A weather API is an Application Programming Interface that allows software to retrieve weather data automatically.
Instead of manually looking up weather information on a website, an application can send a request containing a location, date or date range, and the type of weather data required. The API then returns structured data that the application can process.
Weather APIs are commonly used to retrieve:
- Historical weather
- Current conditions
- Weather forecasts
- Temperature
- Precipitation and snow
- Wind speed and direction
- Humidity and dew point
- Atmospheric pressure
- Cloud cover and visibility
- Solar radiation
- Weather alerts and events
- Other environmental information
Weather data can then be incorporated into applications, websites, spreadsheets, databases, analytics systems, machine-learning models, or automated business processes.
How does a weather API work?
Most modern weather APIs use standard HTTPS requests.
A typical request identifies:
- The location
- The required date or date range
- The weather variables required
- The desired units
- The response format
- An API key that identifies the account making the request
For example, a weather application might request the forecast for London:
https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/London,UK?unitGroup=metric&key=YOUR_API_KEY
The server processes the request and returns structured weather data.
A simplified JSON response might look like:
{
"resolvedAddress": "London, England, United Kingdom",
"timezone": "Europe/London",
"days": [
{
"datetime": "2026-08-21",
"tempmax": 23.1,
"tempmin": 14.8,
"precip": 0.2,
"windspeed": 18.4,
"conditions": "Partially cloudy"
}
]
}
Software can then use those values without requiring a person to manually read or copy the weather information.
What is a REST weather API?
Many weather APIs are REST APIs.
REST APIs use standard web technologies such as:
HTTPS
URLs
GET or POST requests
JSON
CSV
This makes them accessible from almost any modern development environment.
For example, a weather REST API can be called from:
- Python
- JavaScript
- Java
- C#
- PHP
- Go
- Ruby
- Swift
- R
- MATLAB
- Command-line tools such as cURL
- Microsoft Excel and Power Query
- Google Sheets
- Database and ETL systems
You do not normally need a special weather-specific programming library. If a programming language can make an HTTPS request and process JSON or CSV, it can generally use a REST weather API.
Historical weather, current conditions, and forecasts
Weather APIs can provide several different types of weather information.
Historical weather
Historical weather describes conditions that occurred in the past.
For example, an application might request:
London, UK
July 1-31, 2026
and retrieve daily or hourly weather for that period.
Historical weather is useful for:
- Business analytics
- Insurance analysis
- Agricultural research
- Energy modeling
- Transportation studies
- Machine learning
- Retail analysis
- Academic research
- Investigating past events
Current conditions
Current conditions describe the most recent weather available for a location.
Applications might use current conditions to display:
- Current temperature
- Humidity
- Wind
- Precipitation
- Visibility
- Cloud cover
- Weather conditions
Current conditions are commonly used by websites, mobile applications, operational dashboards, and automated systems that respond to current weather.
Weather forecasts
Forecast weather describes expected future conditions.
Forecasts can be used for:
- Scheduling
- Staffing
- Transportation
- Logistics
- Agriculture
- Construction
- Energy demand
- Event planning
- Inventory planning
- Weather-sensitive operations
A well-designed weather API can make historical, current, and forecast data available through a consistent interface.
Why use a weather API?
A weather website works well when a person simply wants to check the weather.
A weather API becomes useful when software needs the weather automatically.
For example, suppose a retailer wants to determine whether weather affects daily sales.
The company could retrieve historical weather for each store and combine that information with sales records:
date
store
sales
temperature
precipitation
snow
conditions
The resulting dataset can be analyzed to determine whether temperature, rain, snow, or other conditions affect customer behavior.
Because the data is retrieved programmatically, the same process can be repeated for many locations and dates.
Add weather to an application
Applications frequently use weather APIs to add weather-aware features.
For example, a travel application might retrieve the forecast for a destination.
A transportation application might evaluate:
precipitation
snow
visibility
wind
temperature
before planning a route.
An agricultural application might monitor:
temperature
precipitation
humidity
solar radiation
for agricultural locations.
Weather becomes another source of information that application logic can use when making decisions.
Add weather to business data
One particularly useful application of a weather API is enriching an existing dataset.
Suppose a company has records containing:
location
datetime
sales
Historical weather can be added:
location
datetime
sales
temperature
precipitation
conditions
The company can then investigate relationships between business performance and weather.
