Fertialized Eggs RimWorld Outdoors — 0–50°C Safe Range + Hatch Tool (1.6)

Outdoor Hatching Without Heartbreak:
Make Your Fertilized Eggs RimWorld Outdoors Actually Hatch

Keep eggs between 0–50°C, roof them, and don’t refrigerate them. This tool uses Core defs to show hatch time by egg type and how fast “Ruined by temperature” happens when you go out of range.

Safe band: 0–50°C Chicken egg hatch: 3.5 days Data: Core defs 1.6.4633

Tip: Egg boxes reduce hauling churn and protect eggs from outdoor deterioration (but not temperature damage).

Quick Solution Fastest reliable outdoor hatch

Short answer: yes, fertilized eggs can hatch outdoors if temperature stays safe and the eggs don’t lose HP to deterioration.

Roofed egg boxes (or roofed shelf) near your barn.
Stockpile: allow Eggs (fert.) only.
Keep temp: 0°C to 50°C.
Prevent hauling & predators: set priorities and add a door/fence so wildlife doesn’t path through.

Want the exact numbers? Scroll to Game Data.

Safe Range 0°C to 50°C Interactive check

The safe band comes from CompProperties_TemperatureRuinable on EggFertBase (Core defs).

Too Cold Too Hot

Egg type (fert.)

Ambient temperature (°C)

Placement toggles

Roofed (no deterioration) In egg box (also protects outdoors)

Adjust temperature and egg type to see the safe-range check, hatch time, and the temperature-ruin timer.

Hatch time (days)—

Temp status—

Time to “Ruined” (if unsafe)—

Deterioration risk—

Safe Setup Example

Egg box holds up to 25 eggs; pawns only empty it at 20+ (saves hauling time).

Stockpile snippet (recommended):

Stockpile: Hatch Patio (Preferred)
Allow: Eggs (fert.)
Disallow: Eggs (unfert.) + all other foods

Kitchen bills:
Exclude Eggs (fert.)

Links: EggBox (ThingDef) · EggChickenFertilized (ThingDef)

Roof vs. Unroofed Deterioration Don’t let weather eat HP

Unroofed

Major HP loss

Eggs have only 20 Max HP in Core defs. If left unroofed on the ground, they can disappear before hatch day.

Roofed

No HP loss (from deterioration)

A cheap roof (or an egg box) prevents outdoor deterioration. Temperature is still the big threat.

Note: the EggBox description explicitly says it “protects eggs from deteriorating outdoors” but “does not protect from temperature damage”.

Biome Heat Challenges Cause → fix

Problem	Likely cause	Quick fix
Ruined by temperature	>50°C or <0°C	Passive cooler or campfire (temp back into safe band)
Hatch stuck at 0%	Eggs stored below 0°C (freezer)	Move eggs to a warm stockpile (not your freezer)
Eggs vanished	Left unroofed (deterioration)	Build a roof (or use egg boxes)

Temperate

35°C

Rain

35°C

Boreal

~-20°C

Cold

-40°C

Animals Logic: better egg handling overlays.

RimKeeper – Wild Animal Procreation: wild egg tweaks (modded).

Quick Tips: hatch eggs video.

External links: Animals Logic · RimKeeper · Video

Patch History Highlights Why 1.6 matters

Patch	Date	What changed
1.6.4518	Jul 2025	Unfertilized egg defs exist for each egg type; ruined fertilized eggs convert to the unfertilized version (so mistakes become food instead of trash).
1.6.4535	Jul 2025	Stability fixes (less weird hauling churn / logic edge cases).
1.6.4630	Oct 2025	Maintenance patch (no direct egg rule changes).

Game Data (Core defs) 1.6.4633 rev1266

Egg safe temperature and hatch days are pulled from local Core XML defs (paths shown below).

Egg (fert.)	Hatches into	Days to hatch

Show exact source paths

Safe temperature band: /game/Data/Core/Defs/ThingDefs_Items/Items_Resource_AnimalProduct.xml → ThingDef EggFertBase → CompProperties_TemperatureRuinable

Hatch days: /game/Data/Core/Defs/ThingDefs_Items/Items_Resource_AnimalProduct.xml → each ThingDef ParentName="EggFertBase" → CompProperties_Hatcher

Egg box behavior (outdoor deterioration protection, stack limits): /game/Data/Core/Defs/ThingDefs_Buildings/Buildings_Misc.xml → ThingDef EggBox