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Is my hay hot enough to catch fire?
Wet hay heats up on its own and can burst into flame weeks after baling. Enter your probe reading and see what to do.
| Temp | What it means · what to do |
|---|---|
| Under 125°F | Normal curing. No action needed. Keep checking for the first six weeks. |
| 125–149°F | Warm, and mold can grow. Check twice a day and watch which way it's heading. |
| 150–159°F | Entering the danger zone. Check twice a day. Take stacks apart so air can cool the hay, and move it outside if you can. |
| 160–174°F | Danger zone. Check every couple of hours. From here on, only unstack with the fire department there. |
| 175–189°F | Hot spots or fire pockets are likely. Call the fire department now. Close the barn up tight to cut off air. |
| 190°F and up | Fire is likely. Remove hot hay only with the fire department there. Bales can burst into flames the moment they hit fresh air. |
Taking a reading
Use a hay probe thermometer. Or drive a sharpened pipe into the stack and lower a thermometer down it on a string.
Wait 10 to 15 minutes, then pull it up and read it fast. Check the middle of the stack, where heat builds.
When to worry
Most hay fires happen in the first six weeks after baling.
Check new hay twice a day until the temperature holds steady.
Bale it dry
A common guide for safe baling moisture:
- Small squares: under 20%
- Large rounds: under 18%
- Large squares: under 16%
Wetter than that? Use a preservative, or let it dry longer.
Where I come in
Hay dust on a hot light, a chewed wire or a loose connection can start a barn fire too.
A heat-camera scan finds hot spots before they start one. See the barn inspection →
Temperature steps are adapted from Ohio State University Extension's hay fire chart. This is general guidance. In an emergency, follow your fire department.