Check the PAGASA heat index before you go, protect your skin when the UV index is 3 or higher, drink water regularly, and get out of the sun and cool down at the first signs of heat illness. Heat stroke is a medical emergency: call 911. Water keeps you cooler, but swimmers and paddlers can still overheat, get sunburned and become dehydrated.
This guide is general information, not a substitute for training or medical advice. In an emergency, call 911.
What is the heat index and what do PAGASA's levels mean?
The heat index measures the apparent temperature: what the air and humidity feel like to the human body (Vera Files, 28 April 2023). It is not the temperature on a thermometer.
PAGASA, the national weather bureau under the Department of Science and Technology (DOST), groups the heat index into four categories. The ranges below are as reported by GMA News, quoting PAGASA (GMA News, March 2025):
| Category | Heat index |
|---|---|
| Caution | 27 to 32°C |
| Extreme Caution | 33 to 41°C |
| Danger | 42 to 51°C |
| Extreme Danger | 52°C and above |
What each level means, as reported: at Danger, "heat cramps, exhaustion and heat stroke are probably risks"; at Extreme Danger, "heat stroke is imminent" (GMA News, March 2025). In the Extreme Caution band, exposure can lead to heat cramps and exhaustion (Vera Files, 2023; that article gives the band as 32 to 41°C, so boundaries have shifted slightly over the years).
PAGASA publishes the heat index on its Heat Index page, where the observed chart is an image. Use the category for your area on the day, not the season.
What is the UV index, and how strong is the sun in the Philippines?
The UV index measures how strongly the sun's ultraviolet radiation can damage skin. The WHO's advice is:
| UV index | WHO advice |
|---|---|
| 0 to 2 | Safe to be outside; no protection normally needed |
| 3 to 7 | Protection recommended: seek shade at midday and use clothing, a hat, sunglasses and sunscreen |
| 8 and above | Limit time outside at midday; protective clothing, sunscreen and a hat are essential |
Source: WHO, Radiation: the ultraviolet (UV) index, 20 June 2022-index). The WHO fact sheet adds that sun protection should be used when the UV index reaches 3 or above (WHO, Ultraviolet radiation, 21 June 2022).
UV is strongest in the four hours around solar noon, between about 12 and 2 p.m. depending on location (WHO, 2022-index)). For Manila, one climate-data site lists the maximum UV index as 9 or higher in every month, and 11+ (Extreme) from February to September (weather2travel, Manila climate). This is a travel-information site, not PAGASA, and we found no PAGASA UV forecast. Treat it as a guide only and assume protection is needed on most clear days.
What sunscreen should I use for swimming?
Sunscreen is the last layer, not the first. The WHO says sun protection is best achieved by seeking shade and wearing clothes rather than relying on sunscreen, and that sunscreen should not be used to stay in the sun longer (WHO, 2022). In order:
- Shade. Rest under a tree, umbrella or shelter, especially around midday.
- Clothing. Cover up with a long-sleeved rash guard or shirt. The AAP suggests tightly woven fabric and UPF labels (AAP HealthyChildren.org, updated 9 August 2024).
- Hat. The WHO recommends a broad-brimmed hat to protect the eyes, face, ears and neck (WHO, 2022).
- Sunglasses. Wraparound styles with 99 to 100% UV-A and UV-B protection (WHO, 2022).
- Sunscreen on skin that clothing does not cover. Use broad-spectrum sunscreen.
What number? The sources differ a little, so we show both:
- The American Academy of Pediatrics (AAP) says broad-spectrum sunscreen with SPF 15 or higher, up to SPF 50 (AAP, 2024).
- The American Academy of Dermatology (AAD) recommends broad-spectrum, SPF 30 or higher and water resistant (AAD, Sunscreen FAQs, updated 11 February 2025).
- The Department of Health (DOH) has advised the public to use sun protection lotion in hot weather but, in the report we read, gave no SPF number (SunStar Pampanga, 28 March 2023).
How to use it, according to the AAP: apply 15 to 30 minutes before going out, and reapply every two hours and after swimming, sweating or towelling off (AAP, 2024). The AAD adds that no sunscreen is "waterproof" or "sweatproof", so reapply after you leave the water (AAD, 2025). Keep babies under six months out of direct sunlight; if shade and clothing are not available, the AAP says a small amount of sunscreen may be used on small areas such as the face (AAP, 2024). See also Kids and water safety.
When is it safest to be in the sun?
Try to swim, paddle or play before late morning or in the late afternoon. The AAP advises limiting sun exposure between 10 a.m. and 4 p.m. (AAP, 2024). The DOH has recommended limiting outdoor activity between 10 a.m. and 4 p.m. during hot weather (DOH advisory of March 2025, as reported by the Inquirer; we saw this in search-result text only). A DOH bulletin also advises scheduling strenuous activity in the morning or evening, when it is cooler (DOH bulletin, 27 March 2023, as published by DZRH).
How much should swimmers and paddlers drink?
Drink water before, during and after time on the water, even if you feel cool. The WHO's heat and health fact sheet advises: "Drink water regularly (1 cup of water per hour and at least 2-3 litres per day)" (WHO, 31 July 2026). This is general heat advice, not specific to swimming.
