WEATHER FOR BUSINESS

We supply weather data to businesses

Free Weather Plugin

Add this forecast to your website



Local Weather

Turnhout 14 Day Long Range Forecast

14 Day weather providing an extended long range forecast outlook for Turnhout

Belgium

Long range weather outlook for Turnhout includes 14 day forecast summary:

Over the next 14 days the Turnhout forecast suggests the average daytime maximum temperature will be around 20°C, with a high for the two weeks of 24°C expected on the afternoon of Monday 13th. The average minimum temperature will be 11°C, dipping to its lowest on the morning of Wednesday 8th at 7°C. Expect the coming 14 days to have some days seeing a little precipitation and some days with rain. The current forecast indicates Tuesday 14th will have the most precipitation with an accumulation of around 12.0mm. On the whole winds are likely to be light.

DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Sun 05
May
19:00

SSE
SSE

3 / 5 mph 62 / 60°F 73% 1008 mb
Low level cloud: 8%
Mid level cloud: 46%
High level cloud: 19%
Most Significant Cloud Type: medium
67%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

E
E

6 / 10 mph 55 / 53°F 80% 1008 mb
Low level cloud: 5%
Mid level cloud: 32%
High level cloud: 100%
Most Significant Cloud Type: medium
49%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Mon 06
May
01:00

ENE
ENE

6 / 10 mph 54 / 52°F 82% 1007 mb
Low level cloud: 72%
Mid level cloud: 82%
High level cloud: 33%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

E
E

5 / 9 mph 53 / 52°F 86% 1006 mb
Low level cloud: 80%
Mid level cloud: 90%
High level cloud: 96%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

E
E

4 / 7 mph 53 / 52°F 91% 1007 mb
Low level cloud: 79%
Mid level cloud: 81%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

E
E

3 / 4 mph 55 / 55°F 92% 1007 mb
Low level cloud: 82%
Mid level cloud: 92%
High level cloud: 37%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

ENE
ENE

3 / 4 mph 57 / 58°F 93% 1009 mb
Low level cloud: 94%
Mid level cloud: 50%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
16:00

E
E

4 / 4 mph 59 / 58°F 90% 1009 mb
Low level cloud: 53%
Mid level cloud: 51%
High level cloud: 100%
Most Significant Cloud Type: low
82%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

ENE
ENE

5 / 6 mph 59 / 57°F 93% 1010 mb
Low level cloud: 31%
Mid level cloud: 43%
High level cloud: 19%
Most Significant Cloud Type: low
48%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

E
E

5 / 6 mph 56 / 55°F 96% 1012 mb
Low level cloud: 34%
Mid level cloud: 77%
High level cloud: 19%
Most Significant Cloud Type: low
62%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Tue 07
May
01:00

ENE
ENE

4 / 7 mph 54 / 53°F 97% 1013 mb
Low level cloud: 49%
Mid level cloud: 30%
High level cloud: 5%
Most Significant Cloud Type: low
60%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

ENE
ENE

4 / 7 mph 53 / 52°F 97% 1014 mb
Low level cloud: 89%
Mid level cloud: 30%
High level cloud: 1%
Most Significant Cloud Type: low
99%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

ENE
ENE

5 / 7 mph 54 / 52°F 96% 1016 mb
Low level cloud: 75%
Mid level cloud: 43%
High level cloud: 13%
Most Significant Cloud Type: low
91%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

ENE
ENE

8 / 10 mph 57 / 54°F 88% 1017 mb
Low level cloud: 62%
Mid level cloud: 29%
High level cloud: 2%
Most Significant Cloud Type: low
72%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

NE
NE

9 / 10 mph 64 / 62°F 63% 1019 mb
Low level cloud: 37%
Mid level cloud: 30%
High level cloud: 5%
Most Significant Cloud Type: low
47%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

NNE
NNE

7 / 9 mph 67 / 64°F 55% 1019 mb
Low level cloud: 54%
Mid level cloud: 25%
High level cloud: 1%
Most Significant Cloud Type: low
62%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

