How hot is a hot bed?

Now I've made the hot bed - a la Monty Donn- and am ready to plant sweet potatoes and Melons. the spuds down below and the melons up on a hill.
Trouble is My wife says it may spontaneously conbust :roll:
So I have been doing 24 hour max-min thermometer tests and I have found a range from 16 to 44 C!! :!:
 :shock: I must say I was very shocked ........ was expecting a max of about 30 maybe.
I have checked the thermometer at home in tap water and it seems to be working OK.
How can I convince her that the plot is not going to go up in flames?

I have only used Hot Beds in winter and spring so I do not know a lot about summer use,but at this rate you will not be growing Sweet Potatoes you will Growing Baked Potatoes instead  :shock:

  i'll have to check the thermometer again. which would be worse, baked potatoes or my wife being proved right :?:

that black teram will heat it up jim when the sun is on it,try folding the sides up a bit,i think you should be looking at around 30c,

  I'll do that in the morning Shaun and let you know

What's teram?  I was wondering if I could use my big rubble sack, full of fresh manure, as a hot bed next year. Is Monty Don's idea on a website somewhere?

Hi Jeanieblue,
Its nice to be able advise someone at last
All it was, Monty showed us adding layers of horse poo, grass cuttings  etc.......... forking em over to a height of 2 feet .or so.....and covering with about 1 foot of soil/compost.
I covered the lot with black Teram (Shaun had told me about ........ it is woven plastic that allows rain through) ---
And that's yer hot bed
Good luck, Jim