Frost

[MojoJojo]

Ok, real newbie question here...

Since I've started growing stuff/planning to grow stuff, I've started paying more attention to weather, and particular the frost.

According to the forecast, haven't had a frost (i.e. 0C or less) for at least a week. But at 3am on Wednesday, when the baby woke me up and there was a full moon, I looked out the window, and I'm pretty sure the water on the flat roof looked iced up. It was 3am. In the morning I didn't see any obvious sign of frost.

This has sparked memories of weather forecasters talking about "ground frosts" and things, which somehow happened above 0C... and I don't know.

Basically, what sort of minimum temperature should I be running out to pull things in pots inside and throwing fleeces over everything?

[Potstubsdustbins]

Yup you don't need to go down to 0` to get a frost. It really does depend on what you have out side as to when you start to worry.

Let us know what you have and we maybe able to advise.

Colin

[Nicos]

Rule of thumb is start worrying at 4C ( have you noticed that's when the car's frost warning sign comes on too????)

If you are in a frost pocket then the local forecast won't be accurate enough to go by.
Our exposed veg garden is at least 5C cooler than our neighbours sheltered garden and our hamlet can be about 8C cooler than the local village. Weird eh????...it just depends on wind direction ( or not) and cloud cover.
We tend to be hotter in the summer.

So basically what I'm saying is that if you pay careful attention to your local weather forecast then you'll get a feel for the slight variation with your veg plot/garden.

Incidentally we had -7C on Wednesday morning! and yup that was the first night my broad beans were over nighting in the blowaway! Typical or what? Forecast predicted -1C but it was cloudy when we went to bed!

Have a pile of fleeces to hand and nip out and chuck them over young plants if you're worried- and if you were wrong- then hey, it's better than loosing carefully nurtured plants!

[Two_Sheds]

at 3am ... there was a full moon

Just before dawn is the coldest part of the night: any warmth left in the ground from daytime has gone. Add in a clear night and it's going to be even colder (clouds are like duvets, trapping warmth to the earth)

Your last frost is due in early May ~ that's for Cambridge as a whole. As Nicos said, your own garden may vary slightly. First and last frost dates for towns and cities in the UK and USA

[MojoJojo]

Thanks for the answers - and the last frost dates is useful!
I should get some fleece soon!
Just planted potatoes and spinach is just starting to peek above the ground. Only other things outside are garlic and rhubarb, and they've been out all winter!

Anyway I found this link which gives a bit more information on the difference between an air frost and a ground frost - What's the difference between a ground frost and an air frost? | Weather FAQs

[Peas'n'Kews]

Remember that the weather mannie on the telly is quoting temperatures at head height - so it can be much colder at soil level...

(I fear "head height" may induce some comments, I am a shortie!!!)

[Aberdeenplotter]

pssst, don't throw over fleece, throw over some straw