You can estimate how far the lightning is from you by timing the gap between the flash and the thunder and doing a quick calculation.

Quick method (rule of thumb)

  1. When you see the lightning flash, start counting “one‑thousand‑one, one‑thousand‑two…” until you hear the thunder.
  2. Take the number of seconds you counted and:
    • Divide by 5 to get distance in miles.
 * Divide by 3 to get distance in kilometers.

Examples:

  • 5 seconds between flash and thunder ≈ 1 mile (about 1.6–1.7 km) away.
  • 10 seconds ≈ 2 miles (about 3.2–3.3 km) away.
  • 15 seconds ≈ 3 miles (about 5 km) away.

This works because light reaches you almost instantly, but sound travels much slower (roughly 1 mile in 5 seconds or 1 km in 3 seconds).

Simple HTML table for quick reference

html

<table>
  <thead>
    <tr>
      <th>Seconds between flash and thunder</th>
      <th>Approx. distance (miles)</th>
      <th>Approx. distance (km)</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>5</td>
      <td>1</td>
      <td>1.6–1.7</td>
    </tr>
    <tr>
      <td>10</td>
      <td>2</td>
      <td>3.2–3.3</td>
    </tr>
    <tr>
      <td>15</td>
      <td>3</td>
      <td>5</td>
    </tr>
  </tbody>
</table>

Safety note

  • If the time is very short (just 1–3 seconds), the lightning is extremely close and you should move indoors immediately.
  • Weather agencies say that if you can hear thunder at all, you are close enough to be struck, so the safest move is: “When thunder roars, go indoors.”

You can’t get an exact live distance from me without a specialized sensor, but using the counting method above will give you a solid estimate of how far the lightning is from you right now.

TL;DR: Count the seconds from flash to thunder, divide by 5 for miles or 3 for km; if the number is small, get inside and stay there until 30 minutes after the last thunder.

Information gathered from public forums or data available on the internet and portrayed here.