The same technique can be used with:
- Insurance claims
- Road accidents
- Equipment failures
- Deliveries
- Customer visits
- Energy consumption
- Agricultural yields
- Construction delays
- Maintenance records
- Operational incidents
This is sometimes called weather-data enrichment.
Automate weather data retrieval
Weather APIs are also useful when weather data needs to be refreshed automatically.
For example, an application could retrieve a forecast every morning and use it to update:
- Staffing recommendations
- Delivery schedules
- Energy predictions
- Inventory requirements
- Agricultural operations
- Outdoor work schedules
Because the process is automated, the application can react to changing weather without requiring someone to manually check a forecast.
Use weather data in Excel and spreadsheets
You do not have to be a software developer to use a weather API.
Microsoft Excel, Power Query, and Google Sheets can retrieve weather data directly from an API.
A spreadsheet can therefore combine business data with weather information such as:
Date Sales Temp Precip Conditions
08/17 12,450 84.1 0.00 Clear
08/18 9,820 72.4 1.24 Rain
08/19 11,930 78.6 0.08 Cloudy
This makes weather API data useful for analysts as well as software developers.
What information can a weather API provide?
Weather APIs differ in the data they make available.
Common weather elements include:
Temperature
Examples include:
temperature
maximum temperature
minimum temperature
feels-like temperature
dew point
Precipitation
Examples include:
precipitation amount
precipitation probability
rain
snow
snow depth
Wind
Examples include:
wind speed
wind gust
wind direction
Atmospheric conditions
Examples include:
humidity
pressure
cloud cover
visibility
weather conditions
Solar and astronomical information
Some weather APIs also provide:
solar radiation
solar energy
UV index
sunrise
sunset
moon phase
moonrise
moonset
Specialized APIs can also provide additional environmental information such as weather alerts, severe-weather events, air quality, marine conditions, radar information, and wildfire activity.
Daily, hourly, and sub-hourly weather
Weather data can also be provided at different time resolutions.
Daily weather
Daily data summarizes the weather for an entire calendar day.
Typical values include:
maximum temperature
minimum temperature
total precipitation
maximum wind speed
average humidity
daily conditions
Daily data is useful for long historical datasets and higher-level analysis.
Hourly weather
Hourly data provides significantly more detail.
It can be useful when the timing of weather matters—for example, identifying whether rain occurred during business hours rather than simply knowing that rain occurred sometime during the day.
Sub-hourly weather
Some applications require observations or forecasts at intervals shorter than one hour.
Sub-hourly data can be useful for areas such as:
- Energy
- Solar analysis
- Agriculture
- Transportation
- Equipment monitoring
- High-frequency operational analysis
The appropriate resolution depends on the application.
Weather API locations
A weather API should make it easy to request weather for the locations used by an application.
Common location formats include:
London, UK
New York, NY
20190
38.9697,-77.385
Depending on the API, locations can include:
- Cities
- Addresses
- Postal or ZIP codes
- Latitude and longitude
- Weather stations
- Other geographic identifiers
Latitude and longitude are particularly useful when applications already contain geographic coordinates.
JSON or CSV weather data
Two common Weather API output formats are JSON and CSV.
JSON
JSON works especially well for applications because it can represent structured and nested information.
For example:
{
"days": [
{
"datetime": "2026-08-21",
"tempmax": 82.4,
"tempmin": 64.2
}
]
}
JSON is commonly used by:
- Web applications
- Mobile applications
- Backend services
- Python applications
- JavaScript applications
- Java and .NET applications
CSV
CSV works well when the desired result is a flat table.
For example:
datetime,tempmax,tempmin,precip,conditions
2026-08-21,82.4,64.2,0.0,Clear
2026-08-22,79.8,65.1,0.3,Rain
CSV is especially convenient for:
- Excel
- Databases
- Data warehouses
- Statistical tools
- Data science
- Bulk analytical workflows
The best format depends on how the application will use the data.
How do weather APIs get their data?
Weather information can come from many different sources.
These can include:
- Official weather stations
- Airport observations
- Mesonet stations
- Radar
- Satellites
- Numerical weather prediction models
- Government meteorological agencies
- Other observational and forecast datasets
A weather API provider typically processes these sources and makes the resulting weather information available through a consistent interface.
