Don this is from later sowing. I never sow peas here after the first week of April, in cooler regions it will be later. May sowings crop later but are prone to mildew which is prevalent after midsummer. Hence no May sowing in my timeline.
Watering should help but once established it may be difficult to stop and the pea flavour is less sweet, from reduced photosynthesis.
I prefer to sow French beans in May, just starting now and delicious..