Toddler nightmares may stem from listening to a story that’s scary (even if it doesn’t seem scary to you), watching an upsetting program or movie, getting excited or worked up before bed, or feeling anxious or stressed during the day.
Get into a healthy sleep routine. Try to go to bed about the same time and wake up at the same time every day. …
Sleep with a stuffed toy or favorite blanket. This helps some kids feel more secure.
Use a nightlight. …
Keep your door open.
Reassure your child that you’re there. Your calm presence helps your child feel safe and protected after waking up feeling afraid. …
Label what’s happened. …
Offer comfort. …
Do your magic. …
Mood lighting. …
Help your child go back to sleep. …
Be a good listener.

Night lights really help!!!! In this weather he may also be thirty and/or wanting comfort. My 19 month old has only just started sleeping through the night. Otherwise comfort and reassurance.