Don’t let the weather impact on campus safety

Met Office applied scientist, Ben Evans looks at the impact of different types of winter precipitation on road surfaces

As the winter months approach, facilities and estates managers on university campuses will undoubtedly be considering their grit and salt requirements for the season ahead. Ensuring the safety of campus users will be paramount, but optimal use of resources can save time and money.

Understanding when it is necessary to grit or salt roads and pathways is not always straight forward, but appreciating the possible effects of different types of winter precipitation on surfaces is one factor which can help ensure that gritting is only carried out when required.

Winter precipitation

The impacts of different types of winter precipitation can vary greatly. Snow is probably the first type to spring to mind, but even the properties of this can vary. Dry snow is relatively uncommon in the UK, but is prone to drifting and occurs when air is cold and dry. Wet snow, however, forms when the air temperature is slightly above freezing, compacts easily on the ground and can therefore lead to icy conditions should temperatures drop further. Fortunately wet snow responds well to salt treatment.

Sleet, as a mixture of rain and snow, does not tend to accumulate on road surfaces, but does have a cooling effect on the surface temperature making ice formation possible. The crushing of hail on road and footpath surfaces by traffic and people can also cause dangerous ice to form.

The most dangerous type of winter precipitation is freezing rain, but this occurs relatively rarely in the UK. The ‘super-cooled’ rain droplets, formed by snow passing through layers of warm and cold air, can freeze instantly into a layer of ice if they fall onto already frozen surfaces. This occurs even if salt has already been put down, causing dangerous conditions for those travelling across the area.

Finally, snow pellets and snow grains, known as ‘small hail’, can lead to ice formation in the right conditions, but usually cause tarmac surfaces to have a white, snowy appearance for only a short time.

Site-specific forecasts

At the Met Office, our science expertise and long-term experience in the road industry has allowed us to develop forecasting services which benefit not only highways’ gritters but also organisations requiring winter gritting for specific sites. Our road surface temperature, rain and snow forecasts play an important part in determining when gritting or salting are necessary, as simple air temperature forecasts are not an accurate indicator. Icy weather causes dangers to both drivers and pedestrians. Gritting campus roads, car parks and pathways when road surface temperatures could cause freezing will help keep campus users safe. Time and resources can also be saved by not gritting unnecessarily, reducing operational expenditure and minimising environmental damage from the over-use of grit and salt.

Forecasts to benefit your campus

Whether you use a winter gritting service or treat the campus yourselves, our site-specific forecasts will save valuable resources. The depth of information within our OpenSite forecasting service ensures that you can be confident in your decision making. Our Quality Mark scheme also provides you with confidence in the forecast accuracy and meteorological training undertaken if using an external winter gritting service.

You can find out more about winter precipitation in the first in our series of new videos, and you may also be interested in our video on road surface temperatures. Visit our website to see the videos and for more information on Met Office winter gritting forecast services

Contact us at

Follow us on Twitter, @MetOfficeB2B, and LinkedIn

Send an Invite...

Would you like to share this event with your friends and colleagues?


We need to talk data governance

Wednesday, June 16, 2PM (BST)