WEATHER FOR BUSINESS

We supply weather data to businesses

Free Weather Plugin

Add this forecast to your website



Local Weather

Spa 14 Day Long Range Forecast

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

Belgium

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

Reviewing the forecast for Spa Over the next 14 days and the average daytime maximum temperature will be around 6°C, with a high for the two weeks of 8°C expected on the afternoon of Thursday 12th. The average minimum temperature will be 2°C, dipping to its lowest on the morning of Sunday 15th at -3°C. The coming 14 days will have some days seeing a little precipitation and some days with sleet or snow. It looks like Thursday 12th will have the most precipitation with an accumulation of around 14.0mm. On the whole winds are likely to be moderate.

DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Thu 05
Feb
19:00

SSE
SSE

10 / 14 mph 41 / 35°F 86% 988 mb
Low level cloud: 72%
Mid level cloud: 32%
High level cloud: 71%
Most Significant Cloud Type: low
92%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SE
SE

7 / 11 mph 41 / 36°F 88% 987 mb
Low level cloud: 4%
Mid level cloud: 21%
High level cloud: 56%
Most Significant Cloud Type: medium
35%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Fri 06
Feb
01:00

SE
SE

7 / 13 mph 39 / 33°F 80% 987 mb
Low level cloud: 0%
Mid level cloud: 43%
High level cloud: 100%
Most Significant Cloud Type: medium
47%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SE
SE

4 / 9 mph 38 / 34°F 82% 988 mb
Low level cloud: 1%
Mid level cloud: 59%
High level cloud: 100%
Most Significant Cloud Type: medium
66%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SE
SE

5 / 9 mph 37 / 33°F 85% 989 mb
Low level cloud: 64%
Mid level cloud: 100%
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

SSE
SSE

8 / 13 mph 40 / 34°F 78% 990 mb
Low level cloud: 15%
Mid level cloud: 52%
High level cloud: 100%
Most Significant Cloud Type: medium
98%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

SSE
SSE

7 / 9 mph 41 / 37°F 90% 991 mb
Low level cloud: 94%
Mid level cloud: 77%
High level cloud: 54%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

S
S

5 / 7 mph 42 / 38°F 96% 993 mb
Low level cloud: 96%
Mid level cloud: 85%
High level cloud: 20%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
19:00

S
S

5 / 9 mph 41 / 38°F 97% 995 mb
Low level cloud: 63%
Mid level cloud: 63%
High level cloud: 3%
Most Significant Cloud Type: low
85%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

S
S

5 / 10 mph 39 / 36°F 96% 998 mb
Low level cloud: 41%
Mid level cloud: 60%
High level cloud: 10%
Most Significant Cloud Type: low
63%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sat 07
Feb
01:00

S
S

5 / 8 mph 41 / 38°F 97% 999 mb
Low level cloud: 87%
Mid level cloud: 46%
High level cloud: 8%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SW
SW

6 / 10 mph 42 / 38°F 96% 1000 mb
Low level cloud: 91%
Mid level cloud: 53%
High level cloud: 11%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

S
S

4 / 8 mph 40 / 37°F 95% 1002 mb
Low level cloud: 28%
Mid level cloud: 4%
High level cloud: 9%
Most Significant Cloud Type: low
30%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

S
S

5 / 9 mph 41 / 37°F 88% 1004 mb
Low level cloud: 15%
Mid level cloud: 4%
High level cloud: 33%
Most Significant Cloud Type: low
19%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

S
S

8 / 11 mph 44 / 39°F 81% 1004 mb
Low level cloud: 45%
Mid level cloud: 16%
High level cloud: 44%
Most Significant Cloud Type: low
56%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

S
S

7 / 11 mph 44 / 40°F 82% 1004 mb
Low level cloud: 9%
Mid level cloud: 14%
High level cloud: 18%
Most Significant Cloud Type: low
16%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

SSE
SSE

5 / 8 mph 41 / 38°F 92% 1006 mb
Low level cloud: 39%
Mid level cloud: 19%
High level cloud: 2%
Most Significant Cloud Type: low
46%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SSE
SSE

5 / 9 mph 42 / 38°F 91% 1008 mb
Low level cloud: 9%
Mid level cloud: 50%
High level cloud: 10%
Most Significant Cloud Type: medium
75%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sun 08
Feb
01:00

SSE
SSE

5 / 8 mph 42 / 38°F 91% 1008 mb
Low level cloud: 5%
Mid level cloud: 48%
High level cloud: 32%
Most Significant Cloud Type: medium
64%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SSE
SSE

4 / 8 mph 40 / 38°F 90% 1008 mb
Low level cloud: 22%
Mid level cloud: 45%
High level cloud: 41%
Most Significant Cloud Type: low
42%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SSE
SSE

