What is the NWS wind chill formula?

The 2001 NWS index is WC = 35.74 + 0.6215T - 35.75 V^0.16 + 0.4275 T V^0.16 with air temperature T in °F and wind speed V in mph. The metric form uses 13.12, 0.6215, -11.37 and 0.3965 with °C and km/h.

When is the wind chill formula valid?

Only at or below 50 °F (10 °C) with a wind speed above 3 mph (about 4.8 km/h). Outside that envelope wind chill is not defined and the effective temperature is close to the actual air temperature.

How fast does exposed skin freeze?

At -20 to -29 °F wind chill, frostbite can reach exposed skin in 10-30 minutes; at -30 to -39 in 5-10 minutes; at -50 °F or colder in 5 minutes or less. The planner highlights the exact band and time range.

Does wind chill affect water, cars or objects?

No. Wind chill accelerates heat loss from warm, heat-generating bodies like people and animals; inanimate objects cool only to the actual air temperature, never below it, though wind makes them cool faster.

What should I wear when the wind chill is dangerous?

Cover every inch of skin with a balaclava or gaiter, goggles, hat and windproof mittens over liners; wear a wind shell over insulating layers, keep cotton and damp fabric off the skin, and check partners for white or waxy patches on the face and fingers.

Wind Chill & Frostbite Calculator风寒与冻伤时间计算器

The NWS wind-chill formula, dual-unit results and exposed-skin freeze-time bands for your summit day. NWS 风寒公式、双单位结果与冲顶日裸露皮肤冻伤时间分级。

🧭 Weather & Navigation天气与导航求救 🌬 NWS 2001 index · winterNWS 2001 指数 · 冬季 📅 Updated Oct 20262026 年 10 月更新

How the wind chill calculator works

Moving air strips the thin warm layer from your skin, so the body loses heat far faster than the thermometer alone suggests. The result is not a measured temperature but an equivalent temperature: how cold the wind and air together feel to exposed human skin.

The NWS 2001 formula

The U.S. National Weather Service index used in Canada and the United States is WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16 with temperature T in °F and wind V in mph. The official metric form is WC = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16 in °C and km/h. The two vectors on the NWS chart are reproduced exactly: 0 °F in a 15 mph wind gives about −19 °F, and −20 °F at 30 mph gives about −53 °F. The equation is only valid at or below 50 °F (10 °C) when wind exceeds 3 mph; above that the calculator reports that the index does not apply.

From wind chill to frostbite time

The NWS frostbite bands assume exposed skin: down to −10 °F the risk is low with 30 or more minutes of exposure; −11 to −19 °F stays low around the 30-minute mark; −20 to −29 °F raises the risk to 10–30 minutes; −30 to −39 °F means 5–10 minutes; −40 to −49 °F still 5–10 minutes; and −50 °F or colder freezes flesh in 5 minutes or less. The active row is highlighted so the number on screen maps directly to a decision on the ridge.

What wind chill does and does not do

Wind chills people and animals, which generate heat; it does not drive inanimate objects below the actual air temperature. It does, however, accelerate whole-body hypothermia even above freezing, especially in wet clothing, and gusts or exposed-ridge wind should be used instead of sheltered trailhead readings. Cover all skin, block the wind with a shell, prefer mittens with liners, and watch your partner's face for white or waxy patches.

风寒计算器原理

流动的空气会不断带走皮肤表面那层被身体焐暖的薄空气，使人体散热远快于温度计读数。风寒温度不是实测温度，而是“等效温度”——风与气温共同作用在裸露皮肤上的体感。

NWS 2001 公式

美国国家气象局（NWS，美加通用）指数为 WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16，T 为华氏气温、V 为英里/小时风速；官方公制形式为 WC = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16（°C、km/h）。NWS 图表上的两个标准向量精确复现：0 °F、15 mph 约为 −19 °F；−20 °F、30 mph 约为 −53 °F。公式仅在气温 ≤ 50 °F（10 °C）且风速 > 3 mph 时有效；超出范围时工具提示不适用。

从风寒到冻伤时间

NWS 冻伤分级以裸露皮肤为前提：−10 °F 以上风险低（暴露 30 分钟以上）；−11～−19 °F 低风险、约 30 分钟量级；−20～−29 °F 风险升高、10–30 分钟；−30～−39 °F 约 5–10 分钟；−40～−49 °F 仍为 5–10 分钟；−50 °F 或更低 5 分钟以内即可冻伤。你当前所在的一行会高亮，屏幕数字直接对应山脊上的决策。

风寒能做什么、不能做什么

风寒只对持续产热的人与动物有意义，不会让无生命物体降到实际气温以下；但它会加速全身失温——即使气温在冰点以上、尤其衣物潮湿时。请用暴露山脊风与阵风（而非背风山口风速）填写：遮盖全部皮肤、外层防风、优先并指手套加内胆，并互查同伴面部与手指有无发白、蜡状斑块。

Frequently asked questions常见问题

Why does the calculator show “not applicable”?为什么显示“不适用”？

The NWS formula is calibrated only at or below 50 °F (10 °C) with wind above 3 mph. In mild or calm conditions effective temperature is close to the actual air temperature, so no wind-chill number is published for that envelope.NWS 公式只在气温 ≤ 10 °C（50 °F）、风速 > 3 mph 时标定。温和或无风环境中体感接近实际气温，该区间没有官方风寒值。

Which wind speed should I enter on a summit?冲顶时风速该填哪个？

Use the strongest sustained wind expected on the exposed section, because ridgetops accelerate wind well beyond trailhead forecasts. Plan as if gusts were the steady value.按暴露路段预计遇到的最大持续风速填——山脊风速常远大于山口预报，并按阵风等同持续风来规划。

Are the frostbite times for covered skin?冻伤时间是针对遮盖的皮肤吗？

No — the NWS bands describe exposed skin. Proper windproof cover, mittens and goggles extend protection substantially, but pressure points, gaps and damp clothing can still freeze quickly.不是——NWS 分级针对裸露皮肤。合格的防风遮盖、并指手套与风镜能显著延长保护时间，但压迫点、缝隙与湿衣处仍可能快速冻伤。

Can wind chill freeze water that is above freezing?风寒能让零上的水结冰吗？

No. Objects cannot cool below the actual air temperature; wind only speeds cooling to that temperature. The danger of wind chill is its effect on living bodies and on hypothermia risk.不能。物体不会被风寒降到实际气温以下，风只是加快降到气温的速度。风寒的危险在于对活体与失温风险的作用。

Wind chill and hypothermia — what is the link?风寒与失温有什么关系？

Driven air multiplies convective heat loss, so hypothermia can develop at temperatures well above freezing when clothes are wet or rest stops are long. Cross-check the Hypothermia Risk Assessor (T05) whenever the party is tired or damp.气流会成倍放大对流散热，因此衣物潮湿或长时间停留时，气温远高于冰点也可能失温。队伍疲劳或受潮时请配合 T05 失温风险评估器判断。