N
N

10 / 14 mph 61 / 60°F 70% 1021 mb
Low level cloud: 1%
Mid level cloud: 18%
High level cloud: 0%
Most Significant Cloud Type: medium
19%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

N
N

6 / 10 mph 53 / 51°F 89% 1023 mb
Low level cloud: 0%
Mid level cloud: 7%
High level cloud: 0%
Most Significant Cloud Type: medium
7%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Wed 08
May
01:00

N
N

5 / 9 mph 49 / 47°F 95% 1024 mb
Low level cloud: 11%
Mid level cloud: 9%
High level cloud: 0%
Most Significant Cloud Type: low
14%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

NNW
NNW

5 / 9 mph 47 / 45°F 96% 1024 mb
Low level cloud: 18%
Mid level cloud: 8%
High level cloud: 47%
Most Significant Cloud Type: low
25%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

NNW
NNW

6 / 8 mph 52 / 48°F 87% 1025 mb
Low level cloud: 28%
Mid level cloud: 11%
High level cloud: 1%
Most Significant Cloud Type: low
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

NNW
NNW

7 / 8 mph 58 / 56°F 72% 1026 mb
Low level cloud: 98%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

N
N

8 / 9 mph 57 / 55°F 76% 1026 mb
Low level cloud: 74%
Mid level cloud: 7%
High level cloud: 0%
Most Significant Cloud Type: low
77%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

N
N

7 / 9 mph 59 / 57°F 72% 1026 mb
Low level cloud: 82%
Mid level cloud: 7%
High level cloud: 0%
Most Significant Cloud Type: low
83%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NNW
NNW

4 / 6 mph 57 / 56°F 83% 1026 mb
Low level cloud: 92%
Mid level cloud: 5%
High level cloud: 20%
Most Significant Cloud Type: low
95%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

N
N

4 / 7 mph 54 / 54°F 90% 1027 mb
Low level cloud: 61%
Mid level cloud: 5%
High level cloud: 2%
Most Significant Cloud Type: low
63%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Thu 09
May
01:00

NNE
NNE

4 / 7 mph 52 / 51°F 94% 1027 mb
Low level cloud: 48%
Mid level cloud: 4%
High level cloud: 6%
Most Significant Cloud Type: low
50%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

NNE
NNE

4 / 6 mph 49 / 49°F 96% 1027 mb
Low level cloud: 40%
Mid level cloud: 5%
High level cloud: 6%
Most Significant Cloud Type: low
42%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

NNE
NNE

2 / 3 mph 54 / 53°F 89% 1027 mb
Low level cloud: 17%
Mid level cloud: 5%
High level cloud: 100%
Most Significant Cloud Type: low
30%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

E
E

3 / 3 mph 62 / 59°F 70% 1027 mb
Low level cloud: 0%
Mid level cloud: 24%
High level cloud: 97%
Most Significant Cloud Type: medium
27%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

SE
SE

1 / 2 mph 70 / 67°F 55% 1026 mb
Low level cloud: 45%
Mid level cloud: 6%
High level cloud: 0%
Most Significant Cloud Type: low
47%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

NNW
NNW

4 / 6 mph 65 / 64°F 67% 1025 mb
Low level cloud: 62%
Mid level cloud: 45%
High level cloud: 9%
Most Significant Cloud Type: low
79%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

N
N

4 / 6 mph 65 / 63°F 75% 1025 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 15%
Most Significant Cloud Type: medium
5%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

NNE
NNE

5 / 9 mph 57 / 56°F 88% 1025 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 100%
Most Significant Cloud Type: medium
9%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Fri 10
May
01:00

NE
NE

4 / 7 mph 54 / 54°F 92% 1025 mb
Low level cloud: 5%
Mid level cloud: 7%
High level cloud: 81%
Most Significant Cloud Type: medium
24%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

NE
NE

3 / 6 mph 52 / 52°F 93% 1024 mb
Low level cloud: 2%
Mid level cloud: 6%
High level cloud: 100%
Most Significant Cloud Type: medium
16%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

