One of the following is not an early sign of heat illness: confusion.

Early Signs of Heat Illness

• Heavy sweating
• Cool, moist skin (sometimes with goose bumps)
• Dizziness or faintness
• Fatigue or weakness
• Headache
• Nausea
• Muscle cramps
• Fast heartbeat or pulse

Signs that Are Not Early But More Severe

• Confusion
• Slurred speech
• Seizures
• Coma

Confusion, slurred speech, seizures, and coma are signs of severe heat illness such as heatstroke, which occurs later and is a medical emergency rather than an early sign.