Autumn sun? FROST TONIGHT!!

[tim]

Wrap up! = Tim

Just checked - 36F in the greenhouse last night.

[tim]

[sandersj89]

Earlier in the week we dipped to 5 degrees centigrade, they are forecasting lows of similar levels tonight.

Wont be long before the bubble wrap goes back into the greenhouse.

Jerry

[Kerry]

pah! bbc weather last night forecast frost for quite a large part of the country.
Having the flat roof re-roofed today, went out with their essential cups of tea and it was quite chilly - very blue sky but a certain nip in the air!
It wasn't that long ago I took the shading off the greenhouse. boohoo!

[Jesse]

Yesterday I noticed that my neighbour's climber on the front of her house has frost damage, strangely that little patch of garden always gets the frost first. So I rushed out and bought some fleece and hopefully the frost will hold off until tomorrow so that I've got time to wrap up all my tender plants.

[Tenuse]

At what temperature do we get frost? Is it dependent on other factors as well?

Ten x

[Mrs Ava]

No idea how cold it has to be to get a frost, but I think sometimes the really cold wind does more damage stripping any moisture from the leaves and burning them to a crisp!  I notice a lot of the trees around daughter number ones school have started to colour up for autumn, especially the Horse Chestnuts!  Fleeced lots of things at the allotment and will start moving tender plants to the house walls this afternoon.  Heater back into the greenhouse tonite I fear, just on the frost free lowest setting, just in case!  Need to get those toms ripe!!  

[aquilegia]

It was freezing when I left home at 8am this morning. My breath was frosting and I wanted to (but didn't have time to) go back and get my woolly hat (new one as well!)

The cars parked along the street had dew on which looked a bit frosted. I noticed the other day the flat roof of a neighbour's garage looked distinctly frosty.

Already? I'm sure we didn't get frost til last October last year.

Oh heck - I've just remembered it's almost October - this year is going so quickly!

[sandersj89]

At what temperature do we get frost? Is it dependent on other factors as well?

Ten x

Frost comes in two sorts, ground frost and air frost. Weather forcasters measure the air temperature in those little white louvred boxes which are called Stevensons screens. They also contain other instruments to measure such things as humidty.

A frost is declared when the air temp in the screen reaches zero degrees celcius. Often at this time of year we get air frosts and the soil stays above freezing dues to risidual heat.

Ground frosts are when the ground reaches zero degrees, the lower the temperature the deeper the frost penetrates into the soil surface. It is possible that the ground temperature reaches zero though the air stays 1 or 2 degrees above. Not sure of the eact science here though.

You can also get into the situation where the ground stays frozen below soil level even when the aire is 4 or 5 degrees. The top layer of soil may thaw but it does not have time with sort days the thaw completly.

Obviously further damange can be done if there is a wind attached to the cold temps. This creates wind chill and sucks moisture out of plants and ground.

One other point, in some cases it is not the freezing that does the damage to some plants, it is the action of direct sun on te plant in the morning while frosted. A rapid thaw damages plant cells.

HTH

Jerry

[Tenuse]

Yikes! So my rather simplistic method of checking the likely lowest night temperature isn't enough then  ;)

Ten x

[tim]

Great spiel, Jerry. Funny, though, that if you get up before the sun & spray the plants, it usually saves them? = Tim