ENE
ENE

3 / 4 mph 57 / 56°F 84% 1024 mb
Low level cloud: 3%
Mid level cloud: 6%
High level cloud: 92%
Most Significant Cloud Type: medium
18%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

ENE
ENE

3 / 4 mph 67 / 64°F 66% 1024 mb
Low level cloud: 9%
Mid level cloud: 7%
High level cloud: 29%
Most Significant Cloud Type: low
14%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

ENE
ENE

4 / 4 mph 73 / 70°F 51% 1022 mb
Low level cloud: 48%
Mid level cloud: 12%
High level cloud: 51%
Most Significant Cloud Type: low
58%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

NNE
NNE

5 / 6 mph 71 / 69°F 56% 1021 mb
Low level cloud: 56%
Mid level cloud: 46%
High level cloud: 100%
Most Significant Cloud Type: low
84%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NNE
NNE

6 / 10 mph 67 / 64°F 74% 1021 mb
Low level cloud: 19%
Mid level cloud: 52%
High level cloud: 100%
Most Significant Cloud Type: low
48%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

NNE
NNE

6 / 11 mph 59 / 59°F 82% 1021 mb
Low level cloud: 0%
Mid level cloud: 56%
High level cloud: 32%
Most Significant Cloud Type: medium
57%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sat 11
May
01:00

NE
NE

5 / 11 mph 56 / 55°F 90% 1021 mb
Low level cloud: 0%
Mid level cloud: 32%
High level cloud: 0%
Most Significant Cloud Type: medium
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

NNE
NNE

6 / 11 mph 54 / 53°F 93% 1020 mb
Low level cloud: 0%
Mid level cloud: 28%
High level cloud: 0%
Most Significant Cloud Type: medium
27%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

NE
NE

6 / 9 mph 59 / 56°F 83% 1021 mb
Low level cloud: 1%
Mid level cloud: 28%
High level cloud: 14%
Most Significant Cloud Type: medium
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

NE
NE

7 / 8 mph 68 / 66°F 64% 1020 mb
Low level cloud: 10%
Mid level cloud: 16%
High level cloud: 1%
Most Significant Cloud Type: low
15%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

NNE
NNE

8 / 9 mph 73 / 76°F 54% 1020 mb
Low level cloud: 33%
Mid level cloud: 22%
High level cloud: 0%
Most Significant Cloud Type: low
40%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

NNE
NNE

10 / 12 mph 71 / 69°F 63% 1019 mb
Low level cloud: 26%
Mid level cloud: 20%
High level cloud: 6%
Most Significant Cloud Type: low
33%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NNE
NNE

10 / 14 mph 66 / 64°F 74% 1019 mb
Low level cloud: 0%
Mid level cloud: 10%
High level cloud: 2%
Most Significant Cloud Type: medium
10%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

NE
NE

6 / 11 mph 57 / 56°F 92% 1020 mb
Low level cloud: 11%
Mid level cloud: 7%
High level cloud: 21%
Most Significant Cloud Type: low
16%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Sun 12
May
01:00

NE
NE

5 / 10 mph 55 / 54°F 90% 1022 mb
Low level cloud: 3%
Mid level cloud: 2%
High level cloud: 100%
Most Significant Cloud Type: medium
15%
0.0 In
07:00

NNE
NNE

4 / 8 mph 55 / 55°F 73% 1021 mb
Low level cloud: 0%
Mid level cloud: 15%
High level cloud: 100%
Most Significant Cloud Type: medium
19%
0.0 In
13:00

ENE
ENE

14 / 26 mph 59 / 59°F 44% 1025 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
19:00

NNE
NNE

7 / 13 mph 65 / 65°F 64% 1023 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
Mon 13
May
01:00

ENE
ENE

11 / 19 mph 46 / 40°F 74% 1018 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 0%
Most Significant Cloud Type: medium
1%
0.0 In
07:00