3 / 6 mph 40 / 38°F 89% 1009 mb
Low level cloud: 80%
Mid level cloud: 46%
High level cloud: 45%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

S
S

2 / 3 mph 43 / 43°F 89% 1010 mb
Low level cloud: 65%
Mid level cloud: 44%
High level cloud: 71%
Most Significant Cloud Type: low
89%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

NNE
NNE

1 / 1 mph 46 / 46°F 75% 1010 mb
Low level cloud: 32%
Mid level cloud: 30%
High level cloud: 17%
Most Significant Cloud Type: low
44%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

ENE
ENE

3 / 4 mph 47 / 46°F 82% 1010 mb
Low level cloud: 62%
Mid level cloud: 44%
High level cloud: 21%
Most Significant Cloud Type: low
80%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

E
E

3 / 4 mph 45 / 44°F 90% 1011 mb
Low level cloud: 64%
Mid level cloud: 47%
High level cloud: 21%
Most Significant Cloud Type: low
83%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SE
SE

3 / 5 mph 43 / 41°F 88% 1011 mb
Low level cloud: 44%
Mid level cloud: 44%
High level cloud: 30%
Most Significant Cloud Type: low
63%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Mon 09
Feb
01:00

SE
SE

4 / 6 mph 40 / 38°F 92% 1011 mb
Low level cloud: 33%
Mid level cloud: 44%
High level cloud: 21%
Most Significant Cloud Type: low
50%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SE
SE

4 / 7 mph 38 / 35°F 94% 1011 mb
Low level cloud: 51%
Mid level cloud: 45%
High level cloud: 17%
Most Significant Cloud Type: low
68%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SSE
SSE

4 / 7 mph 37 / 33°F 95% 1010 mb
Low level cloud: 51%
Mid level cloud: 44%
High level cloud: 20%
Most Significant Cloud Type: low
68%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

SSE
SSE

4 / 6 mph 39 / 36°F 85% 1010 mb
Low level cloud: 34%
Mid level cloud: 57%
High level cloud: 32%
Most Significant Cloud Type: low
57%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

SSE
SSE

5 / 7 mph 43 / 40°F 71% 1009 mb
Low level cloud: 25%
Mid level cloud: 45%
High level cloud: 32%
Most Significant Cloud Type: low
44%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

SSE
SSE

4 / 6 mph 43 / 41°F 69% 1008 mb
Low level cloud: 72%
Mid level cloud: 46%
High level cloud: 4%
Most Significant Cloud Type: low
88%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

SSE
SSE

5 / 9 mph 39 / 36°F 84% 1009 mb
Low level cloud: 11%
Mid level cloud: 38%
High level cloud: 3%
Most Significant Cloud Type: medium
68%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SSE
SSE

7 / 11 mph 37 / 32°F 87% 1009 mb
Low level cloud: 0%
Mid level cloud: 13%
High level cloud: 32%
Most Significant Cloud Type: medium
14%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Tue 10
Feb
01:00

SE
SE

5 / 9 mph 35 / 31°F 89% 1008 mb
Low level cloud: 0%
Mid level cloud: 68%
High level cloud: 9%
Most Significant Cloud Type: medium
68%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SE
SE

5 / 9 mph 35 / 30°F 90% 1007 mb
Low level cloud: 0%
Mid level cloud: 7%
High level cloud: 33%
Most Significant Cloud Type: medium
8%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SE
SE

6 / 10 mph 34 / 29°F 89% 1006 mb
Low level cloud: 1%
Mid level cloud: 99%
High level cloud: 100%
Most Significant Cloud Type: medium
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

SSE
SSE

9 / 14 mph 37 / 30°F 78% 1004 mb
Low level cloud: 0%
Mid level cloud: 97%
High level cloud: 8%
Most Significant Cloud Type: medium
97%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

SSE
SSE

12 / 17 mph 41 / 35°F 69% 1000 mb
Low level cloud: 0%
Mid level cloud: 46%
High level cloud: 0%
Most Significant Cloud Type: medium
45%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

SSE
SSE

11 / 17 mph 42 / 35°F 73% 998 mb
Low level cloud: 8%
Mid level cloud: 66%
High level cloud: 6%
Most Significant Cloud Type: medium
87%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

SSE
SSE

13 / 21 mph 39 / 31°F 88% 995 mb
Low level cloud: 83%
Mid level cloud: 63%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SSE
SSE

12 / 19 mph 39 / 32°F 94% 993 mb
Low level cloud: 88%
Mid level cloud: 87%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Wed 11
Feb
01:00

SSE
SSE

12 / 19 mph 40 / 33°F 94% 989 mb
Low level cloud: 94%
Mid level cloud: 100%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
04:00

