Vine crops like cucumbers are heavy water feeders, so you should constantly check soil moisture daily in this unusually hot weather. Cucumbers need about one inch of water from rainfall or irrigation each week during the growing season. Terraced cucumbers need extra water.

Newly transplanted cucumbers may not have grown a large enough root system to compensate for water loss or nutrient deficiency. Nutrient deficiency in seedlings is a common problem in early spring. Their immature root unable to uptake nutrients that are held in soil organic matter. Cool soil temperatures inhibit soil microorganism activity and processes that allow nutrients to be released and made available to plant roots.  A little earlier this spring, cucumber froze in some areas of the state. This could cause you soil to still be cool.Leaves may yellow and die if sufficient nutrients are not available to plant roots. Nitrogen may be in short supply early in the growing season. Iron chlorosis is a yellowing of plant leaves while the tissue close to the leaf veins remains green. Typically, it is caused by an iron deficiency, usually due to a high soil pH (pH above 7.0). It is normal for seed leaves called cotyledons often turn yellow.
Please send us a picture of the plants if you have more questions.