GrayCloud vs Tomorrow.io
The short version
Tomorrow.io (formerly ClimaCell) is an enterprise weather API. It is the commercial alternative many ex-Dark Sky developers evaluated first when the Dark Sky API shut down in March 2023. Its pitch is proprietary nowcasting at scale, satellite-derived radar in radar-sparse parts of the world, and tiered API pricing aimed at businesses.
GrayCloud is a consumer weather app for iPhone, Apple Watch, Mac, and the web, built on a Dark Sky-shaped JSON backend with a public API tier on the roadmap. It is not a sales-led enterprise product. If you are a developer who wanted to keep paying a flat-ish Dark Sky-style fee for a weather endpoint and ended up bouncing off Tomorrow.io's pricing, GrayCloud's eventual API will be a closer fit.
Feature-by-feature
| Aspect | Tomorrow.io | GrayCloud |
|---|---|---|
| What it is | Enterprise weather API + dashboard | Consumer app + roadmap API |
| Audience | Businesses, ops teams, developers at scale | End users; developers in time |
| Consumer app | No (web dashboard for ops) | Yes - iPhone, Apple Watch, Mac, web |
| Dark Sky-shaped JSON | No - own schema | Yes - drop-in shape |
| Forecast pipeline | Proprietary blend + nowcasting | Proprietary multi-model engine |
| Minute-by-minute precipitation | Yes - proprietary nowcast | Yes - in-house nowcasting engine, national radar feed |
| Pricing | Tiered, sales-led for production | Free on Apple devices and web. Pro subscription. API tier on roadmap. |
| Migration path from Dark Sky | Schema rewrite required | Hostname swap when API ships |
| Public accuracy scoreboard | No | Yes (scored nightly) |
The migration problem
The reason a lot of indie developers bounced off Tomorrow.io after Dark Sky's shutdown is mundane: the JSON shape is different. A Dark Sky integration written in 2018 expects `currently.temperature`, `hourly.data[i].precipProbability`, `daily.data[i].temperatureHigh`. Tomorrow.io speaks `timelines[i].intervals[i].values.temperature` and a completely different field layout. Migrating means rewriting parsers, retesting, and re-validating units.
GrayCloud's backend already speaks the Dark Sky dialect - same field names, same shape, same unit conventions. When the public API tier ships, the migration is a hostname swap, not a schema rewrite. If you have surviving Dark Sky parsing code, it will work.
The models, briefly
Tomorrow.io's value proposition is a proprietary global blend with their own nowcasting layer, with a particular emphasis on filling radar gaps internationally using satellite-derived precipitation estimates. For genuinely radar-sparse parts of the world, that has real value.
GrayCloud's forecast engine is a proprietary blend built on best-in-class numerical weather data sources for the parts of the world they cover well. Where those underlying sources are strong, GrayCloud is competitive on accuracy - and verified nightly on a public scoreboard. Where they aren't (parts of the world without good radar coverage), a global commercial product like Tomorrow.io may genuinely fit better.
The pricing problem
Tomorrow.io's free tier exists but is bounded; production use moves quickly into sales-led pricing. For a side project or a small SaaS that just wants ten thousand forecast calls a month, that is friction.
GrayCloud's eventual API tier is planned around a Dark Sky-style flat pricing model - predictable, hobbyist-friendly at the bottom, scaled by volume rather than by sales conversation. No timeline commitment yet; the consumer app comes first.
When to choose Tomorrow.io
- You are at a business with real volume, an ops use case, and a procurement process.
- You need worldwide minute-by-minute coverage including parts of the world with sparse radar.
- You are willing to rewrite parsers and want the most production-tested proprietary nowcasting.
- You need an SLA on the API.
When to choose GrayCloud
- You want a weather app for iPhone, Apple Watch, Mac, or the web.
- You are an indie developer or solo builder who valued Dark Sky's flat pricing and predictable schema.
- You are content with US-focused minute-by-minute today and a global hourly/daily outlook.
- You want a public accuracy scoreboard and no analytics tracking.
Try GrayCloud
Or open the web app - type an address at /forecast for a forecast in any browser, no install required.
See also: the Dark Sky alternative overview · vs Dark Sky · vs Apple Weather.