This is important because raw weather sources can vary significantly in format, update frequency, spatial coverage, and time resolution.
A weather API removes much of that complexity from the application developer.
What makes a good weather API?
When evaluating a weather API, there are several important factors to consider.
Historical coverage
If your project uses historical weather, determine:
- How far back the data extends
- Which countries and regions are supported
- Whether daily and hourly data are available
- How missing observations are handled
- Which weather variables are available historically
Forecast coverage
For forecast applications, consider:
- Geographic coverage
- Forecast horizon
- Update frequency
- Time resolution
- Available weather elements
- Sources and models
Current conditions
If current weather matters, determine how frequently the data is updated and how the provider selects and combines observation sources.
Available weather elements
Make sure the API provides the variables required by your application.
A basic application might need only:
temperature
precipitation
conditions
while a specialized application may require:
solar radiation
snow depth
wind gust
visibility
pressure
humidity
weather alerts
Location support
Check whether the API can accept the types of locations your application uses, such as:
- Coordinates
- Cities
- Postal codes
- Addresses
- Station identifiers
Data formats
JSON and CSV support make a weather API easier to integrate into a wide range of applications and analytical systems.
Documentation
Good API documentation should explain:
- How to authenticate
- How to specify locations
- How to specify dates
- Available weather fields
- Units
- Response formats
- Error codes
- Usage limits
- Working code examples
Clear documentation can substantially reduce the time required to build and maintain an integration.
Reliability and scalability
Production applications should also consider whether the API can support their expected request volume and operational requirements.
Pricing and usage limits
Weather API plans can vary significantly in how usage is measured and what features are included.
Consider:
- Request or record limits
- Concurrency limits
- Historical-data access
- Forecast access
- Specialized data availability
- Commercial-use requirements
- Support requirements
Because pricing and plan features can change, always review the current pricing and licensing information rather than relying on numbers quoted in older tutorials.
What is the Visual Crossing Weather API?
The Visual Crossing Weather API provides historical weather, current conditions, and forecast weather through the Timeline Weather API.
The basic Timeline request structure is:
/timeline/[location]/[date1]/[date2]
For example, a forecast request for London can use:
/timeline/London,UK
A historical request can add a date:
/timeline/London,UK/2026-07-01
or a date range:
/timeline/London,UK/2026-07-01/2026-07-31
The same API structure can therefore be used for many common historical and forecast workflows.
Customize a Weather API request
A Visual Crossing Timeline request can be customized using parameters such as:
unitGroup
include
elements
contentType
For example:
unitGroup=metric
selects metric measurements.
include=days,hours
requests daily and hourly information.
elements=datetime,temp,precip,windspeed,conditions
limits the response to selected weather fields.
contentType=json
requests JSON output.
This allows an application to retrieve only the information it actually needs.
Try a Weather API without writing code
If you want to explore weather data before building an integration, Visual Crossing provides tools that let you select locations, dates, weather variables, units, and output formats interactively.
This can be useful for understanding the API request and response before writing any application code.
You can also use Visual Crossing Weather Data to explore and download weather information.
Get started with the Visual Crossing Weather API
The simplest way to start is:
- Sign up for a free Visual Crossing account.
- Obtain your Weather API key.
- Choose a location.
- Select the dates and weather data you need.
- Run a Timeline Weather API request.
- Use the returned JSON or CSV in your application.
Visual Crossing plans include usage and request limits, so applications should operate within the limits of the account plan being used.
For a complete walkthrough, see How do I get started with the Weather API?.
For the complete API reference, see the Timeline Weather API documentation.
Summary
A weather API lets applications retrieve weather information automatically using standard web requests.
Weather APIs can provide:
- Historical weather
- Current conditions
- Forecast weather
- Daily, hourly, and sub-hourly data
- Temperature
- Precipitation
- Wind
- Humidity
- Snow
- Solar information
- Alerts and environmental events
They can be used from programming languages, spreadsheets, databases, websites, applications, ETL systems, and analytics platforms.
For organizations that need to incorporate weather into software or business data, an API provides a repeatable and automated alternative to manually looking up weather information.
The Visual Crossing Timeline Weather API provides historical, current, and forecast weather through a consistent interface, making it possible to use the same integration for a wide range of weather-data applications.