Hygrometer
Where to get it
The humidity today page reads live outdoor conditions for your location and shows the current dew point with the relative humidity and the grams of water in the air beside it. If you have a temperature and a humidity from somewhere else, the calculator converts them.
The useful thing about today's figure
It is still today's figure this evening.
That is not a small property. Almost everything else in a weather report is a snapshot with a short shelf life — the temperature you read at 8am tells you very little about 3pm, and the relative humidity tells you less. The dew point is different: check it once and you have a number that describes the whole day.
| Time | Temperature | Relative humidity | Dew point |
|---|---|---|---|
| 5am | 62°F | 93% | 60°F |
| 9am | 72°F | 66% | 60°F |
| 1pm | 84°F | 44% | 60°F |
| 5pm | 86°F | 42% | 60°F |
| 9pm | 74°F | 62% | 60°F |
Relative humidity ranged from 93% down to 42% and back. Not a drop of water arrived or left.
So when it does move, pay attention
Precisely because it is normally flat, a moving dew point is a signal rather than noise.
- Rising through the afternoon — humid air is arriving. Tonight will be warmer and heavier than the forecast high suggested, and anything you hoped would dry will not.
- Falling sharply — drier air behind a front. Good drying weather, wider temperature swings, and static a day or two later.
- Climbing towards the air temperature after dark — the gap is closing, which means dew on everything and possibly fog by morning.
The one exception worth knowing: a dip in the early afternoon is usually just mixing. Daytime heating stirs the lower atmosphere and brings drier air down from above, which can drop the surface dew point a few degrees before it recovers after sunset. That is a real change in the air at ground level, not an error.
What today's number tells you to expect
- Under 50°F — a good drying day. Laundry, paint and cut grass all behave.
- 50–60°F — ordinary. Some dampness at dawn, gone by mid-morning.
- 60–65°F — noticeably close. Overnight low will not go far below 60°F.
- 65–70°F — muggy, and the night will not bring relief.
- Above 70°F — very little dries, and sleeping is harder.
The chart has the full scale, and what counts as high goes into what each threshold stops working.
Tomorrow's
Dew point forecasts a day or two out are generally reliable, because they follow air masses and air masses move predictably. The humidity forecast draws the hourly dew point for the next two days — worth a look the evening before anything that depends on the weather behaving.