Incubator Temperature for Chicken Eggs: Getting It Right
TL;DR: 99.5°F (37.5°C) forced-air, 100–101°F (37.8–38.3°C) still-air. The setting is the easy part. What decides your hatch is where you measure — at the top of the eggs, not on the floor — and whether your thermometer is telling the truth, which you check with a second one before setting eggs. Running hot damages a batch faster than running cold. In a brownout, keep the lid shut and insulate; do not open to look.
The full 21-day process is in our how to incubate chicken eggs guide. This one goes deeper on the single setting that ruins the most hatches.
The Numbers
| Incubator type | Target | Why |
|---|---|---|
| Forced-air (has a fan) | 99.5°F / 37.5°C | Air is mixed, so temperature is near-uniform throughout |
| Still-air (no fan) | 100–101°F / 37.8–38.3°C, measured at the top of the eggs | Warm air rises, so the cabinet is layered; the higher target compensates |
Applying the still-air figure to a forced-air machine runs it dangerously hot. Know which machine you have before you set anything.
Where You Measure Decides Everything
The temperature that matters is the temperature at the embryos, which means at the level of the top of the eggs.
- Not on the floor of the incubator, which reads cooler in a still-air unit.
- Not near the heating element, which reads hotter.
- Not against the wall, which is affected by room temperature.
In a still-air incubator this is not a refinement, it is the whole measurement. The difference between floor level and egg-top level in a layered cabinet is large enough to decide whether your batch hatches.
Verify the Thermometer Before You Trust It
This is the step that separates keepers who get consistent hatches from keepers who do not.
A built-in display reads one sensor in one position, and sensors drift. A display showing 37.5°C while the eggs actually sit at 38.5°C is invisible — everything looks correct and the hatch fails anyway.
Before setting eggs:
- Run the incubator empty for at least 24 hours at the target setting, with the water channels filled as you intend to run them.
- Put a separate thermometer at egg-top level and compare it to the display.
- If they disagree, trust the separate thermometer and adjust the machine so the reading at egg level is right — the display number becomes just a reference point.
- Check more than one spot in the tray. Cheap machines have cool corners; a spot that runs consistently cool is a spot you rotate eggs through rather than leave them in.
- Watch the swing over a few hours. A machine that cycles between 36.5 and 38.5 averages fine and is still a bad incubator.
Do this once, properly, and every future hatch benefits.
What Going Wrong Looks Like
| Running | Effect on the batch |
|---|---|
| Too hot | Faster development, early hatch (day 19–20), higher rate of weak, deformed and poorly absorbed chicks. Damage accumulates quickly |
| Too cold | Slower development, late and drawn-out hatch (day 22+), weaker chicks, fewer hatching at all |
| Swinging | Uneven development, a hatch spread over several days, mixed results |
Hot is worse than cold. A cool spell delays; a hot spell kills. If you are unsure and cannot verify, erring very slightly cool is the safer error.
Our why eggs did not hatch guide covers how to read a failed hatch backwards, and the timing of the hatch itself is one of the most useful clues about temperature.
Brownouts: The Philippine Problem
Power interruptions are a normal part of running an incubator here, and panic does more damage than the outage.
What to do:
- Keep the incubator closed. Every opening loses accumulated heat and humidity.
- Insulate it — a blanket or towels over the unit, keeping vents from being fully blocked.
- Move it somewhere warmer if part of your house is warmer, without opening it.
- Do not open it to check the thermometer. You know what the reading is: falling.
- When power returns, let it come back up on its own. Do not overshoot the setting to “catch up” — that is how a survivable outage becomes a cooked batch.
- Record it. Note the date and duration. Expect the hatch to run late by roughly the time lost.
Eggs have thermal mass and cool slowly, and a broody hen leaves the nest daily without ruining her clutch. Short outages are frequently survivable. Long ones may not be, and the honest answer is you will find out at candling — see candling eggs.
If outages are routine where you are, the most reliable incubator on the property may be a broody hen — see hatching under a broody hen.
Ambient Conditions Matter More Than You Expect
Cheap incubators heat but do not cool. In a room that gets hot in the afternoon, the machine cannot bring the temperature back down.
- Put the incubator in the most temperature-stable room you have — interior, out of direct sun, away from windows and doorways.
- Not near an electric fan pointed at it, and not in a draught.
- Not on the floor if the floor is cold, and not against a hot wall.
- Check it at the hottest part of the day, not only in the morning. A machine that holds 37.5 at 7am and 39 at 2pm is the problem.
The Honest Limits Here
The temperature ranges given here are standard, long-documented incubation figures that hold across brands and chicken types, and they match our main incubation guide. What this guide cannot do is tell you how your machine behaves: every unit has its own hot and cool spots and its own drift, and the only way to know yours is to verify it with a separate thermometer and track results across hatches. Always follow your incubator’s own manual where it gives a specific instruction for that model.
Related: incubator humidity, egg turning, lockdown at day 18, how to incubate chicken eggs.
Frequently Asked Questions
What temperature should an incubator be for chicken eggs?
About 99.5°F (37.5°C) for a forced-air incubator with a circulating fan, or 100-101°F (37.8-38.3°C) for a still-air incubator without one. The higher still-air figure accounts for the temperature layering inside a cabinet with no air movement.
Why do still-air and forced-air incubators need different settings?
A forced-air unit mixes the air so the temperature is nearly the same everywhere. A still-air unit is warmer near the top and cooler near the floor, so the reading is taken at the top of the eggs and the target is set higher to compensate.
Where should the thermometer sit?
At the level of the top of the eggs, where the embryos actually are — not on the floor of the incubator and not up against the heating element. In a still-air unit this placement is critical rather than merely helpful.
What happens if the incubator runs too hot?
Development speeds up, hatch comes early, and chicks are more likely to be weak, poorly absorbed or deformed. High temperature does more damage faster than low temperature does.
What happens if it runs too cold?
Development slows, hatch is late and drawn out, and chicks may be weak. A prolonged cold spell reduces the number that hatch at all.
What do I do during a power outage?
Keep the incubator closed, insulate it with a blanket, and do not open it to check. Eggs cool slowly and short outages are often survivable. Note the outage in your records and expect the hatch to run slightly late.
Should I trust the incubators built-in display?
Verify it against a separate thermometer before you set eggs. Built-in sensors sit in one spot and are not always accurate, and a display reading 37.5 while the eggs sit at 38.5 is the most common invisible cause of a bad hatch.