The only free and comprehensive online etymological dictionary of the Spanish language
verano m. (Noun) "summer"
11th cent. From Vulgar Latin tempus veranum "spring season." The ancient Latins did not sharply distinguish the spring and summer seasons as we do today and in Old Spanish verano meant spring and estío summer until after the Golden Age. For the etymology of tempus, see tiempo. Veranum comes from Latin ver "spring." From Proto-Italic *wes- 'id.' From Proto-Indo-European *u̯es-r/n- 'id.'
Also the origin of the surname Verano.
Indo-European
Romance
Asturian veranu, Portuguese verão, Galician verán, Aromanian vearã, Romanian vară
Celtic
Middle Irish errach "spring," Old Welsh guiannuin 'id.,' Old Cornish guaintoin 'id.'
Germanic
Old Norse vár "spring," Old Frisian wars 'id.'
Balto-Slavic
Old Church Slavonic vesna "spring," Russian vesná 'id.,' Czech vesna 'id.,' Polish wiosna 'id.,' Slovene vẹ̑sna 'id.,' Lithuanian vãsara "summer," Latvian vasara 'id.'
Hellenic
Ancient Greek ἔαρ (héar) "spring"
Armenian
Armenian garown "spring"
Indo-Iranian
Sanskrit vasantá- "spring," Avestan vaŋri "in spring"