Note that Monthly and Weekly challenges run in June, too.
When? June 1st to June 30th
What? Draw an image based on a pose reference photo picked by senshistock for that day.
Where, how to take part: Watch senshistock on deviantart
2018 announcement - 2018 gallery
When? June 1st to June 30th
What? Draw bugs, ideally one per day
Where, how to take part: Post anywhere using the tag “junebugs”
When? June 1st to June 30th
What? Create details of a world you are creating. Writing or art are welcome; there is a prompts list.
Where, how to take part: worldbuildingjune.tumblr.com
Junefae is a creative challenge running from June 1st to 30th
What's the challenge? Draw fairies or other fae, ideally one per day
Where and how to take part: Post anywhere, using the tag “junefae”.
When? June 1st to 30th
What? Draw kaiju or other monsters, ideally one per day
Where, how to take part: Post anywhere, using the tag “kaijune”.
When? June 1st to 30th
What? Draw unicorns, ideally one per day
Where, how to take part: Post anywhere, using the tag “junicorn”.
This is an art challenge running every year from June 1st to August 31st. You can take part in one, two, or three months.
What? Draw something every day to a topic you chose yourself.
Where, how to take part: Sign up at Livejournal or Dreamwidth. There is a Tumblr, too.