Plants, especially if in containers or needed for cropping, need nutrients in wet weather. Blight spores use rain to germinate on plants ( the spore pierces the plant surface). A healthy plants can withstand the fungal infections a bit better. Seaweed feed is a real boost for soggy plants. Don't be tempted to concentrate feeds!!!
Soil organisms work at breaking down nutrients in the soil so your plants can absorb them so keep your soil 'sweet'. Standing water in pots and saturated soil stagnates (ask our Somerset gardeners!). Selenium can help 'balance' soil, mycorrhizal fungi, milk and a glass of brown ale works wonders too. Party time for micro organisms.
A canopy (20 quid from IKEA) or an open ended cloche can only reduce blight casualties from rain splashed plants but soil health is key. Feed em!