Cloud Cover API

Will it be clear tonight?

The Pxie cloud cover API tells you how much of the sky will be covered by cloud at any place on Earth, every 3 hours for the next 72 hours, with a plain label from Clear to Overcast.

Get an API key Quick start

Anywhere on Earth
72 hours, 3-hour steps
About 15 km grid

Base URL: https://api.pxie.ai · Auth: X-API-Key header · Format: JSON

Example, not a live reading

Jasper, Alberta · next 72 h

6%at midnight

Clear window tonight 21:00 to 09:00, then cloud builds Monday.

What you get

A cloud cover forecast API for the next 72 hours.

Total cloud in percent

How much of the sky is covered, from 0 to 100, for each 3-hour step out to 72 hours.

total_pct 6

A plain label

A 1 to 5 score with a word your users understand, from Clear to Overcast.

label Clear

Clear sky forecast windows

Group the low-cloud steps to tell people exactly when the sky opens up tonight.

21:00 to 09:00 · 12 h

Exact times

Every step carries a UTC timestamp and its hour from the forecast run, ready to convert to local time.

valid_utc 1792389600

Never silently old

Each response names its forecast run and age, and flags it as stale once it passes 20 hours.

stale false

Worldwide

Any latitude and longitude on Earth, from Jasper to the Atacama to Tekapo, on a grid about 15 km across.

coverage Global

Reading the numbers

From Clear to Overcast in five steps

The percentage is the number to build on. The label turns it into a word for your users, using fixed thresholds that never change between calls.

1 Clearunder 10%
2 Mostly clear10 to 30%
3 Partly cloudy30 to 60%
4 Mostly cloudy60 to 85%
5 Overcastover 85%

Quick start

Find tonight's clear window.

1
Get a keySign up and copy your API key from the dashboard.
2
Ask for the cloudSend a latitude and longitude to the cloud cover endpoint.
3
Show the windowJoin the clear steps into one "clear from … to …" answer.

curl -s "https://api.pxie.ai/v1/sky/cloud-cover?lat=52.87&lon=-118.08&hours=24" \
  -H "X-API-Key: YOUR_KEY"

const res = await fetch(
  "https://api.pxie.ai/v1/sky/cloud-cover?lat=52.87&lon=-118.08&hours=24",
  { headers: { "X-API-Key": "YOUR_KEY" } }
);
const { forecast } = await res.json();
// Longest run of Clear or Mostly clear steps
let best = [], run = [];
for (const f of forecast) {
  run = f.score <= 2 ? [...run, f] : [];
  if (run.length > best.length) best = run;
}

import requests

r = requests.get(
    "https://api.pxie.ai/v1/sky/cloud-cover",
    params={"lat": 52.87, "lon": -118.08, "hours": 24},
    headers={"X-API-Key": "YOUR_KEY"},
)
clear = [f for f in r.json()["forecast"] if f["score"] <= 2]

200 OKResponse (trimmed) · 3 credits
{
  "model_run": "20261018/12Z",
  "stale": false,
  "coverage": "Global",
  "forecast": [
    { "valid_utc": 1792368000, "total_pct": 64, "score": 4, "label": "Mostly Cloudy" },
    { "valid_utc": 1792378800, "total_pct": 22, "score": 2, "label": "Mostly Clear" },
    { "valid_utc": 1792389600, "total_pct": 6, "score": 1, "label": "Clear" },
    { "valid_utc": 1792400400, "total_pct": 4, "score": 1, "label": "Clear" },
    …
  ]
}

What your users see

Jasper · tonight

Clear from 21:00The sky opens up after sunset and stays clear until morning.

18:0064% · Mostly cloudy
Midnight6% · Clear
Forecast runToday 12Z
FreshnessUp to date

Hover a value to see the field it comes from.

Better together

Cloud is half the answer at night.

Aurora tonight?

Pair cloud with the aurora forecast: a strong display is no use behind an overcast sky.

Stargazing

Add seeing, transparency and moonlight with the astronomy weather API.

Dark enough?

Combine it with sunset and twilight times and the moon phase.

Ask in plain words

The same data answers questions in AI assistants through the Pxie MCP server.

Endpoints

Cloud cover endpoints.

Endpoint	What it returns	Credits per call	Plan
`GET /v1/sky/cloud-cover`	Total cloud in percent with a 1 to 5 label, every 3 hours to 72 hours.	3	Builder
`GET /v1/sky/conditions`	Cloud plus transparency, seeing, darkness, moon and a 0 to 100 observing score.	5	Builder
`GET /v1/sky/chart`	72-hour colour strip chart as a PNG image, in local time.	5	Builder

Every endpoint takes lat, lon and an optional hours (1 to 72). Credits are charged only for successful calls and cost the same over REST or MCP. Rate limits: 300 requests per minute on Builder, 1,200 on Scale.

Ask your AI assistant

"Will it be clear enough to see the aurora near Jasper tonight?"

Pxie answers with the get_sky_conditions tool. MCP access is included from the Builder plan. Environmental data MCP server →

Accuracy and limits

What to keep in mind

A forecast, not a sky camera. A grid about 15 km across can miss small or fast-moving clouds, and mountains and large lakes can make local cloud it does not capture.
Sharpest in the next two days. Accuracy falls with time, so trust the next 24 to 48 hours most and treat day three as a trend.
Total cloud only. Thin high haze and a thick low deck can read alike. Low, mid and high fields are filled only when the backup forecast is serving.
Fog and smoke are separate. Ground fog and wildfire smoke can hide the sky even when the cloud forecast is clear.

Questions

Cloud cover API FAQ.

Is the cloud cover API free?

Cloud cover is on the Builder plan and up, at 3 credits per call. The free plan covers light pollution, the moon, the sun and darkness.

How far ahead does the cloud cover forecast go?

Up to 72 hours, in 3-hour steps. Trust the next 24 to 48 hours most and treat day three as a trend.

Does it split low, mid and high cloud?

Usually not. The forecast gives total cloud cover. The low, mid and high fields are filled only when the backup forecast is serving, and are null otherwise, never guessed.

How often is the cloud forecast updated?

Each time a new forecast run arrives. Every response names the run it came from and how old it is, and sets stale to true once it passes 20 hours.

Does the cloud cover API work worldwide?

Yes. It takes any latitude and longitude on Earth, on a global grid about 15 km across.

Know when the sky opens up.

Cloud cover, the full sky forecast and MCP access are included from the Builder plan.

Get an API key See the quick start

Developers: cloud cover API docs →