Vietnam's heat is more brutal than the numbers suggest. A 32°C day with 80% humidity in HCMC feels like 40°C, and lasts longer because your sweat doesn't evaporate. This widget gives real-feel numbers by city and month, plus what to wear and the dengue season caveat.
The thermometer in HCMC says 32°C, but the "feels like" temperature on a 80%-humidity April day is 40°C. Heatstroke is the most common serious traveller health event in Vietnam, and most cases happen in the 11am–3pm window. HCMC is year-round hot and humid (28–35°C, 70–85%). Hà Nội has 4 seasons but summer (May–Aug) hits 30–38°C with heavy humidity. Đà Lạt is the climate escape: 18–25°C year-round. Huế historically the hottest central city (Apr–May).
The "sốt xuất huyết" (dengue fever) season runs May–November. The Aedes mosquito bites during the day, unlike malaria mosquitoes. Long sleeves and DEET-based repellent are the real prevention.
The widget shows actual temp, real-feel, best activity hours, what to wear, and dengue risk.
Actual temperature
26–32°C
Daytime high range.
Real-feel
29–36°C
Heat index including humidity.
Humidity
60–75%
Best activity hours
6–10am, 4–7pm
Dengue risk
Low
What to wear
Linen or loose cotton.
Real-feel uses the heat index. Actual temp + humidity is not what your body feels. At 32°C + 80% humidity, your sweat can't evaporate — you stay wet and hot. The "real-feel" applies the US NWS heat index. Anything 38°C+ real-feel is "danger" for sustained outdoor activity.
The 11am–3pm rule. UV peaks 9–11 and ambient heat peaks 11–3. Most heatstroke cases happen in this window. Safe pattern: outdoor 6–10am, break 11am–3pm (pool, café, museum), outdoor 4–7pm. This is the local pattern.
City personalities. HCMC hot year-round but dry season (Dec–Apr) more bearable. Hà Nội has real seasons — winter (Dec–Feb) 10–18°C; summer (May–Aug) brutal. Đà Lạt is the climate escape: mild 18–25°C. Huế historically hottest in central Vietnam (Apr–May 35–40°C). Sa Pa cold in winter (5–15°C).
Dengue reality. Vietnam has 100,000+ dengue cases/year, mostly May–Nov. The Aedes mosquito bites during the day. Prevention: DEET 20%+ repellent, long sleeves in mosquito-heavy areas.
What to wear. Linen or loose cotton, light colours, closed shoes. No jeans. Hat or umbrella for sun. Sa Pa winter: fleece + windbreaker. HCMC rainy season: quick-dry shoes, light rain jacket.
Travellers plan based on the actual temperature. At 80% humidity, 32°C is brutal. The first 2 days in HCMC are usually the worst — the body needs 4–5 days to acclimatise.
Jeans look nice in photos but stay sweat-soaked for hours in HCMC. Linen trousers or loose cotton pants are the move. Many travellers end up buying local clothes (200,000–500,000 VND) once they arrive.
The dengue mosquito (Aedes aegypti) bites during the day. Most western advice about "evening repellent" is for malaria mosquitoes, which Vietnam doesn't have much of. Use repellent 6am–6pm.
Sa Pa's winter (Dec–Feb) can drop to 5°C at night with possible frost. Pack warm layers. Summer (Jun–Aug) is mild 20–25°C but humid and rainy — not the cool escape you might expect.
HCMC is consistently hotter year-round (28–35°C). Hà Nội has hotter peaks in summer (38°C+) but cooler winters (10–18°C). The "feels like" depends on the month — Hà Nội summer humidity is brutal, but HCMC's year-round humidity is relentless.
Đà Lạt is the climate escape — 18–25°C year-round. Sa Pa is cooler in winter (5–15°C) but warm/humid in summer. If stuck in HCMC or Hà Nội in summer, malls (Vincom, Lotte) and museums are AC refuges.
HCMC rainy season (May–Nov) humidity peaks 85–90%. Hà Nội summer 75–85%. Dry season 60–70% — still muggy by European standards but more bearable.
Dengvaxia is approved in Vietnam but restricted to people with prior dengue exposure. For most first-time travellers, prevention (repellent + long sleeves) is the recommendation. If you develop sudden high fever with severe headache and joint pain during May–Nov, see a doctor.
Heat & Humidity Index is a Vietnam Compass standalone tool. It exists because Vietnam's heat is one of the most common causes of ruined trips — travellers plan based on the thermometer and discover that 32°C with 80% humidity is a different beast than 32°C in Madrid.
Limitations. Monthly averages. Real-feel depends on daily humidity. Dengue risk is approximate.
Data collection. None. This tool is a single HTML file. The widget runs entirely in your browser — no values entered are sent to any server, logged, or stored.
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For reference only. All content is for general informational purposes and is not professional medical, meteorological or travel advice.
Health warning. Heatstroke and dengue are real risks. If you develop sudden fever or heat-related symptoms, see a doctor.
No liability. Vietnam Compass is not responsible for losses arising from reliance on this tool.
Last updated: 2026-10-07.