The DOH advises drinking plenty of water and avoiding flavoured drinks such as tea, coffee, soda and alcohol (DOH bulletin, 27 March 2023, as published by DZRH). The Philippine Red Cross (PRC) says to stay hydrated and avoid sugary drinks (Philippine Red Cross, 5 March 2025).
What are the signs of dehydration and heat illness?
The WHO says outdoor and manual workers, athletes and civil protection employees are exposed to excess heat (WHO, 2026). The WHO page lists the exposure groups but does not name swimmers; the same logic applies to people paddling, racing or swimming laps in the sun.
| Condition | Signs reported | What to do |
|---|---|---|
| Heat exhaustion | DOH: warm, flushed skin, faintness or dizziness, weakness, headache. PRC: heavy sweating, paleness, dizziness, vomiting, fainting, moist skin | Move indoors or to shade and lie down with legs raised; remove excess clothing, apply cold water to the skin and fan; if conscious, give cold water (DOH). PRC adds spraying water on the skin and giving an oral rehydration solution |
| Heat stroke (emergency) | DOH: very high fever, convulsions, confusion or delirium, hot dry skin, rapid heartbeat, unconsciousness. PRC: no sweating; red, hot, dry or flushed skin; confusion and disorientation | Call 911 now. While waiting, follow the DOH cooling steps: shade or indoors, ice packs on armpits, wrists, ankles and groin, then hospital right away. The PRC also says to immerse the person in cool water |
Sources: DOH bulletin, 27 March 2023, as published by DZRH and Philippine Red Cross, 5 March 2025. The PRC hotline is 143, available 24/7 (Philippine Red Cross, 2025). The DOH says heat exhaustion "may progress to a heat stroke", so do not wait.
If you notice these signs while on the water, the first DOH step is to get out of the heat: move to shade or indoors. If someone in the water looks like they are in trouble, see Recognising drowning and getting help.
Who is at higher risk of heat illness?
The Philippine Red Cross lists children, the elderly, persons with disabilities and outdoor workers as the groups at highest risk (Philippine Red Cross, 2025). The WHO advises checking regularly on vulnerable people, especially those over 65, those with heart, lung or kidney conditions or a disability, and people living alone, and notes that people in low-quality housing with little access to cooling are often more exposed (WHO, 2026).
A hot-day water checklist
- Check the PAGASA heat index and plan for early morning or late afternoon.
- Bring water and shade, and take breaks out of the sun.
- Wear a rash guard, hat and sunglasses; apply sunscreen and reapply after swimming.
- Do not drink alcohol and then swim.
- Watch children and older relatives closely; they are among the higher-risk groups.
- Know the signs of heat illness and the emergency number, 911.
Related: How to prevent drowning, Open-water swimming safety guide.
Related RESTUBE products
Sources
- PAGASA (DOST). Heat Index. https://www.pagasa.dost.gov.ph/weather/heat-index (chart is an image; category ranges cited from news reports below)
- GMA News. PAGASA: 3 areas under danger-level heat index on March 15, 2025. https://gmanetwork.com/news/scitech/weather/939320/pagasa-3-areas-under-danger-level-heat-index-on-march-15-2025/story
- Vera Files. Fact sheet: the heat index explained, 28 April 2023. https://verafiles.org/articles/vera-files-fact-sheet-the-heat-index-explained
- World Health Organization. Radiation: the ultraviolet (UV) index, 20 June 2022. https://www.who.int/news-room/questions-and-answers/item/radiation-the-ultraviolet-(uv)-index
- World Health Organization. Ultraviolet radiation fact sheet, 21 June 2022. https://www.who.int/news-room/fact-sheets/detail/ultraviolet-radiation
- World Health Organization. Climate change, heat and health fact sheet, 31 July 2026. https://www.who.int/news-room/fact-sheets/detail/climate-change-heat-and-health
- weather2travel. Manila climate (monthly maximum UV index). https://www.weather2travel.com/philippines/manila/climate/?Units=0
- American Academy of Pediatrics. Sun Safety: Information for Parents About Sunburn & Sunscreen, HealthyChildren.org, updated 9 August 2024. https://www.healthychildren.org/English/safety-prevention/at-play/Pages/Sun-Safety.aspx
- American Academy of Dermatology. Sunscreen FAQs, updated 11 February 2025. https://www.aad.org/media/stats-sunscreen
- Department of Health heat bulletin, 27 March 2023, as published by DZRH. https://dzrh.com.ph/post/tips-to-prevent-heat-exhaustion-this-summer-season
- Inquirer. DOH warns vs heat-related illness amid high heat index, March 2025. https://newsinfo.inquirer.net/2039890/doh-warns-vs-heat-related-illness-amid-high-heat-index
- SunStar Pampanga. Brace for extreme heat, public warned, 28 March 2023. https://www.sunstar.com.ph/pampanga/local-news/brace-for-extreme-heat---public-warned
- Philippine Red Cross. Heat advice, 5 March 2025. https://redcross.org.ph/?p=7916
Last reviewed: 12 October 2026.
