# Today's and tomorrow's spray window

> Type a town and see, hour by hour, when wind, gusts, Delta T, humidity, rain and thermal inversion allow spraying. Free, no sign-up.

- Canonical URL: https://pulvecast.com/spray-window
- Language: en
- Last updated: 2026-11-01
- Path: Home › Today's and tomorrow's spray window
- Site guide for agents: https://pulvecast.com/llms.txt

**Short answer:** Pick a town and the tool colours the next 48 hours with the PulveCast app's default limits: wind and gusts up to 25 km/h, Delta T 2 to 8 °C, humidity 55 to 95 %, rain chance up to 50 % and no thermal inversion. The first run of green hours is your next spray window.

_The tool needs JavaScript. The PulveCast app runs the same check, hour by hour, for 7 days._

## How the tool decides

Each hour gets the worst colour among the parameters below, the same rule as the app. Green is safe to spray, yellow is caution and red is do not spray.

| Parameter | Green | Yellow | Red |
|---|---|---|---|
| Wind and gusts (10 m) | up to 22.5 km/h | 22.5 to 25 km/h | above 25 km/h |
| Delta T | 2.2 to 7.2 °C | 2 to 8 °C | below 2 or above 8 °C |
| Relative humidity | 60.5 to 85.5 % | 55 to 95 % | below 55 or above 95 % |
| Rain chance | up to 45 % | 45 to 50 % | above 50 % |
| Rain forecast in the hour | 0 mm | up to 0.5 mm | above 0.5 mm |
| Thermal inversion (T80 m − T2 m) | 0 °C or less | up to 1.5 °C | 1.5 °C or more |
| Temperature | up to 36 °C | 36 to 40 °C | below 0 or above 40 °C |
| Weather type | no fog or rain | fog | drizzle, rain or thunderstorm |

The wind limits suit ground equipment and most drones; each spray drone has its own limit on the [spray drones](https://pulvecast.com/drones) page. For the reasoning behind each limit, see the guides on [Delta T](https://pulvecast.com/guides/delta-t), [wind speed](https://pulvecast.com/guides/wind-speed-for-spraying), [thermal inversion](https://pulvecast.com/guides/thermal-inversion) and the [best time to spray](https://pulvecast.com/guides/best-time-to-spray).

## What the app adds

- The next 7 days, not only 48 hours, with the spray windows already listed.
- Your drone's or machine's limits and those of the selected crop.
- Drift risk by nozzle droplet class, and a warning when the wind blows towards a marked sensitive area.
- An alert before each window opens, Kp and satellites for the drone's RTK, and the application log.

## Frequently asked questions

### Where does the forecast come from?

From Open-Meteo, the PulveCast app's default source, for the exact point of the chosen town and in its local time.

### Is dead calm good for spraying?

Not always. Calm air that is colder near the ground often means a thermal inversion, which keeps fine droplets in the air. The tool estimates the inversion from the temperature difference between 80 m and 2 m; when it shows up, the hour turns yellow or red even without wind.

### Can I rely on the forecast alone?

No. The forecast helps you plan the day, but the final decision is made in the field: measure wind, temperature and humidity at release height and follow the product label.

## Check the spray window before you go to the field

PulveCast gives a green, yellow or red verdict for every hour from Delta T, humidity, wind, gusts, drift risk and thermal inversion. Free on Android and iOS, no account needed.

- Google Play: https://play.google.com/store/apps/details?id=com.pulvecast.app
- App Store: https://apps.apple.com/app/pulvecast/id6779816829