Barometric pressure in Tainan
Taking each day as a whole, pressure has fallen slowly. It is 2 hPa lower than this time yesterday. The fall is giving way to a rise that lasts until Tuesday morning.
Sea level reading, as of 23:00 local time.
The past week and the days ahead
The shaded part shows the days already gone. The thicker line is the forecast. The thin grey line is the average over a whole day, so you can see where pressure is heading under the daily up and down.
The week ahead
Each day at a glance: how far pressure moves, and the low and high it reaches.
Eases down slowly through the day.
26° / 25°210.3 mmlow 1000 · high 1004 hPa
Rises steadily through the day.
26° / 26°337.5 mmlow 1001 · high 1006 hPa
Edges up slowly through the day.
26° / 24°50.7 mmlow 1005 · high 1007 hPa
Eases down slowly through the day.
28° / 24°6.3 mmlow 1003 · high 1006 hPa
Eases down slowly through the day.
27° / 24°15.9 mmlow 1000 · high 1004 hPa
Rises steadily through the day.
30° / 24°45.6 mmlow 1001 · high 1005 hPa
Barely moves all day.
30° / 25°9.0 mmlow 1004 · high 1006 hPa
Hour by hour
| Hour | Weather and temperature | Rain (mm) | Pressure (hPa) |
|---|---|---|---|
| 00:00 | 25° | 11.7 | 1004 |
| 01:00 | 25° | 11.7 | 1003 |
| 02:00 | 25° | 11.7 | 1002 |
| 03:00 | 25° | 12.4 | 1002 |
| 04:00 | 25° | 12.4 | 1001 |
| 05:00 | 25° | 12.4 | 1001 |
| 06:00 | 25° | 18.5 | 1001 |
| 07:00 | 25° | 18.5 | 1002 |
| 08:00 | 26° | 18.5 | 1002 |
| 09:00 | 26° | 6.5 | 1002 |
| 10:00 | 26° | 6.5 | 1002 |
| 11:00 | 26° | 6.5 | 1002 |
| 12:00 | 26° | 2.2 | 1002 |
| 13:00 | 26° | 2.2 | 1001 |
| 14:00 | 26° | 2.2 | 1001 |
| 15:00 | 26° | 6.6 | 1000 |
| 16:00 | 26° | 6.6 | 1000 |
| 17:00 | 26° | 6.6 | 1000 |
| 18:00 | 26° | 5.3 | 1000 |
| 19:00 | 26° | 5.3 | 1001 |
| 20:00 | 26° | 5.3 | 1001 |
| 21:00 | 26° | 6.9 | 1002 |
| 22:00 | 26° | 6.9 | 1002 |
| 23:00 | 26° | 6.9 | 1002 |
Biggest change: Monday, up 4 hPa.
Pressure tops out near 1007 hPa on Tuesday morning, and falls after that.
Tainan has a strong daily rhythm: pressure swings about 2 hPa between a regular low and high, at almost the same hours each day. Most of what the graph shows is that daily wave, which is why the change since yesterday says more here than the change over a few hours.
Tainan sits 21 m above sea level, so a barometer in the city reads about 2 hPa lower than the sea-level figure. A home station set to the local reading should show about 1000 hPa as of 23:00.
The hours already past are the model's record of each hour as it passed, anchored to real observations, though not a reading from an instrument in Tainan.
Cities nearby
Open one to see its pressure, or search for your own city at the top of the page.
Out in the sun today? Check the UV level in Tainan, on our sister site 
uvi.today.
Common questions
What is a normal barometric pressure?
Near 1013 hPa at sea level; the exact standard figure, 1013.25 hPa, is the same as 760 mmHg, 29.92 inHg or 101.3 kPa. Anything between roughly 1000 and 1025 hPa is ordinary. Which way it is going matters far more than the number itself.
Why does my own barometer show a different number?
Usually altitude, and sometimes the instrument itself. Weather services correct readings to what they would be at sea level, so that cities can be compared. The figure for Tainan, which stands 21 m above sea level, is in the note above: about 2 hPa below the sea-level reading. If your barometer is already set to sea level and still reads slightly differently, that is the setting on the instrument rather than the weather.
Is a millibar the same as a hectopascal?
Yes. One millibar and one hectopascal are exactly the same amount of pressure, so 1013 mbar and 1013 hPa mean the same thing. The name changed; the number did not.
Does falling pressure mean rain?
Not by itself. Away from the tropics, falling pressure usually means a low is approaching, and lows carry the fronts that bring cloud and rain, so the two often arrive together. But a shallow fall can pass with nothing more than cloud, and rain falls under steady pressure too. The graph tells you a system is on the way, not how wet it will be. The week ahead, just above, shows the rain forecast beside the pressure.