E
E

7 / 13 mph 59 / 59°F 81% 1009 mb
Low level cloud: 8%
Mid level cloud: 43%
High level cloud: 100%
Most Significant Cloud Type: medium
68%
0.0 In
13:00

SE
SE

5 / 8 mph 80 / 81°F 48% 1009 mb
Low level cloud: 3%
Mid level cloud: 11%
High level cloud: 15%
Most Significant Cloud Type: medium
19%
0.0 In
19:00

SE
SE

6 / 12 mph 78 / 82°F 78% 1010 mb
Low level cloud: 0%
Mid level cloud: 11%
High level cloud: 33%
Most Significant Cloud Type: medium
12%
0.0 In
Tue 14
May
01:00

E
E

3 / 6 mph 68 / 68°F 88% 1008 mb
Low level cloud: 0%
Mid level cloud: 23%
High level cloud: 2%
Most Significant Cloud Type: medium
22%
0.0 In
07:00

S
S

5 / 11 mph 64 / 64°F 89% 1009 mb
Low level cloud: 14%
Mid level cloud: 23%
High level cloud: 41%
Most Significant Cloud Type: low
26%
0.0 In
13:00

S
S

4 / 6 mph 78 / 80°F 60% 1006 mb
Low level cloud: 36%
Mid level cloud: 8%
High level cloud: 69%
Most Significant Cloud Type: low
46%
0.0 In
19:00

SE
SE

2 / 4 mph 70 / 70°F 83% 1006 mb
Low level cloud: 16%
Mid level cloud: 54%
High level cloud: 100%
Most Significant Cloud Type: medium
100%
0.1 In
Wed 15
May
01:00

SSE
SSE

3 / 6 mph 68 / 68°F 91% 1002 mb
Low level cloud: 0%
Mid level cloud: 25%
High level cloud: 100%
Most Significant Cloud Type: medium
28%
0.2 In
07:00

SW
SW

2 / 5 mph 64 / 64°F 93% 1008 mb
Low level cloud: 61%
Mid level cloud: 21%
High level cloud: 20%
Most Significant Cloud Type: low
70%
0.5 In
13:00

SW
SW

7 / 15 mph 59 / 59°F 96% 1000 mb
Low level cloud: 100%
Mid level cloud: 82%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.3 In
19:00

ENE
ENE

2 / 3 mph 68 / 68°F 90% 1003 mb
Low level cloud: 9%
Mid level cloud: 52%
High level cloud: 100%
Most Significant Cloud Type: medium
81%
0.2 In
Thu 16
May
01:00

NE
NE

13 / 28 mph 45 / 39°F 92% 1007 mb
Low level cloud: 99%
Mid level cloud: 18%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.1 In
07:00

SW
SW

13 / 27 mph 57 / 54°F 92% 1006 mb
Low level cloud: 85%
Mid level cloud: 8%
High level cloud: 0%
Most Significant Cloud Type: low
88%
0.4 In
13:00

NE
NE

17 / 36 mph 51 / 46°F 73% 1012 mb
Low level cloud: 100%
Mid level cloud: 8%
High level cloud: 3%
Most Significant Cloud Type: low
100%
0.0 In
19:00

NNE
NNE

10 / 21 mph 53 / 50°F 93% 1011 mb
Low level cloud: 100%
Mid level cloud: 44%
High level cloud: 1%
Most Significant Cloud Type: low
100%
0.1 In
Fri 17
May
01:00

ENE
ENE

17 / 37 mph 41 / 33°F 74% 1012 mb
Low level cloud: 95%
Mid level cloud: 44%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
07:00

NNE
NNE

10 / 22 mph 48 / 43°F 78% 1018 mb
Low level cloud: 1%
Mid level cloud: 84%
High level cloud: 4%
Most Significant Cloud Type: medium
87%
0.0 In
13:00

ENE
ENE

16 / 33 mph 47 / 40°F 85% 1014 mb
Low level cloud: 100%
Mid level cloud: 26%
High level cloud: 33%
Most Significant Cloud Type: low
100%
0.1 In
19:00

