Two weeks ago the local allotment had their annual plant sale. They said the
beans and tomatoes were not good and they had none for sale and to come back
in two weeks. Yesterday on visiting again they had hardly any on display.

They said the problem was the weather being so hot, that the poly tunnels
got too hot, and opening up the tunnels at each end was not enough to solve
the problem.

What struck me was, that if you covered the tunnels with old blankets or
rugs or something similar, would that not cool the tunnel down? Since it's
the effect of the transparent plastic that is responsible for a lot of the
heating effect, i would have thought?