Summery, temperate (5)
I believe the answer is:
balmy
I believe this clue is a double definition.
'summery' is the first definition.
(I've seen this before)
'temperate' is the second definition.
(synonyms)
(Other definitions for balmy that I've seen before include "(Of weather) pleasantly warm" , "Of weather, mild and clement" , "Pleasantly mild" , "Warm, summery" , "Mild and pleasant" .)