Sending temps: how to fuel a cold day on rock
Every climber loves sending temps. Crisp air, sticky rubber, skin that lasts all day. What gets less attention is that cold days quietly change the fueling job, and a lot of strong efforts fade early because nobody adjusted.
Here's what changes when the temperature drops, and how to pack for it.
Cold costs energy, even standing still
Your body spends real energy just staying warm at the base, between burns, and on the descent. A cold crag day burns more fuel than the same day in September, and the deficit sneaks up because you're not doing anything that feels like work. The fix is simple: bring more food than the same day would need in warm weather, and eat it on schedule rather than waiting for hunger, because cold also blunts appetite. On a cold day, hunger is a lagging indicator.
The thermos is a piece of gear
A thermos of something hot changes the entire day. Options, in ascending order of ambition:
Tea or coffee. The minimum. Warms hands, raises morale, keeps you drinking (more on that below).
Hot chocolate made with soy or oat milk. Warmth, quick energy, and protein in one pour. Kids' drink reputation, elite crag performance.
Soup or dal. The full move. A thermos of lentil soup or dal at midday on a freezing belay ledge is one of the great luxuries available to any climber at any budget. Lentils bring protein and slow-burning warmth, and it beats a frozen sandwich by a distance that can't be measured.
Cold food strategy
Some warm-weather staples fail in the cold. Energy bars turn to bricks. Chocolate finally becomes viable. Adjust accordingly:
Keep soft, sticky fuel (dates, energy balls) in an inside jacket pocket so body heat keeps it eatable.
Wraps and burritos survive cold better than sandwiches; stash one near your back panel rather than the frozen top of the pack.
Nuts, trail mix, and dried fruit are indifferent to temperature. They're the reliable middle class of the cold-weather pack.
The hydration trap
Nobody feels thirsty at 4°C. You're still losing water all day, especially breathing hard on cold, dry air, and dehydrated forearms pump faster. Treat drinking as a schedule, not a sensation: some water or hot tea between every burn or two. If you use a hydration bladder, know that the hose freezes before anything else does; bottles stored upside down (ice forms at the top) are the cold-day standard.
The rhythm of a well-fueled cold day
Big hot breakfast at home. Graze early and often, on schedule. Something hot and real at midday. Sticky fuel from the warm pocket between afternoon burns. Hot drink for the pack-up and the walk out.
Fuel like that and sending temps get to be what they're supposed to be: an advantage. The skin lasts, the rubber sticks, and the engine stays warm enough to use them.
