Pretty much Margoo. We have a lovely big area we are allowed to let the dogs run in (pony club X country grounds). Tracks, bush, rabbits, dam etc etc. But we don't go near it in summer - much to the dog's disappointment!! They drag off towards the gate every time we walk past but I just wouldn't risk it. We do have a fenced oval where they can run which is just mown grass and safer.
Really early morning might be ok, so long as it's not warming up a little and they're out to catch some early rays!