What is the Nagano UV index scale today?
Consult the Nagano UV index today to determine whether sun exposure is safe or if precautions should be taken.
The current Nagano UV index is low, registering at 2.619. Enjoy outdoor activities safely, as the sun's rays are not very strong.
2026-09-09 05:56 UTC
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What's the UV right now in other cities of Japan (today's UV rays)
Nagano Real-Time UV Index Forecast Chart (Hourly Nagano UV Index Chart)
Explore the Nagano UV index forecast chart for the coming hours to stay informed about the varying levels of ultraviolet radiation throughout the day.
Safe Exposure Time Calculation (Time to Burn Chart)
The most commonly used scheme to classify a person's skin type by their response to sun exposure — the degree of burning and tanning — was developed by Thomas B. Fitzpatrick, MD, PhD. As a matter of fact, even the skin colours of Emoji characters are based on the Fitzpatrick scale.
| Skin Type | Color | Typical Features | Tanning Ability | Time to Burn (minutes) |
|---|---|---|---|---|
| I | Red or blond hair; light-colored eyes; freckles likely | Always burns, does not tan | 63.64 | |
| II | Light eyes; light hair | Burns easily, tans poorly | 76.37 | |
| III | Any eye or hair color (very common skin type) | Tans after initial burn | 101.82 | |
| IV | Dark brown hair; medium to heavy pigmentation | Burns minimally, tans easily | 127.28 | |
| V | Dark hair; rarely sun sensitive | Rarely burns, tans darkly easily | 203.64 | |
| VI | N/A | Never burns, always tans darkly | 381.83 |
Ultraviolet Radiation Reflection from Surfaces
Highly reflective surfaces — including concrete, snow, glass, water and polished metals — can increase the surrounding levels of solar UV (see source).
| Material | Reflected Solar UV Rays (%) | Effective UV Index | UV Color |
|---|---|---|---|
| New black roadway (Asphalt) | 4.1% | 2.73 | |
| Old grey roadway (Asphalt) | 8.9% | 2.85 | |
| Footpath (Concrete) | 10.1% | 2.88 | |
| Grasslands (Grass) | 1.2% | 2.65 | |
| Lawn (Grass) | 3.5% | 2.71 | |
| Fiberglass boat deck | 9.1% | 2.86 | |
| White house paint | 22% | 3.2 | |
| Wet beach sand | 7.1% | 2.8 | |
| Dry beach sand | 16.5% | 3.05 | |
| Clay/humus (Soil) | 5% | 2.75 | |
| Open water | 3.3% | 2.71 | |
| Open ocean | 8% | 2.83 | |
| Sea surf/white foam | 27.5% | 3.34 | |
| Snow old/new | 69% | 4.43 | |
| Wood boat deck | 6.6% | 2.79 |
Required Sunlight Exposure for Vitamin D in Nagano
Vitamin D is a hormone that controls calcium levels in the blood. It is needed to develop and maintain healthy bones, muscles and teeth, and is also important for general health. The human body can obtain vitamin D in two ways: diet or sun exposure.
Minutes of sunlight exposure needed for sufficient vitamin D intake (see source).
| Skin Type | Exposure Time (Nagano current UV level: Low) |
|---|---|
| I | 15-20m |
| II | 20-30m |
| III | 30-40m |
| IV | 40-60m |
| V | 60-80m |
| VI | - |
