Running in Cold Weather: Why Your Pace Slows (And Why It Doesn't Matter During Base Training)

I find that when I try to run in the cold weather that it's difficult to maintain the same pace compared to either running in warmer weather and/or inside on a treadmill.

For example, last week on Monday/Tuesday it was in the 50's and 60's it was easy to maintain a 7:10 pace or so for a 7 mile run.

On the weekend, it was about 20 degrees and I found it very difficult to get close to that pace. I've noticed this on other warm/cold days too.

When I run on the treadmill I always have the incline set to either 1.5 or 2 degrees to compensate for the outside/inside differences.

Even when I ran competitively in HS and college I would never do as well racing on cold days. I always felt it was a strain to maintain what should have been certain paces.

Is there a scientific reason for this that anyone is aware of?

For my second question about "Base Running Phase." There's a lot of talk about building a base. How long should the base running phase last? Do you worry about running pace when in this phase, or is the main concern just logging miles? How do you know how many miles is enough?

Thanks,
Tom – Tom, Arlington Heights, Illinois, USA

Answer by Dom: Tom, there is a real physiological reason your 20°F pace falls apart — you're not imagining it. Stop chasing 7:10 in the cold, run by effort instead, and treat your base phase as a patient 8–12 week build of easy mileage.

1. Why Cold Weather Slows Your Pace
2. How to Run Well at 20°F
3. Does Pace Matter During Base Training?
4. How Long the Base Phase Lasts and How Many Miles Is Enough

Why Cold Weather Slows Your Pace

Cold works against you in four ways. Your muscles and tendons are stiffer and less elastic, so each stride gives back less spring and costs more energy. Your body narrows the blood vessels in your skin and limbs to protect core heat, so less warm blood reaches your legs. Cold, dry air irritates your airways, so breathing feels harder at the same effort. Add heavier clothing and a shorter, more guarded stride on slippery ground. Same effort, slower pace.

Your numbers fit this perfectly. You held about 7:10 per mile for 7 miles (roughly 11 kilometres) in 50–60°F weather, then struggled at around 20°F — about 30 degrees colder. At the same effort, expect to run noticeably slower at 20°F than at 50–60°F — the exact amount varies from runner to runner, so I won't pin a number on it. So a pace somewhat slower than 7:10 is your 7:10 equivalent, and that's a good run, not a bad one. Your racing history backs this up. You felt the strain on cold race days in high school and college because it was genuine strain.

How to Run Well at 20°F

Warm up before you leave the house. Spend 10–15 minutes indoors with a brisk walk, leg swings and a few easy jogs up and down the hallway. Then start your first mile slower than feels necessary.

Dress as if it were 10–15°F warmer than the thermometer says. At 20°F, wear what you'd wear at 30–35°F. You should feel slightly cold for the first five minutes. Wear a thin moisture-wicking base layer (never cotton), a light mid layer, a windproof outer layer, plus hat and gloves.

Then run by rate of perceived exertion (RPE), the 1–10 effort scale where 1 is very easy and 10 is all-out. Aim for 4–5 on easy days — you can speak full sentences without gasping. If your breathing climbs before your pace visibly drops, ease off. Slippery ground also shortens your stride and lifts your cadence (your steps per minute), and I covered the same reader's cadence question in a separate answer.

One gentle clarification on your treadmill. Treadmills show incline as a percent grade, not degrees. 1.5–2 degrees would be a steep 2.6–3.5 percent, so I suspect you mean 1.5–2 percent. That's sensible — 1 percent is the usual setting to mimic outdoor wind resistance, so you're being slightly generous. Keep it, but run by effort indoors too.

Does Pace Matter During Base Training?

No. Base training is easy, conversational running that builds your aerobic engine — your body's ability to use oxygen for steady work. Time and miles matter. Pace doesn't. I cover the full base training approach separately, and why pace isn't the target metric during base training goes deeper on the effort side.

Watch for junk miles in winter. These are miles that leave you too tired for your next session. A 7-mile "easy" run into a 20°F headwind can land far harder than your training log suggests. If it felt hard, slow down or shorten it, and keep the next day easy.

How Long the Base Phase Lasts and How Many Miles Is Enough

The full range runs from about 4 weeks to 6 months, depending on how far away your goal race is. For a fit ex-racer who already runs 7 miles comfortably, I'd plan on 8–12 weeks. You aren't starting from zero, so you don't need the long end. For sizing it to your own race date, see how to size your base phase to your goal race.

Start from the weekly mileage you manage comfortably now. Add no more than 10 percent a week, and take a consolidation week every 3–4 weeks, dropping mileage by 20–30 percent. As an example only, from 25 miles a week: 25, 27, 29, 23, 27, 29, 31, 24. The rules and cutback weeks are in the full mileage-progression rules and cutback weeks.

How many miles is enough? Enough when you've held your goal race's weekly mileage for 2–3 weeks, your easy runs feel easy, and you have no niggles. As a rough guide, that's 25–35 miles a week for a 5K or 10K, and 35–45 for a half marathon or marathon.
Tom, run by effort on cold days, give yourself 8–12 weeks of patient easy mileage, and the pace will come back when the weather warms. Enjoy the build-up :)

Kind regards,
Dom

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