Barometric pressure in Ajax
Pressure fell steadily over the past day. It is 6 hPa lower than this time yesterday. The fall is coming to an end: from here it climbs until Tuesday evening.
Sea level reading, as of 14:00 local time.
The past week and the days ahead
The shaded part shows the days already gone. The thicker line is the forecast.
The week ahead
Each day at a glance: how far pressure moves, and the low and high it reaches.
Edges up slowly through the day.
20° / 14°15.6 mmlow 1005 · high 1009 hPa
Rises steadily through the day.
18° / 13°9.0 mmlow 1009 · high 1013 hPa
Rises steadily through the day.
23° / 15°low 1014 · high 1018 hPa
Falls steadily through the day.
23° / 14°low 1013 · high 1018 hPa
Barely moves all day.
23° / 18°8.4 mmlow 1010 · high 1013 hPa
Rises steadily through the day.
24° / 16°low 1013 · high 1019 hPa
Barely moves all day.
22° / 14°low 1019 · high 1022 hPa
Hour by hour
| Hour | Weather and temperature | Rain (mm) | Pressure (hPa) |
|---|---|---|---|
| 00:00 | 19° | 0.6 | 1007 |
| 01:00 | 18° | 0.6 | 1007 |
| 02:00 | 18° | 0.6 | 1006 |
| 03:00 | 17° | 0.3 | 1006 |
| 04:00 | 17° | 0.3 | 1005 |
| 05:00 | 17° | 0.3 | 1005 |
| 06:00 |  17° | 1005 | |
| 07:00 |  16° | 1005 | |
| 08:00 | 17° | 1006 | |
| 09:00 | 18° | 0.1 | 1006 |
| 10:00 | 19° | 0.1 | 1006 |
| 11:00 | 20° | 0.1 | 1005 |
| 12:00 | 20° | 1.8 | 1005 |
| 13:00 | 19° | 1.8 | 1005 |
| 14:00 | 18° | 1.8 | 1006 |
| 15:00 | 18° | 2.0 | 1006 |
| 16:00 | 18° | 2.0 | 1006 |
| 17:00 | 17° | 2.0 | 1006 |
| 18:00 | 17° | 0.4 | 1007 |
| 19:00 | 17° | 0.4 | 1007 |
| 20:00 | 16° | 0.4 | 1008 |
| 21:00 | 15° | 1008 | |
| 22:00 | 15° | 1009 | |
| 23:00 |  14° | 1009 |
Biggest change: Friday, up 6 hPa.
The highest reading, about 1018 hPa, comes on Tuesday evening; it falls from there.
Ajax sits 99 m above sea level, so a barometer in the city reads about 12 hPa lower than the sea-level figure. A home station set to the local reading should show about 994 hPa as of 14:00.
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 Ajax.
Cities nearby
Open one to see its pressure, or search for your own city at the top of the page.
Curious what you are breathing? See the air quality in Ajax today, on our sister site 
airindex.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 Ajax, which stands 99 m above sea level, is in the note above: about 12 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.
