What is Apple WeatherKit?
Apple WeatherKit is Apple's weather data service, introduced at WWDC 2022 as the successor to the Dark Sky API. After Apple acquired Dark Sky in 2020, it gradually transitioned Dark Sky's functionality into a new platform integrated with the Apple developer ecosystem. WeatherKit provides weather data to Apple's own Weather app on iPhone, iPad, Mac, and Apple Watch, and it is also available to third-party developers who want to build weather-powered applications.
WeatherKit is not a single weather model or a single data source. It is an aggregation platform that pulls forecast data from dozens of government meteorological agencies around the world, blends and refines that data using Apple's own processing, and delivers it through standardized APIs. This makes it one of the broadest weather data platforms available to app developers, covering virtually every populated location on Earth.
Where does WeatherKit get its data?
WeatherKit aggregates weather data from a global network of national meteorological services and government agencies. These are the same organizations that produce official weather forecasts for their respective countries. Apple maintains a public data source attribution page that lists its providers, which include:
United States
- NOAA (National Oceanic and Atmospheric Administration) provides the foundational observational data and numerical weather prediction models for the United States. NOAA operates the Global Forecast System (GFS), a global weather model that produces forecasts out to 16 days.
- National Weather Service (NWS), a division of NOAA, produces local forecasts, severe weather warnings, and watches for the US. NWS forecasters manually refine model output to produce the official public forecasts for each region.
International sources
- Environment and Climate Change Canada provides Canadian forecasts and severe weather alerts.
- UK Met Office provides weather data for the United Kingdom and is one of the world's leading numerical weather prediction centers.
- Deutsche Wetterdienst (DWD) provides data for Germany and contributes to European forecast models.
- Bureau of Meteorology (BOM) provides Australian weather data and tropical cyclone tracking for the southern hemisphere.
- Japan Meteorological Agency (JMA) provides data for Japan and is a major contributor to typhoon forecasting in the western Pacific.
- Dozens of additional agencies across Europe, Asia, Africa, and South America contribute regional data.
Apple blends data from these sources using its own algorithms to produce a unified forecast product. This means that WeatherKit's output is not simply a passthrough of any single agency's forecast. Apple applies post-processing to smooth transitions between data sources and to fill coverage gaps in regions where local agency data may be sparse.
The Dark Sky heritage
Before the acquisition, Dark Sky was known for its hyperlocal, minute-by-minute precipitation predictions. This capability, often called "next-hour precipitation," was based on high-resolution radar analysis that could predict rain starting or stopping at a specific location within the next 60 minutes. Apple carried this feature forward into WeatherKit, making minute-by-minute precipitation data available to developers and to Apple Weather users.
What data does WeatherKit provide?
WeatherKit offers a comprehensive set of weather data organized into several distinct datasets. Developers can request only the datasets they need, which helps manage API usage and keeps responses efficient.
Available datasets
| Dataset | Description | Typical use |
|---|---|---|
| Current conditions | Real-time temperature, humidity, wind, UV index, pressure, visibility, and condition description | Showing what the weather is right now |
| Hourly forecast | Hour-by-hour forecast for up to 10 days, including temperature, precipitation probability, cloud cover, wind speed and direction | Detailed timeline-based forecasts |
| Daily forecast | Day-by-day summary with high/low temperatures, precipitation amounts, sunrise/sunset times, and moon phase | Weekly overview and planning |
| Minute-by-minute precipitation | Precipitation intensity and probability for each minute over the next hour | Hyperlocal rain alerts and timing |
| Severe weather alerts | Government-issued watches, warnings, and advisories for a location | Safety notifications and emergency awareness |
| UV index | Current and forecasted UV radiation levels | Sun exposure guidance |
| Weather history | Historical observations for past dates at a location | Trend analysis and comparisons |
Each dataset includes metadata about the data source and the time the data was last updated, so developers can show users how fresh the information is. Severe weather alerts include the issuing agency, severity level, affected regions, and full alert text in the local language.
How developers access WeatherKit
Apple provides two methods for accessing WeatherKit, each suited to different development environments.
Native Swift framework
The WeatherKit Swift framework provides direct integration for apps running on Apple platforms: iOS, iPadOS, macOS, watchOS, and tvOS. Developers import the WeatherKit framework and use Swift's async/await syntax to request weather data for a given location. The framework handles authentication automatically using the app's provisioning profile, so there are no API keys to manage in the client code.
The Swift framework returns strongly typed model objects. For example, a request for hourly forecasts returns an array of HourWeather objects, each with properties for temperature, precipitation chance, wind speed, cloud cover, and UV index. This type safety makes it straightforward to build user interfaces directly from the data without manual JSON parsing.
