Weather wise, definitely summer! It's cooling and refreshing being out there on a hot summer night, so give me heat and sweat, oh yes, yes!
As for the mozzies, jjj gave me a great tip which worked a treat for me last summer: observe with a fan and blast them away
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Constellation wise, right now is my favourite time of year because I get to see Scorpius and Sagittarius etc, the Southern Cross, and later in the night the the most beautiful story book in the sky of Taurus, Pleiades, Orion etc. Two seasons in one night, wow!