air is under 80%. |
The index is 3 plus half the points, held between 0 and 10. Hours with the sun less than 5 degrees above the horizon are not scored. Tides are shown for planning but not scored, and so are nesting birds: a crag in its bird season is marked, not marked down. Model disagreement is shown rather than hidden: striped cells and the wet-rock risk tell you when the forecasts differ. The weightings are a first estimate and are being checked against real days; expect them to change.
Weather models
Models in the latest run, Wed 21 Oct, 05:52: Met Office, ECMWF, ICON.
Checking Grip against real days
21 logged days scored so far. Taking the score as shown, Grip landed in the felt band 8 times, and within a point of it 16 times. Misses are measured on the unrounded score from the edge of the band, since the form records a band rather than a number: typical miss 0.9, on average 0.1 below the felt band.
By model: Met Office in the band 9 of 21, typical miss 1.1 (below by 0.3); ECMWF in the band 9 of 21, typical miss 1.0 (below by 0.1); ICON in the band 8 of 21, typical miss 0.9 (above by 0.3); Actual weather in the band 8 of 21, typical miss 1.0. The model that lands in the band most often over enough days is the one to trust most in the blend. The actual-weather column scores the day from the ERA5 reanalysis, the best record of what the weather really did, so it tests the scoring logic itself rather than the forecasts.
| Date | Crag | Felt | Grip | Met Office | ECMWF | ICON | Actual weather |
|---|---|---|---|---|---|---|---|
| 17 Oct 2026 | Yellow Crag | Grippy (6 to 7) | 8 Prime | 8 | 8 | 8 | 8 |
| 16 Oct 2026 | Brown Band Crag | Prime (8 to 10) | 8 Prime | 8 | 8 | 8 | 8 |
| 13 Oct 2026 | Boltsheugh | Grippy (6 to 7) | 5 Climbable | 5 | 4 | 5 | 4 |
| 11 Oct 2026 | Meikle Partans | Climbable (4 to 5) | 3 Greasy | 2 | 4 | 6 | 2 |
| 11 Oct 2026 | The Round Tower | Grippy (6 to 7) | 2 Greasy | 0 | 3 | 7 | 3 |
| 10 Oct 2026 | Johnsheugh | Climbable (4 to 5) | 8 Prime | 8 | 8 | 8 | 8 |
| 10 Oct 2026 | Murray Heugh | Climbable (4 to 5) | 7 Grippy | 7 | 6 | 7 | 6 |
| 6 Oct 2026 | Murray Heugh | Grippy (6 to 7) | 7 Grippy | 7 | 7 | 7 | 7 |
| 6 Oct 2026 | The Orchestra Cave | Grippy (6 to 7) | 7 Grippy | 7 | 6 | 8 | 7 |
| 3 Oct 2026 | Clashrodney | Grippy (6 to 7) | 6 Grippy | 7 | 4 | 6 | 4 |
| 3 Oct 2026 | Drab Crag | Grippy (6 to 7) | 7 Grippy | 7 | 6 | 7 | 6 |
| 3 Oct 2026 | Green Slough | Climbable (4 to 5) | 3 Greasy | 2 | 3 | 6 | 3 |
| 1 Oct 2026 | Craig Stirling | Grippy (6 to 7) | 6 Grippy | 6 | 6 | 6 | 6 |
| 27 Sep 2026 | Newtonhill (Backdoor Wall) | Climbable (4 to 5) | 3 Greasy | 4 | 3 | 1 | 4 |
| 26 Sep 2026 | Craig Stirling | Climbable (4 to 5) | 6 Grippy | 7 | 6 | 6 | 6 |
| 26 Sep 2026 | Logie Head | Prime (8 to 10) | 7 Grippy | 7 | 8 | 8 | 8 |
| 19 Sep 2026 | Green Slough | Grippy (6 to 7) | 6 Grippy | 6 | 6 | 6 | 6 |
| 19 Sep 2026 | Logie Head (2 logs) | Grippy (6 to 7) | 7 Grippy | 7 | 7 | 8 | 8 |
| 13 Sep 2026 | Brown Band Crag | Grippy (6 to 7) | 4 Climbable | 4 | 5 | 4 | 5 |
| 13 Sep 2026 | Brown Crag | Climbable (4 to 5) | 6 Grippy | 6 | 7 | 6 | 7 |
| 22 Jul 2026 | Souter Head (Grassy Pinnacle South Wall) | Greasy (2 to 3) | 6 Grippy | 5 | 5 | 6 | 6 |