New app: Yesterday, an iPhone app for yesterday’s weather #
21.20, Friday 28 Aug 2026
Link to this post I published my perfect iPhone weather app, and my guess is that you won’t want it.
Premise:
Why doesn’t my weather app tell me the weather yesterday?
I can never plan based on numerical temperature, etc. Am I going to be walking outdoors today? Should I take a jacket? Numbers are so abstract. Too much thought required.
HOWEVER: I can mostly remember what I wore yesterday.
So all I want to see, from my app, is: oh yeah today is like yesterday but a little warmer.
Then I can adjust easily.
I built an app around that core idea.
Yesterday features:
- Today’s weather is the solid line. Yesterday’s weather is the dashed line. The diff is arrows.
- Glanceable AI-generated text description using Apple’s built-in LLM.
- Dark mode! Tap the Sun to toggle dark mode (the Moon shows its current phase with latitude-accurate orientation).
Plus a home screen widget. And some little glyphs if there is a 30% of greater chance of precipitation. Nothing else.
Download Yesterday from the App Store. However my guess is that you won’t download it.
I vibed this app because it is the actual conversation that takes place in our kitchen every morning. Apple makes forecasts available via WeatherKit for free up to pretty generous limits.
So it has two users (we use it daily). Initially when I made it, I put the app on TestFlight for the two of us, and offered around on the socials to see if any of my friends would like it too.
In the old days (like, before May and the summer of vibe coding) there would have been a bunch of interest.
But now, instead: a handful of people came back with some enthusiastic variation of: yeah!! cool!! I made my own perfect weather app for me and my family just the other week too!!
I love this.
What this tells me is:
- Software has changed forever.
- We need more APIs (like WeatherKit) and underlying reliable databases with high-level operators (like whatever powers Photos or Reminders) and identity/permissions/etc, and that’s what an OS will have to include in the future.
- There needs to be
a protocol for discovering and sharing this new abundance of apps(April 2026). p.s. one of my testers (there are a few) pointed out that I forgot to add fahrenheit Oops! I’ll add that in the next version.
Yes Yesterday is like an old-fashioned barometer. The weather is like yesterday only more rain/more fair.
And cognitively it does seem more straightforward to take action by iterated adjustments based on a vector rather than deciphering an absolute value at every tick.
e.g. how about an automated savings account which, every month, always saves n+100 where n is the amount you squirrelled away last month, and your available actions are to ignore it (which means the savings transfers goes ahead) or adjust the modifier temporarily, but you can never simply keep it the same?
I wonder what a general rule could be? Like, building systems that always diverge and refuse to converge on steady state?