Climbing Conditions: 101

That sweet southern sandstone can be a real fickle lady.

In the O.G. Horse Pens 40 guidebook, Adam Henry explained that the notoriously sandbagged grades are tuned for ideal conditions and perfect beta. This is, obviously, the purest way for the rock to tell us its true number grade (i.e. subtract 2 V-grades from all boulder problems).

And yet, a solid rain shower, some gusty winds and a timely cold front really can make those greasy slopers feel like sticky jugs.

Let’s skip the friction coefficients and geology and ask the obvious question:

Is the rock wet?

>tl;dr climbing weather conditions are 99% about how wet that particular condition makes the rock.

Rain

Rain isn’t always our natural enemy; rain showers clean grease and chalk off the rock naturally, without the need for pressure washers and brushes. If I were to dream up the perfect weather conditions for southern sandstone, a well-timed shower right before the trip is definitely primo.

Of course, precipitation is easy enough to read from a forecast. What we actually want to learn is how long it will take for wet rock to dry.

Here’s the single most useful indicator of wet rock I was ever told: on the drive up the mountain, if the road is still wet the closer you get to the parking lot, the rock is probably still wet. Obviously puddles are too wet, but ideally those dark, damp spots would be on their way to drying out, too.

Porosity and Permeability in Rock Climbing

Water retention of rock is usually discussed in terms of how porous or how permeable the rock is. Porous rock holds water like a sponge; impermeable rock doesn’t let the water penetrate well, so it remains on the surface.

That last one sounds like a bad deal for climbing, but it could mean the water will find it’s way out quicker. Porous rock, like sandstone, might be dry on the surface while retaining water internally, which makes it highly susceptible to flaking and damage. Certain places like Red Rock Canyon strictly prohibit climbing for day(s) after a rain shower, lest ye risk permanently destroying a classic jug or a crimpy flake. Always respect the local etiquette and if in doubt, pull down not out.

Humidity

Air wetness incurs rock wetness; but counter-intuitively, drier isn’t always better. This research suggests that fingertips have the best friction when conditions are dry, but not too dry.

If conditions are too dry, it’s a perfect opportunity to look super sick, and get a little moisture on the fingertips, via the french [sic] blow (SFW):

Wind

If the first day of your trip does get some unfortunate rain clouds, your best chance is to hope for strong, sustained winds to blow-dry the rock. If the proj is high up on a mountain or particularly exposed, you might expect more wind than usual.

Average wind speeds probably mean faster moving clouds, which means conditions could change faster. Higher gust speeds might mean a lucky gust or two could really speed up the entire drying process. However, in a crag with lots of tall vegetation, gusts of wind rattle the leaves every now and then and shower the rocks below; it’s hard to say for certain what the effects could be, but I’m generally bullish on strong winds.

Send Temps

So, why are cold temps better for climbing? The most important reason is summed up by humidity’s less-popular step-brother, Dewey point.

Dew Point

In short, warmer air can hold more water (as vapor). Dew point (°F) takes this into account, and therefore can more accurately compare the amount of air-wetness on any given day than relative humidity.

For example, if Tuesday and Wednesday have the same apparent temperature of 70°F, you can directly compare their relative humidity values, since they’re relative to a given temperature.

Otherwise, cool air at 50% water capacity (i.e. humidity) will always hold less water than warm air at 50% capacity. That’s why dew point is crucial for comparing different days and different crags.

Rubber

Frankly, the worst part about climbing in the ice-cold is taking off warm, wool socks and jamming my feet in some stiff, undersized lady slippers (I have a slim mid-sole). That’s why

Fresh Tips #2: in cold temps, stash your climbing shoes in your jacket for the approach. When you get to the proj they’ll be toasty from your body heat, and warmed up and ready for climbing.

Some people do the Lion’s Breath, blow-hot-moist-air thing into the shoe, and that’s cool, too. I guess.

Did you know that rubber traditionally comes from trees?

But, most modern climbing shoes are made from synthetic compounds and blends

… that are synthesized from petroleum byproducts?

Anyway, rubber sticky == climb good. This excellent article about friction and climbing says that climbing shoe manufacturers intentionally design their rubber compounds to reach optimal senditude between 0° and 5°C (32° - 41°F), simply because you sweat the least in that range.

Sweat (& Blood & Tears)

Lower temps mean your tips will probably sweat less. That’s all. Climbing shoe manufacturers apparently picked 0-5°C for optimal rubber performance because that’s the Goldilocks temperature for our hands: cold enough to prevent sweating, but not so cold that you can’t warm up.

Fresh Tips #3: when my V-crusher buddy arrives at the boulder field, he’s already chalking and warming up his hands. That way, if he starts feeling some holds on the way to the proj, he’s not leaving behind grease bombs. Legend.

Conclusion

More in-depth analysis is sure to come. But most climbers will benefit from the single, unsurprising takeaway that crispy climbing conditions are mostly about wetness.

Find crispy condies and more at rockclimate.com.