Signs of spring or maybe summer?

There's plenty of cuckoo flower flowering, but no sounds of cuckoos yet; we did get excited to see at least 3 swallows flying with house martins along by the river on our local walk - I know "one swallow does not a summer make" but it's getting closer!
Apparently the saying is "one swallow does not a spring make, nor one fine day; similarly one day or brief time of happiness does not make a person entirely happy" which is attributed to Ariostotle.