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Yes, there will always be thunder after you see lightning. It all depends on how close you are to the lightning strike.
Thunder is the result of lightning heating up the air to as hot as 50,000 degrees. This sudden heating of the air causes it to rapidly expand and vibrate the air around it. It is a shock wave that expands away from the lightning stroke.
This wave is the thunder you hear. It may sound like a fire cracker if you are really close to the lightning strike, or it may rumble if you are farther away. This rumble sound is caused by the sound waves reflecting and echoing off the mountains, buildings, canyons and trees. Depending on the wind direction, temperature and other factors, you may hear thunder for up to 15 miles.
Thunder travels at the speed of sound. Remember that the speed of sound is different as the density of air changes. So, the speed of sound changes the higher up in elevation you are and as the temperature changes.
If you see lightning and count to five, the bolt is about one mile away. You can become your own forecaster when you are camping or recreating by simply listening to whether the thunder is getting closer or farther away. Counting to 20 means the lightning strike was four miles away. Counting to 10 means it is two miles away and the storm is getting dangerously close.
I have a rule of thumb about thunder and lightning. "When you count to 10, it is time to come in". Lightning is Utah's number one weather related killer. Thunder is a reminder that there has been lightning somewhere close by. When you see lightning and then hear thunder soon after, you should always go inside a sturdy building until it is safe to return outside.
