Precipitation nowcast API

Quickstart

Get a free key (no card), then ask for a point. This asks for Amsterdam:

curl "https://nimboweather.com/v1/nowcast?lat=52.37&lon=4.90" \
  -H "X-API-Key: $NIMBO_KEY"

// Node 18+ or a server-side function: keep the key out of web pages
const res = await fetch("https://nimboweather.com/v1/nowcast?lat=52.37&lon=4.90", {
  headers: { "X-API-Key": process.env.NIMBO_KEY },
});
const data = await res.json();
if (!res.ok) throw new Error(`${data.error}: ${data.message}`);

console.log(data.summary?.text ?? "No radar coverage at this point");
for (const m of data.minutely.slice(0, 6)) console.log(m.time, m.precip_mm_h);

import os
import requests

r = requests.get(
    "https://nimboweather.com/v1/nowcast",
    params={"lat": 52.37, "lon": 4.90},
    headers={"X-API-Key": os.environ["NIMBO_KEY"]},
    timeout=10,
)
data = r.json()
if not r.ok:
    raise RuntimeError(f"{data['error']}: {data['message']}")

print(data["summary"]["text"] if data["summary"] else "No radar coverage at this point")
for m in data["minutely"][:6]:
    print(m["time"], m["precip_mm_h"])

The answer starts with a sentence you can show as it is, such as Light rain starting in 25 min, for about 40 min, then gives every step of the next hours.

Your key

Every call needs a key, except /v1/status (service health) and /v1/palettes (the colour tables of the tiles). Keys start with nimbo_. Send yours in one of three ways; they are equivalent:

• the header X-API-Key: nimbo_... (recommended);
• the header Authorization: Bearer nimbo_...;
• the query parameter ?key=nimbo_..., which map tiles require.

Keep the key on your server when you can. A key used in a web page or an app can be copied; if that happens, regenerate it from your dashboard. The old key stops working at once and your plan and usage are kept.

Request

GET /v1/nowcast

Every call counts as one call against your monthly allowance, whatever the horizon and step.

Response

A JSON object. The fields you will use most:

{
  "issue_time": "2026-11-12T17:10:00Z",
  "data_age_s": 420,
  "stale": false,
  "coverage": "radar",
  "radar_source": "opera",
  "lat": 52.37, "lon": 4.9,
  "summary": {
    "text": "Light rain starting in 23 min, for about 40 min",
    "rain_now": false,
    "rain_starts_at": "2026-11-12T17:40:00Z",
    "rain_ends_at": "2026-11-12T18:20:00Z",
    "minutes_until_rain": 23,
    "max_intensity": "light",
    "now_source": "radar"
  },
  "observed_now": {"time": "2026-11-12T17:15:00Z", "precip_mm_h": 0.0},
  "minutely": [
    {"time": "2026-11-12T17:15:00Z", "precip_mm_h": 0.0, "precip_probability": 0.05, "precip_type": "rain"},
    ...
  ],
  "attribution": ["..."]
}

This answer was made at 17:17 UTC: the forecast starts from the radar of 17:10, so its first entry (17:15) is already 2 minutes old, and minutes_until_rain (23) counts from 17:17.

The answer may carry more fields than these. Ignore the ones you do not use: new fields can be added at any time (see versions).

The summary

Rain means a rate of 0.2 mm/h or more, as published in minutely (rounded to 2 decimals, so an entry showing 0.2 is rain). The text speaks from the time of your request: “now” is the newest radar at the point when it is at most 15 minutes old (now_source: "radar", the same radar the map shows), else the forecast step nearest to your request (now_source: "forecast"). The reach it names (“in the next 3 hours”) is the length of the forecast, counted from its issue time: a request made a few minutes later has that many minutes less ahead of it, as the times in minutely show.

The text starts with the intensity at the start of the shower (the radar when it is raining now, else the shower’s first 30 minutes) and adds its peak when heavier (“Light rain (up to moderate)”), or “(lighter later)” when a shower of an hour or more ends lighter than it starts. max_intensity is the peak of the first shower: light (from 0.2 mm/h), moderate (from 2.5), heavy (from 10) or violent (from 50). Start times beyond an hour are rounded to 5 minutes (“in about 2 h 15 min”). The text is in English.

Steps

step only resamples minutely; the summary always reads the forecast every 5 minutes. With step=5 (the default) each entry is the forecast at its time. With step=1 the entries are interpolated linearly between the 5-minute values (the first 5 minutes repeat the first one: the forecast starts at issue time + 5 min). With step=10 or 15 each entry carries the largest value (rate and probabilities) of the 5-minute steps it covers, the minutes after the previous entry up to its own time, so a 15-minute entry never hides a 5-minute shower the text speaks of.

Data age and outages

When new radar data stops arriving, there is nothing new to forecast from, and the API says so instead of guessing:

• after 18 minutes without new radar data, stale becomes true;
• after 30 minutes, answers carry a notice and the status page shows the outage;
• after 2 hours, the API answers 503 with forecast_unavailable rather than serve an old forecast.

If rain matters to your users, show data_age_s or the notice.

Errors

Every error is JSON with a code you can test and a sentence you can log:

{"error": "out_of_coverage", "message": "This point is outside the forecast area."}

Some errors add fields, such as the quota on a 429. The ones to handle:

Limits and headers

Every answer to a call made with a key carries the state of your monthly allowance:

GET /v1/keys/me answers your key’s plan, monthly allowance and calls used this month. It is not counted, and it still answers once your calls have stopped.

On the Free plan, calls stop at 20,000 with a 429 until the month ends: no surprise bills. Paid plans keep working 10 % past their allowance, then stop the same way. Map tiles also have a short burst limit; a 429 from it carries only Retry-After (see tiles).

Attribution

On the Free plan, show “Rain forecast: Nimbo Weather” with a link to this site wherever you show the data. On every plan, also show the attribution field of the answer as it comes: it credits the radar data, as the data’s licence requires.

Versions

Questions or a field you need: [email protected].