I know it's only 4 years away .... but what the heck.
Closest approach is at 0751 UT on July 31, 2018. Opposition is on July 27, 2018.
There's not too much of a trade-off between seasonal variation in elevation vs. time-of-night around July-August 2018, but each observer should still figure out what's best for their viewing location with regard to local conditions.
Apparent Diameter shrinks either side of the 27-31 July period fairly quickly, losing roughly around 15% within 30 days either side, so mid-July to mid-August is the period to aim for - it will be a maximum of 24.3" during this apparition.
Declination at the peak period will be approximately -25.8 deg (South), meaning bloody good viewing from the Southern Hemisphere.
For example (according to Stellarium, so take this with a pinch of salt), from
Brisbane (27.5 deg South):
- On 27 July, during Opposition, Mars will rise to a maximum elevation of 88.1 deg at 23:59, but the moon (99.9%) is only 7 degrees away at the same time.
- On July 31, during closest approach, Mars will rise to a maximum of 88.4 deg above the Northern horizon at 23:39. There's still a moon (93%) in the sky around then, but it's about 45 deg away at that time.
- On August 4, Mars will rise to a maximum of 88.7 deg, at 23:18 with moonrise (60%) occuring around half an hour later (23:52).