With a cooler northerly flow bringing lower than average temperatures for the time of year and the risk of overnight frost for some, we explore why frost can still occur late into Spring.
As days grow longer and sunshine strengthens, frost is often the last thing people expect. Yet frosts can and do still occur well into late spring, including May.
While these events are usually short‑lived and localised, they can catch gardeners and growers by surprise and help explain why frost may still be referenced in weather forecasts at this time of year.
Understanding how frost forms, and the conditions that favour it, helps explain why cold nights can still develop even as daytime temperatures rise.
What is frost?
Frost forms when temperatures at the ground or in the air fall to or below the freezing point of water. It is possible for frost to occur even when daytime conditions feel mild, particularly under the right overnight conditions.
There are two key types of frost to consider. Air frost occurs when the air temperature falls below freezing, typically measured at around one metre above the ground. Ground frost happens when the temperature at the surface drops below 0°C, even if the air temperature slightly above remains positive.
Gardens and crops are most commonly affected by ground or grass frost, which can damage tender plants despite thermometer readings staying just above freezing.
Clear skies and rapid cooling
One of the most important ingredients for frost is a clear night sky. After sunset, the ground loses heat as it radiates energy back into the atmosphere and out to space. Cloud acts like a blanket, trapping some of this heat and slowing the cooling process.
On clear nights, heat escapes more efficiently, allowing the ground and objects close to the surface to cool quickly. Even during late spring, when days are noticeably warmer, clear skies overnight can still allow temperatures at ground level to fall below freezing.
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Light winds and cold air pooling
Wind plays a key role in determining how cold it becomes overnight. Light winds allow colder, denser air to settle near the ground, forming a shallow layer of cold air where frost can develop. Stronger winds mix the air, drawing in slightly milder air from above and reducing the chance of frost forming at the surface.
This is why frost risk is often highlighted on calm nights, particularly beneath areas of high pressure, which typically bring lighter winds and clearer skies.
Ground cooling and grass frost
In May, ground frost is more common than air frost. At this stage of the year, the ground has not yet accumulated as much stored warmth as it does later in summer. This means that similar air temperatures can lead to colder ground conditions than they would in early autumn.
Different surfaces also cool at different rates. Short grass, soil and vegetation lose heat more quickly than materials such as concrete or roads, which retain warmth for longer. As a result, grass frost can occur even when nearby paved surfaces remain frost‑free.
This type of frost can develop during late spring and even early summer, particularly after a clear and calm night, and is often localised to rural areas.
We've had some frosts this month and there's more pockets likely in the coming nights. This map shows it's not that uncommon to get air frosts late in spring ❄️ pic.twitter.com/KySW3cF22M
— Met Office (@metoffice) May 7, 2026
Why rural areas are more at risk than towns
Frost is more common in rural locations than in urban areas. Open countryside allows heat to escape more freely, while valleys are especially prone as colder air drains downhill and pools near the surface overnight.
By contrast, towns and cities tend to stay slightly warmer. Buildings, roads and other hard surfaces absorb heat during the day and release it slowly at night. This so‑called urban heat island effect reduces the likelihood of frost in built‑up areas compared with surrounding countryside.
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Last frost dates vary widely
Looking at average dates of the last air frost highlights a clear north‑south pattern across the UK. In southern and coastal regions, the average last air frost tends to occur earlier in the spring, often before April comes to an end.
Further north, and over higher ground, the average last frost often extends well into May and, in a few places, even into June. This means that frost at this time of year is not especially unusual, particularly in rural, elevated or sheltered locations.
Frost and a warming climate
Comparing more recent climate averages with earlier periods shows that the average date of the last spring frost has been shifting earlier in the year. This is consistent with a warming climate.
However, this does not remove the risk of late frosts altogether. In fact, they can become more problematic for gardeners and growers. Warmer springs can encourage plants and blossoms to develop earlier, leaving them more vulnerable if a late cold snap does occur.
Why frost is still important in forecasts in May
Although widespread frosts become less common as spring progresses, the conditions needed for frost can still develop. Clear skies, light winds and dry air under high pressure can combine to produce sharp overnight temperature drops, even when daytime conditions feel mild.
References to frost in weather forecasts at this time of year are designed to highlight these risks, particularly where sensitive plants, crops and blossom could be affected. Paying attention to forecast guidance helps manage the final cold snaps before more settled warmth becomes established.
Keep up to date with weather warnings, and you can find the latest forecast on our website, on YouTube, by following us on X and Facebook, as well as on our mobile app which is available for iPhone from the App store and for Android from the Google Play store.