NNE
NNE

13 / 27 mph 52 / 48°F 66% 1019 mb
Low level cloud: 2%
Mid level cloud: 9%
High level cloud: 12%
Most Significant Cloud Type: medium
13%
0.0 In
Sat 18
May
01:00

NNE
NNE

6 / 14 mph 45 / 41°F 94% 1012 mb
Low level cloud: 99%
Mid level cloud: 46%
High level cloud: 5%
Most Significant Cloud Type: low
100%
0.0 In
07:00

N
N

10 / 20 mph 48 / 44°F 69% 1021 mb
Low level cloud: 27%
Mid level cloud: 0%
High level cloud: 3%
Most Significant Cloud Type: low
27%
0.0 In
13:00

WNW
WNW

5 / 11 mph 54 / 53°F 75% 1012 mb
Low level cloud: 94%
Mid level cloud: 39%
High level cloud: 31%
Most Significant Cloud Type: low
100%
0.0 In
19:00

NNE
NNE

11 / 23 mph 52 / 48°F 69% 1021 mb
Low level cloud: 5%
Mid level cloud: 57%
High level cloud: 0%
Most Significant Cloud Type: medium
70%
0.0 In
Sun 19
May
01:00

WNW
WNW

4 / 8 mph 51 / 50°F 95% 1015 mb
Low level cloud: 15%
Mid level cloud: 7%
High level cloud: 2%
Most Significant Cloud Type: low
17%
0.0 In
07:00

NNE
NNE

8 / 16 mph 47 / 44°F 76% 1024 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
13:00

ENE
ENE

3 / 6 mph 61 / 62°F 60% 1014 mb
Low level cloud: 74%
Mid level cloud: 89%
High level cloud: 27%
Most Significant Cloud Type: low
100%
0.0 In
19:00

N
N

8 / 17 mph 59 / 59°F 65% 1023 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
Mon 20
May
01:00

NE
NE

5 / 11 mph 51 / 50°F 97% 1014 mb
Low level cloud: 93%
Mid level cloud: 55%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
07:00

NNE
NNE

4 / 7 mph 54 / 54°F 78% 1025 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
13:00

NE
NE

5 / 11 mph 63 / 63°F 74% 1013 mb
Low level cloud: 89%
Mid level cloud: 43%
High level cloud: 32%
Most Significant Cloud Type: low
100%
0.0 In
19:00

N
N

9 / 19 mph 58 / 56°F 73% 1023 mb
Low level cloud: 5%
Mid level cloud: 19%
High level cloud: 4%
Most Significant Cloud Type: medium
31%
0.0 In

Other Locations Near to Turnhout

The day label given represents the local day relative to the local time for the location you are looking at.
(More Info)

Day

This time is corrected for local time zones and where possible for daylight saving times.
(More Info)

Local Time

The wind direction we use on this page is the direction the wind is coming from, given in a 16 point compass format.
(More Info)

Dir

This refers to the sustained average wind speed, normally averaged over a period of 10 minutes for up to 3 hrs.
(More Info)

Speed/
Gust

Temperature from our forecast perspective are fairly well defined, they are what we would expect to measure in a standard meteorological screen (in other words, shaded and well ventilated) at 2 metres above ground level.
(More Info)

Temp/
Feels Like

The relative humidity is the percent of saturation humidity, generally calculated in relation to saturated vapour density.
(More Info)

Humidity

The value given is a total predicted for the previous 3 hrs and includes the time of the forecast being looked at.
(More Info)

Precip Amount

The total amount of cloud as a percentage is derived from looking at cloud cover throughout the atmosphere and estimating how these combine when looked at from the ground.
(More Info)

Cloud Amount

Here we try to capture the feel of the weather as an image – it will never be perfect but is useful for a quick overview.
(More Info)

Weather

When we measure for forecast air pressure we are normally doing this relative to a certain height and most commonly relative to Mean Sea Level.
(More Info)

Pressure