Iustin Nita
Founder & Runner, RunWeather
Iustin Nita is the founder of RunWeather and the runner who built it. After one too many summer runs fell apart at temperatures that looked fine on paper, he built RunWeather to translate weather into running effort: a 0-100 Run Score, dew-point-first forecasting, best-window timing, and pace context grounded in running research. He writes the RunWeather blog on dew point, heat, humidity, and training in the conditions you actually get.
He built RunWeather to translate the forecast into a 0-100 Run Score, the best window to run, and pace context grounded in dew point and running research, free on iPhone and Android.
Articles by Iustin Nita
- What to Wear for a Cold Marathon Start, by Goal Time
A cold race morning is three climates: corral, first 5K and finish. Throwaway layers, warm-up timing and race kit by goal time and start temperature.
- What to Wear Running in Cold Weather: Wind, Wetness and Waiting
Cold-run clothing from 50°F down to below 0°F (10 to -18°C), plus the changes for wind, rain, sun, pace and standing still that most charts leave out.
- How Cold Is Too Cold to Run? The Limit Is Wind Chill on Bare Skin
Every cold-running threshold you see quoted, reconciled into one position, plus typical and cold January mornings in US cities from NOAA's 1991-2020 normals.
- Running in the Dark: Reflectors on Your Joints Beat a Vest
What night-driving studies found about being seen, how the clock change moves your usual run into darkness city by city, and what to wear running in the dark.
- How We Price Race-Day Weather, and the Two Things We Got Wrong
What goes into the weather number on a RunWeather race plan, the two mistakes we found by checking it against real race results, what we changed, and how it now scores on 23 marathons.
- Same Temperature, Different Run: 684 City-Months of Running Weather Data
Two runs at 28.6°C can score 17 and 58. We scored every hour of the year in 57 cities to find out why temperature alone never explains a hard run, and how much the hour you pick is worth.
- Dew Point for Running: The Chart, and Why It Beats Humidity
Dew point running chart by band, workout and race distance, plus why dew point beats humidity: it measures the moisture that stops sweat from cooling you.
- Best Time of Day to Run in Summer: Read the Dew Point, Not the Thermometer
The best summer run time depends on dew point, sun exposure, and heat stored in pavement, not the air temperature alone. Here is how I choose between a morning and an evening run, hour by hour.
- How Much Does Heat Affect Running Pace?
Slow 1–3% once the dew point passes 55°F (13°C), 3–5% at 60–65°F, and 8% or more above 70°F (21°C): over 15 minutes on a 3:00 marathon.
- Hydration and Sodium for Hot Runs: A Dew Point-First Plan That Avoids Overdrinking
Humidity changes sweat cooling, not just sweat amount. Build a simple fluids + sodium plan by dew point, duration, and effort, with safety-first limits.
- Treadmill vs Outdoor Running: A Weather Decision Guide
Choose treadmill or outdoor running from the hazards, session purpose and available alternatives, with air-quality, indoor cooling and incline limits.
- What to Wear Running in Heat and Humidity: A Dew Point-First Gear Guide
Choose running clothing by dew point, sun exposure, and airflow. Learn fabric and fit principles that improve cooling and reduce chafing in humid heat.