What official guidance says
- CDC NIOSH (workers in heat) — drink 1 cup (8 oz, about 237 ml) every 15–20 minutes. Short intervals work better than large amounts now and then, and do not drink more than 48 oz (about 1.4 L) per hour.
- Public health agencies — heat advice commonly says to drink regularly even before you feel thirsty; Korea’s disease control agency, for example, adds that people on fluid restriction should ask their doctor first.
The NIOSH numbers are for people working physically in the heat. If you spend the day indoors you do not need to match them, but the principle is the same: spread it out and respect the cap.
A hot-day plan
| When | What to do |
|---|---|
| Before heading out | Have a glass and take a bottle. |
| While outside | Sip before you are thirsty; rest and drink in the shade on long outings. |
| Back indoors | Do not down a liter at once; have a glass or two spread out. |
| Heavy-sweat days | If you drink only water for hours, read drinking too much water too. |
Who needs extra care
- Older adults — they sweat and regulate heat less well and may feel less thirsty (helping older parents).
- People with chronic conditions — heart disease, high blood pressure, diabetes and kidney disease raise heat risk. Agree on fluid amounts with your doctor.
- Outdoor workers — follow your workplace’s heat plan for water, shade and rest.
Hot-day settings in the app
Shorten the interval for the day
In Water Tracker settings, set Interval to 1 hour during hot spells, then put it back to 2 hours afterward.
Raise the goal yourself
The app does not read the weather. Raise the day’s target with the plus button, or set Activity to High and re-apply the recommendation.
Check your time-of-day pattern
The Time-of-day pattern on the History tab shows when you drank over the last 14 days. If it is all after work, add daytime reminders.
FAQ
Is cold water bad in the heat?
The heat guidance discussed here focuses on drinking regularly, not water temperature. Drink at whatever temperature makes it easy to keep going.
Do I need sports drinks?
For everyday heat, water is usually enough. For hours of heavy sweating at work or in sport, see workout days.
Sources: CDC NIOSH, Heat Stress: Hydration · Korea Disease Control and Prevention Agency, heat illness prevention (Korean)
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