REST API
The WeatherKit REST API provides access over standard HTTPS, making it available to any platform including Android, web applications, and server-side systems. Authentication uses JSON Web Tokens (JWTs) signed with a private key from the developer's Apple Developer account. The API returns JSON responses following a well-documented schema.
The REST API is useful for backend services that aggregate weather data, cross-platform apps that need weather data on non-Apple devices, and web applications that display weather information. It supports the same datasets as the Swift framework, with the same data freshness and global coverage.
Pricing and rate limits
WeatherKit is included with an active Apple Developer Program membership, which costs $99 per year. The free tier provides 500,000 API calls per month. Beyond that, developers can purchase additional capacity in tiers. Each API call can request multiple datasets (current conditions, hourly forecast, alerts) in a single request, so a well-designed app can serve a large user base within the free tier.
WeatherKit's privacy model
One of WeatherKit's distinguishing characteristics is its privacy architecture. Apple designed WeatherKit so that location data sent to the service is not linked to user accounts, Apple IDs, or device identifiers. When an app requests weather data for a latitude/longitude pair, Apple processes the request without associating it with any personal information.
This is a meaningful distinction from some competing weather data providers that monetize user location data or require user accounts for API access. Apple's approach means that an app built on WeatherKit can make a strong privacy claim: the weather service itself does not track where users are checking the weather, and the data pipeline does not create a location history tied to any individual.
For users who are privacy-conscious, this architecture means that choosing a WeatherKit-based app avoids one of the common data collection vectors in the weather app category, where some apps have historically sold or shared granular location data with advertisers and data brokers.
Which weather apps use WeatherKit?
WeatherKit powers a growing number of weather apps across the Apple ecosystem. Here are some of the most notable:
- Apple Weather is the built-in weather app on iPhone, iPad, Mac, and Apple Watch. It is the reference implementation of WeatherKit and the most widely used app built on the platform.
- Carrot Weather is a popular third-party weather app known for its customizable layouts, personality-driven interface, and support for multiple data sources. Carrot Weather offers WeatherKit as one of its data source options alongside others.
- Weathercaster is a chart-based weather app by Catspaw Systems that displays WeatherKit forecast data as interactive line charts. It shows temperature, cloud cover, precipitation probability, wind, and lightning risk on a single visual timeline for iPhone, iPad, and Apple Watch.
- Many other indie and commercial weather apps on the App Store have adopted WeatherKit as their primary or supplementary data source, drawn by its global coverage, privacy model, and the included free tier of API calls.
WeatherKit vs. other weather data providers
WeatherKit is one of several weather data platforms available to developers. Understanding how it compares to alternatives helps explain why different apps may produce slightly different forecasts for the same location.
OpenWeatherMap
OpenWeatherMap is a widely used weather API with a generous free tier. It provides global coverage and historical data. Its data sources include GFS, ECMWF, and local weather stations. OpenWeatherMap is popular for web and cross-platform applications, but it does not offer minute-by-minute precipitation or the same depth of Apple platform integration that WeatherKit provides.
Tomorrow.io (formerly ClimaCell)
Tomorrow.io uses a combination of government data, proprietary sensors, and machine learning models to produce forecasts. It is known for hyperlocal accuracy in certain regions and offers specialized APIs for industries like aviation, logistics, and insurance. Its pricing is typically higher than WeatherKit for comparable usage volumes.
National Weather Service API (US only)
The NWS provides a free, open API for US weather data. It is the authoritative source for US forecasts, watches, and warnings. However, it only covers the United States and its territories, and the API can be slower and less developer-friendly than commercial alternatives. Many apps use NWS data as a supplementary source alongside a global provider like WeatherKit.
Limitations and considerations
While WeatherKit is a strong platform, developers and users should be aware of some limitations:
- Minute-by-minute precipitation is not available in all countries. Coverage depends on local radar infrastructure and data sharing agreements.
- Forecast accuracy varies by region. WeatherKit performs best in areas with dense observation networks (like the US and Western Europe) and may be less precise in remote or data-sparse regions.
- Severe weather alerts depend on the issuing agency in each country. Some countries have more granular alert systems than others.
- Historical data availability varies by location and may not extend as far back as specialized climate databases.
- API rate limits require developers to design efficient caching strategies, especially for apps with large user bases.
Summary
Apple WeatherKit is a comprehensive weather data platform that aggregates forecasts from government meteorological agencies worldwide, delivers them through developer-friendly APIs, and protects user privacy by not linking weather requests to personal identifiers. It powers Apple Weather and a growing ecosystem of third-party apps. For users, choosing a WeatherKit-based app means access to globally sourced forecast data with a privacy-first architecture. For developers, it offers a reliable, well-documented, and competitively priced way to add weather data to any application.
