Outdoor Job Weather Window
Find the best hours this week to paint, mow, barbecue or walk, by clear weather rules.
Try an example: Paint the fence in Berlin · Mow the lawn in Amsterdam, two hours · Barbecue in Madrid, at least 18 °C
How it works
Checks the MET Norway forecast hour by hour against the rules of an outdoor job — temperature, humidity, wind, rain and dew point — and lists every window long enough to do it, including rain-free time afterwards for paint to cure or before mowing for the grass to dry.
- Fetches the MET Norway Locationforecast 2.0 for the place (rounded to 0.01°, cached until MET’s Expires time) and builds an hourly series; 6-hour steps after the first days are split into hours with interpolated values.
- Each hour inside the activity’s day hours is checked: no rain (≥ 0.1 mm per hour, ≥ 0.2 mm per 6-hour step or a rain chance ≥ 40 % count as rain), temperature, relative humidity and wind within the limits and, for painting, the air at least 3 K above the dew point (ISO 8502-4 asks this of the surface; air temperature stands in for it).
- Presets: painting 10–30 °C, ≤ 85 % humidity, ≤ 7 m/s, 4 hours plus 4 rain-free hours afterwards, 8:00–18:00; mowing 5–30 °C, ≤ 90 %, 2 hours with 3 dry hours before, 9:00–20:00; barbecue 14–32 °C, ≤ 8 m/s, 3 hours, 11:00–22:00; walk −5 to 28 °C, ≤ 10 m/s, 2 hours, 7:00–21:00. Your numbers replace the preset values.
- Runs of suitable hours are trimmed until the rain-free buffers hold and kept when they are at least the hours needed. The best window is the longest (earliest on a tie); the blocker count shows which rule failed most often.
A forecast window is a plan, not a promise: check the latest forecast and the paint maker’s instructions before you start.
Sources
- MET Norway Locationforecast 2.0 (api.met.no) (Norwegian Meteorological Institute (MET Norway))
- ISO 8502-4: Preparation of steel substrates before application of paints — Guidance on the estimation of the probability of condensation (surface ≥ 3 K above dew point) (ISO)
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How to use the Outdoor Job Weather Window
Find hours this week that suit exterior painting, mowing, a barbecue or a long walk, and understand why a sunny day can still fail the rules.
What it is for
Some jobs need more than "no rain". Paint must not get wet while it cures and should not go on when dew can form; grass cuts badly when it is still wet from a shower; a barbecue needs a few warm, calm hours in the evening. This tool checks every forecast hour from MET Norway against clear rules for one job and lists every window long enough to do it.
Four presets are built in — exterior painting, mowing, barbecue and a long walk or ride — and you can override the lowest and highest temperature, the highest humidity, the strongest wind and the hours you need. It plans with the forecast only; it cannot see your wall's surface temperature or how wet your lawn really is.
Worked example
Painting a fence in Sydney. Inputs: place -33.87, 151.21, time zone Australia/Sydney, activity Exterior painting or staining, 7 days. The painting preset asks for 10–30 °C, at most 85 % humidity, wind up to 7 m/s, the air at least 3 K above the dew point, four hours of work between 8:00 and 18:00 and four more dry hours afterwards.
The run on 7 November 2026 answered "Best window for exterior painting: 2026-11-13, 08:00–17:00 (9 h)". Two windows were found:
| Date | From | To | Hours | Temperature (°C) | Wind up to (m/s) |
|---|---|---|---|---|---|
| 2026-11-10 | 08:00 | 13:00 | 5 | 14.3 to 20.7 | 6 |
| 2026-11-13 | 08:00 | 17:00 | 9 | 19.3 to 22.2 | 6.8 |
The day-by-day table explains the rest of the week: on the 8th, 11th, 12th and 14th rain was the main obstacle; on the 9th there was no rain at all, but the wind stayed above 7 m/s, which blows dust into wet paint. The 10th had six suitable hours, five of which formed a window long enough for the job.
How to read the result
- Suitable windows lists each block in local time. To is when you should stop working, not when the paint is dry.
- Best window is the longest one; on a tie the earliest wins.
- Day by day shows how many hours passed every rule and the most common reason the others failed: rain, too cold, too hot, too humid, too windy or too close to the dew point.
- For painting, the windows already leave the four rain-free hours after the end; for mowing, the three dry hours before the start.
Tips and common mistakes
- Read the paint tin: if it asks for 8 hours rain-free, set fewer hours needed, or take the longer window.
- Morning windows for painting often fail on dew. Start after the dew has dried off, as the tool suggests.
- If nothing fits, the main obstacle tells you which limit to relax — for example a calm walk does not care about humidity.
- Windows in the 6-hour part of the forecast (from about day three) have rough edges; check again a day before.
- Use your own temperature limits for special products such as low-temperature paints.
FAQ
Why is a sunny day rejected?
Usually the wind or the dew point. Sunshine is not one of the rules; temperature, humidity, wind and rain are.
What does the dew-point rule do?
Coating guidance (ISO 8502-4) asks for a surface at least 3 K above the dew point, so no condensation forms under the paint. The tool uses the air temperature as a stand-in for the surface.
How far ahead does it look?
Up to nine days, as far as the MET Norway forecast reaches. Hourly steps cover the first two to three days.
Is the forecast data free to use?
MET Norway publishes it under CC BY 4.0; every result carries that attribution.
Guide last updated:
For scripts and AI agents
- JSON API:
POST https://hearthweatherwindow.usefulweb.app/api/v1/calculate(same calculation as this page) - Interface description: OpenAPI 3.1 · AI guide: llms.txt
- MCP server (Streamable HTTP):
https://hearthweatherwindow.usefulweb.app/mcp· tool namehearth_weather_window
Example request
curl -s -X POST https://hearthweatherwindow.usefulweb.app/api/v1/calculate \
-H 'content-type: application/json' \
-d '{"place":"52.52, 13.40","timeZone":"Europe/Berlin","activity":"painting","days":7}'