Having only just got my lean to greenhouse I am not sure about what temperature it should be. For instance, before I opened any window and door this morning in full sun it was showing 40oC. I have salad, peas, b beans, spuds, beetroot etc growing. The greenhouse is south facing. I open the roof vent and door and it gets down to around 25 oC but as soon as the cloud comes the temp drops so I have to be careful.