Fog typically occurs most in cold weather or when temperatures cool noticeably (such as the period entering autumn from summer). It can have a significant impact on visibility, as can stormy weather.
Travelling in fog
The below is all advice from the Met Office:
Give yourself the best chance of avoiding delays by checking road conditions if driving, leaving extra journey time, or amending plans if necessary.
Make sure you know how to switch on your fog lights, and check they are working before setting off on your journey.
Bus and train services, as well as flights and ferry travel may also be affected; check for updates from your travel company and follow their advice
Further advice for road users
- Make sure you know where your fog light switch is before you set off.
- Keep a bigger distance between you and the car in front.
- Be prepared for a sudden bank of fog or drifting, patchy fog.
- Check your mirrors and slow down before entering fog.
- Use fog lights when visibility drops below 100 metres, which is roughly the length of a football pitch.
- Don't use full beam as fog reflects the light back.
- Once the fog has lifted, switch off your fog lights.
Levels of fog and visibility impact
The Met Office will indicate that there is fog when visibility is at 1000m or under. However, there are differing levels of fog, which are based on visibility range:
- Under 1000m - known as 'aviation fog'. Only air travel is likely to be affected.
- Under 200m - considered to be 'thick fog'. This is typically impactful to everyday travel.
- Under 100m - according to the Highway Code, any vehicle on the road must use fog lights.
- Under 50m - considered 'dense fog'. This is likely to cause severe disruption.
The lower the visibility, the more likely it is that travel will be affected. Fog can lead to cancelled flights or public transport.
The Met Office may issue a weather warning depending on the likelihood and severity of fog, with a red warning being the most severe.
Advice in moderate or severe fog conditions
The general recommendation is to avoid travelling in fog where possible. This is especially true when the fog is considered dense and visibility is under 50m.
Be prepared for weather warnings to change quickly: when a weather warning is issued, the Met Office recommends staying up to date with the weather forecast in your area.
If you have travel plans, make sure to regularly check schedules (such as flight times, train times or bus schedules) as they could change. Consider setting off early if travel is necessary.
When crossing roads, be extra careful and consider that other road users will have less time than normal to spot you.