By definition, all thunderstorms produce lightning. If you can hear thunder you are close enough to the storm to be struck by lightning and therefore should move inside. Remember that it doesn't have to be raining for lightning to strike. Lightning can strike 10 to 15 miles away from the rain because lightning strokes come out of the upper portions of the thunderstorm cloud that extends 5 to 10 miles into the atmosphere.
Lightning travels the easiest route, from the cloud to ground, often striking the tallest object.
Therefore, try not to make yourself the tallest object or stand near the tallest object in your immediate vicinity. If you're outside, you should not stand in an open field, on a beach or hilltop, under an isolated or large tree, or near a pole, and do not stay on a boat or near water. If you are in a wooded area you should seek shelter in a low area under a thick growth of small trees. If you are with a group of people, spread out and keep several yards apart from each other. Stay away from metal objects such as fences, poles, and equipment.