If you're tied to it being night per se to make it scary, many of the other suggestions here will serve you in good stead.
But if you want to make it scary and creepy, there's a general formula:
Make things almost, but not quite, normal.
Sure, darkness is scary because you can't see. But what if you suddenly stopped casting a shadow? Or if you stopped hearing your footsteps, or the background noise around you. 'Quiet' and 'silent' are two different things, especially out in nature! What if you had the sneaking suspicion that rooms were moving around you? What if you saw people, but they made no noise and didn't react to you?
The Uncanny Valley is the principle that things that look almost normal, but not quite, flip a natural switch in peoples' minds. It's like how silly physics in Call Of Duty can be very annoying, but in Halo it's hilarious. When things don't seem remotely normal, one more strange fact wont be terribly upsetting; it's the new normal. But when things are normal, your brain runs through a checklist of your expectations - and notices when something doesn't fit. Which would be creepier and scarier; a six-legged animal with fangs, or a six-year-old girl with fangs?
One of the greatest tools a DM has isn't knowing what's scary - it's knowing what's not. And then nudging just a little. Because that's terrifying.