Department of Health

Beaufort wind scale for pesticide spraying

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Key messages

  • The Beaufort scale is a measure that relates wind speed to observed conditions at sea or on land.
  • Pest control operators need to be aware of wind conditions at the time of application, as some conditions are not ideal for spraying pesticides.
  • Ideal spraying conditions are at wind speeds of 6–19 km/hr, which equates to a Beaufort number of 2 or 3.

The Beaufort scale is a measure that relates wind speed to observed conditions at sea or on land. It can be used in place of a wind-measuring instrument to assess the suitability of the weather conditions for spraying.

Pest control operators need to be aware of wind conditions at the time of application as some conditions are not ideal for spraying pesticides.

Table 1 outlines different wind speeds and their corresponding Beaufort number, and how these conditions relate to pesticide spray application.

Wind speed and pesticide spray advice

Table 1: Beaufort scale and pesticide spraying conditions

Beaufort number

Wind speed

Description

Spray notes

0

<1km r="">

<1 knot="">

Calm: smoke rises vertically

Avoid fine sprays,

especially on warm, sunny days

1

1–5 km/hr

1–3 knots

Light air: wind direction shown by smoke drift, not wind vanes

2

6–11 km/hr

4–6 knots

Light breeze: wind felt on face, leaves rustle, wind vanes move by wind

Ideal spraying conditions

3

12–19 km/hr

7–10 knots

Gentle breeze: leaves and twigs in constant motion, wind

extends a light flag

4

20–28 km/hr

11–16 knots

Moderate breeze: raises dust and loose paper, small branches move

DO NOT

attempt to apply

pesticides under these conditions

5

29–38 km/hr

17–21 knots

Fresh breeze: small trees sway, crested wavelets form on

inland waters

6

39–49 km/hr

22–27 knots

Strong breeze: large branches move, umbrellas hard to use

7

50–61 km/hr

28–33 knots

Near gale: whole trees move, breaks twigs off trees,

difficulty walking against the wind

8

62–74 km/hr

34–40 knots

Gale: breaks twigs off trees, generally impedes progress

9

75–88 km/hr

41–47 knots

Strong gale: slight structural damage (e.g. chimney pots and roof tiles removed)

10

89–102 km/hr

48–55 knots

Storm: seldom inland, trees uprooted, considerable

structural damage

Reviewed 23 December 2024

Health.vic

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Contact details

Pesticide Safety Program

pesticidesafety@health.vic.gov.au
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