We have had a fantastic hot weather spell here in Brittany, but it got to 40 degrees and over in the polytunnel on many an afternoon. My plants have suffered a little but are still cropping well and no sign of blight or other pest and diseases. it just goes to show how much heat tomato plants can take.
I have had a good de-leafing session today as the weather is changing, so I want to give my plants as much air circulation as posible to help prevent blight. It is very important to keep your polytunnel well ventilated at this time of the year with early morning dew about.
My irrigation system has been great, I just put the watering on a time-clock a few times a day and only water with a can when I am feeding the plants.
If the weather cools down and I keep feeding my plants I can keep training them over the wires for another month, then I will nip out the heads of the plants to encourage the last fruits to swell and ripen.