Chilly night, with 3C in Birmingham, as the first frosts approach

Birmingham is in for its chilliest night for some time tonight, as the showers and strong winds of Saturday ease and the skies clear.

The Met Office expects a settled night, with clear spells and a light breeze allowing temperatures to fall into single figures, with a minimum of 3C. Frost is possible in more prone spots further north.

Sunday will start chilly, but sunny spells and a light breeze will make it feel warmer than Saturday. It should stay dry during the day, with a top temperature of 15C, before rain arrives overnight.

Why clear nights are colder

Clouds act like a blanket, trapping heat near the ground. When the sky clears and the wind drops, the heat stored in the ground during the day escapes into space, and temperatures can fall quickly after sunset. That is why the coldest autumn nights usually follow calm, clear evenings.

Ground frost and air frost

The Met Office uses two terms. An air frost happens when the temperature of the air, measured about 1.25 metres above the ground, falls below 0C. A ground frost happens when the temperature of the ground or grass surface falls below 0C, which can happen even when the air is a few degrees warmer. On a night with a low of 3C, a ground frost is possible on lawns and car roofs in sheltered spots, especially on the edges of the city.

Protecting plants

• Move tender plants in pots, such as geraniums, fuchsias and citrus, into a greenhouse, porch or shed, or close to the house wall.
• Cover vulnerable plants in the ground with garden fleece overnight.
• Harvest the last tender vegetables, such as courgettes, beans and tomatoes, before the first proper frost.
• Water plants in the morning rather than the evening, so they are not sitting wet overnight.

On the road

On frosty mornings, allow time to clear every window completely before setting off. Driving with only a small patch of windscreen cleared is dangerous and can lead to a fine. Do not pour boiling water on a windscreen, as it can crack the glass; use a scraper and de-icer instead.

Keeping warm

The NHS advises heating the rooms you use most to at least 18C, especially for older people, babies and anyone with a long-term health condition. It is a good time to check that heating works, to bleed radiators, and to look in on older relatives and neighbours as the nights get colder.

The week ahead

The cold night is a brief interlude. The Met Office expects rain on Monday and a wet, windy morning on Tuesday, but with unusually mild air, before brighter and breezier weather on Wednesday.

City and suburbs

The city centre usually stays a degree or two warmer than the suburbs on clear nights, because buildings and roads release heat stored during the day. Frost is therefore more likely on the edges of Birmingham, in low-lying spots and in open places such as parks and playing fields than in the middle of town.