Cucumber can get sunburned from intense sunlight, especially when coupled with high temperatures and not having enough water. Afternoon sun tends to be most likely to burn plants. Scalded leaves develop faded patches of light brown to white on the areas at the top of the plant that are exposed to the most sun. They are especially vulnerable to this right after being transplanted from a shadier location to being in full sun. Transitioning plants gradually or providing them with a barrier while they are adjusting can help prevent sunscald in young plants.
In many cases,
Cucumber develops leaves that are large enough to protect fruits from the strongest rays of the sun. However, if intense sunlight is in contact with fruits, they can also be damaged. Avoid over-pruning those protective leaves so that the fruits don’t get burned.