Hi Jeannie
I was there in early June,and visited several places on the lake,stayed at Gardone.Tee shirt and shorts were fine during the day,Some evenings were cooler,requiring a cardigan or light jacket.No mosquitos anywhere,wildlife was fine apart from a stroppy duck which had a tantrum,and left a calling card,when it was not fed,in Salo,a bit south of Maderno.
The hotel supplied discount cards,on request,for reductions on the ferries and some entrance fees.I think that hotels in Maderno did the same.
Keith