Data
Understanding the UV Index
The UV Index measures the intensity of ultraviolet radiation from the sun. Developed by the World Health Organization, it helps you understand when sun protection is needed. In Ottawa, the UV index typically ranges from 0–2 in winter to 7–10 in summer.
☀️ Factors Affecting UV
- • Time of day: Peak at solar noon (11 AM – 3 PM)
- • Season: Highest in June–July around summer solstice
- • Cloud cover: Clouds reduce but don't block UV
- • Altitude: UV increases 10–12% per 1,000m elevation
- • Reflection: Snow reflects up to 80% of UV rays
🛡️ Sun Protection Tips
- • Apply SPF 30+ sunscreen 15 minutes before going outside
- • Reapply every 2 hours and after swimming or sweating
- • Wear a wide-brimmed hat and UV-blocking sunglasses
- • Seek shade during peak UV hours (11 AM – 3 PM)
- • Cover up with long sleeves and pants when UV is high
Ottawa UV Index by Season
Winter
UV 1–3
Low risk. Snow reflection can increase exposure.
Spring
UV 4–6
Moderate. Sunscreen recommended outdoors.
Summer
UV 7–10
High to Very High. Full protection needed.
Fall
UV 2–5
Low to Moderate. Protection on sunny days.
Data source: Open-Meteo Weather API
UV index data is updated hourly. The UV index scale was developed by the World Health Organization and Environment Canada to help Canadians protect themselves from overexposure to the sun.