It depends on what is going on with the lava.
In 2003 when we viewed the lava, we hiked for almost over an hour across the lava fields, starting from the end of Craters road in Volcano National Park. With that hike you could get up close and personal with the lava. I got to within about 50 feet - close enough that I didn't want to get any closer because of the heat.
This year when we were there in August, the active lava flow had shifted far to the east, so the viewing access was at a site outside the park, set up by the County of Hawaii at the end of the road that comes from Puna. At that area you couldn't hike to the lave; instead the viewing area was about a 15-minute hike from the parking area.
The county viewing area closes at 10 pm. So it's likely that you wouldn't have enough time to see lava that night. And that's assuming that there is lava to see - when we were there the lava had gone into a tube and was no longer visible at all.
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If yoiu do have time to get to the county viewing area, there are vendors there selling flashlights, ponchos, water, etc. Of course it's more expensive to buy from them, but if you're in a hurry you can get supplied. Flashlights are absolutely essential.