Tortoise Forecast

Weather for runners

The best running is outside.

Except when it’s a billion degrees. Or hailing.
Or there’s a thunderstorm coming.

Find the best time to run with Tortoise.

Get Beta Access

Free during beta · iPhone, iPad & Mac · Takes 30 seconds

The Today screen for Tokyo at dusk, under a violet sky: a run score of 9, Ideal, with sunset at 18:42 and 20 minutes until last light.
The Today screen for Nairobi in heavy rain under a cloudy sky: a run score of 7, Good, and a chart of the rain over the next hour, with 6 mm expected.

Why Tortoise

Regular weather apps
aren’t built for runners.

Your weather app tells you the temperature, but it doesn’t tell you what that actually means.

Is it going to feel hot and humid? Is the wind going to be pushing you about? Are you going to regret that long-sleeved hoodie after your first kilometre? Is that rain going to feel refreshing, or will you be shivering by the end?

No more guessing.

Tortoise Forecast checks everything that impacts your run, and lets you know the best time to head out. Think of it as that person who’s always telling you to go play outside, but with a PhD in meteorology.

Get Beta Access

How it works

Know before you go.

Find the best time to run

Tortoise looks at the day hour by hour and gives you the best time to head out. Sometimes that’ll be first thing in the morning before the heat comes on, and sometimes it’ll be a break between heavy rains.

Tomorrow: great running weather, but very hot in the afternoon. Best time to run from 4:00 to 8:00, with the temperature climbing from 14°C to 33°C.
Hour by hour from 5:00: scores of 9 until 7:00, then falling to 4 by 11:00 as it heats up.

One score for how your run will feel

Every hour gets a run score out of 10. It weighs up everything: how hot or cold it will feel, how strong the wind is, whether it’s going to be muggy or rainy. You can tell at a glance whether to go long or take it easy.

9, Ideal: near-perfect running weather.
5, Meh: it’s snowing, so take short strides to keep steady.
2, Terrible, on a hot and humid night: run by effort and hydrate well.

Advice in plain language

Numbers only tell you so much. Tortoise explains what the weather actually means for your run. Should you slow your pace a little? Bring water? Dress in layers? Or is it safer to wait it out a few hours?

Dangerous: dangerously hot, so take it very easy or skip your run. It feels like 39°C and it’s super humid, so take a little salt and a lot of water.
Today, 2 August: an okay 6, with thunderstorms from 15:00 to 18:00, so the best times to run are 14:00–15:00 and 18:00–20:00. Then great running weather tomorrow.

Plan your week

See the best days and times for the week ahead, so you can plan your runs around the good weather and avoid the worst.

A pink and violet sky with the sun just above the hills: sunset in 2 minutes, at 21:02, and last light at 21:35.

Catch the sunset

Find out how long you have until the light fades—and if you’ve got an opportunity for a magical sunset run.

Your runs: a 5 km run on 13 June, rated 8, and a 7.5 km run the day before, with a button to rate it.

Rate your runs

Rate your runs to help shape Tortoise’s recommendations. Your data stays on your phone unless you choose to share your ratings.

Coming soon

  • Home screen widget
  • Apple Watch app
  • Outfit ideas
  • Personalised recommendations

Help us test

Join our beta

  • Every Pro feature, free for the whole beta
  • Test out features before anyone else
  • Have a say in what we build next
Join on TestFlight

TestFlight is available for free on the App Store and will guide you through installation. You can leave the beta at any time.

If you have any questions or issues, send us an email.

Come running with us!

We ❤️ beta testers

We’re Sarah and Matt, and we’re both total run nuts. We built Tortoise Forecast so it would be easy for us to see everything we wanted to know before we put on our shoes on the way out the door.

Matt, grinning beside a pool at sunset.Sarah beside a lake, tongue out and fist in the air.

As a beta tester, you have the opportunity to shape the direction of Tortoise. We read every email ourselves. We use your feedback to decide what we build next. And if you have any questions or run into any troubles, we’re here to help out.

What did we miss?

FAQ

Is it free?
Yes, everything (including “paid” upgrades) is entirely free during the beta. We’ll keep you posted well in advance if that changes.
How do I join?
  1. Install TestFlight, Apple’s free beta app.
  2. Tap “Get Beta Access” below.
  3. Open Tortoise Forecast to plan your next run!
Get Beta Access
What if I don’t have TestFlight?
No problem! Tap “Get Beta Access” on your iPhone, iPad or Mac and Apple will walk you through installing it. It only takes about a minute.
I’m a beginner. Is this for me?
Sure is! We believe that running is for everyone. If you’re just getting started, we know (from years of experience!) how difficult it can be to figure out how the weather is going to impact you. We want to help you get out there and have a great time! If you run outside: we made this for you.
What devices does it work on?
It’s made for iPhone, since that’s what you’ll have with you on a run, but it works on iPad and on Macs with Apple silicon too. On iPhone and iPad, you’ll need iOS 18.5 or later.
How do I share feedback?
Send us an email or join our Discord. You can also send screenshots and feedback directly from the app via TestFlight.