We had glorious weather on Canna where I found this sign. There has been a lot of noise nationally from the opponents of solar power about how their performance is poor in hot weather. I looked it up here. It seems that, yes, there is a slight reduction in power output but from the figure quoted, it is not a pronounced effect. On Canna, anything over 25 Celsius would be amazing - though perhaps the panels themselves reach a higher temperature because they are dark and absorb.
