June because it's my birthday month and it's the month with the longest day. I love it when it's bright out until 9 or so in the evening, it makes me feel like I have so much more free time after work. It makes me want to be outside more as I think "it's still early". Whereas in the winter it could be 7pm and I won't go out as it feels much later than it is.
I do like the cooler weather in spring and autumn though, and being able to wear cosy slippers and drink hot drinks at night.