WSW
WSW

12 / 25 mph 39 / 32°F 97% 988 mb
Low level cloud: 99%
Mid level cloud: 61%
High level cloud: 76%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

WSW
WSW

17 / 36 mph 39 / 30°F 95% 989 mb
Low level cloud: 99%
Mid level cloud: 75%
High level cloud: 10%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
10:00

WSW
WSW

16 / 28 mph 42 / 35°F 89% 991 mb
Low level cloud: 93%
Mid level cloud: 47%
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

WSW
WSW

15 / 20 mph 45 / 38°F 83% 992 mb
Low level cloud: 82%
Mid level cloud: 20%
High level cloud: 49%
Most Significant Cloud Type: low
94%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

WSW
WSW

13 / 16 mph 46 / 40°F 92% 993 mb
Low level cloud: 92%
Mid level cloud: 93%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

WSW
WSW

13 / 15 mph 44 / 37°F 89% 995 mb
Low level cloud: 82%
Mid level cloud: 45%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

WSW
WSW

13 / 18 mph 42 / 35°F 87% 997 mb
Low level cloud: 96%
Mid level cloud: 76%
High level cloud: 3%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Thu 12
Feb
01:00

SW
SW

12 / 22 mph 41 / 34°F 94% 987 mb
Low level cloud: 100%
Mid level cloud: 92%
High level cloud: 32%
Most Significant Cloud Type: low
100%
0.0 In
07:00

NNW
NNW

8 / 17 mph 35 / 28°F 98% 997 mb
Low level cloud: 97%
Mid level cloud: 64%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
13:00

NNE
NNE

13 / 19 mph 25 / 14°F 84% 1003 mb
Low level cloud: 88%
Mid level cloud: 100%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
19:00

SSE
SSE

3 / 4 mph 43 / 42°F 97% 995 mb
Low level cloud: 96%
Mid level cloud: 70%
High level cloud: 98%
Most Significant Cloud Type: low
100%
0.0 In
Fri 13
Feb
01:00

N
N

3 / 5 mph 33 / 30°F 96% 1001 mb
Low level cloud: 100%
Mid level cloud: 43%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
07:00

W
W

2 / 3 mph 41 / 40°F 99% 994 mb
Low level cloud: 99%
Mid level cloud: 90%
High level cloud: 99%
Most Significant Cloud Type: low
100%
0.0 In
13:00

SSW
SSW

18 / 29 mph 43 / 35°F 78% 997 mb
Low level cloud: 1%
Mid level cloud: 80%
High level cloud: 100%
Most Significant Cloud Type: medium
87%
0.0 In
19:00

W
W

15 / 28 mph 33 / 23°F 93% 998 mb
Low level cloud: 98%
Mid level cloud: 96%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.0 In
Sat 14
Feb
01:00

WNW
WNW

6 / 12 mph 38 / 33°F 99% 985 mb
Low level cloud: 100%
Mid level cloud: 100%
High level cloud: 99%
Most Significant Cloud Type: low
100%
0.0 In
07:00

WSW
WSW

12 / 24 mph 29 / 18°F 94% 998 mb
Low level cloud: 94%
Mid level cloud: 44%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.1 In
13:00

ENE
ENE

3 / 6 mph 42 / 40°F 98% 989 mb
Low level cloud: 100%
Mid level cloud: 74%
High level cloud: 33%
Most Significant Cloud Type: low
100%
0.3 In
19:00

WNW
WNW

12 / 26 mph 31 / 22°F 94% 1005 mb
Low level cloud: 90%
Mid level cloud: 47%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.2 In
Sun 15
Feb
01:00

NE
NE

8 / 15 mph 28 / 20°F 97% 992 mb
Low level cloud: 95%
Mid level cloud: 90%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.2 In
07:00

NW
NW

2 / 5 mph 26 / 23°F 98% 1013 mb
Low level cloud: 91%
Mid level cloud: 4%
High level cloud: 9%
Most Significant Cloud Type: low
93%
0.1 In
13:00

N
N

14 / 27 mph 31 / 21°F 96% 997 mb
Low level cloud: 82%
Mid level cloud: 100%
High level cloud: 96%
Most Significant Cloud Type: low
100%
0.3 In
19:00

E
E

4 / 9 mph 30 / 26°F 93% 1017 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 7%
Most Significant Cloud Type: medium
4%
0.0 In
Mon 16
Feb
01:00

SSW
SSW

4 / 9 mph 25 / 20°F 95% 1009 mb
Low level cloud: 55%
Mid level cloud: 2%
High level cloud: 0%
Most Significant Cloud Type: low
55%
0.0 In
07:00

ESE
ESE

3 / 6 mph 26 / 23°F 91% 1018 mb
Low level cloud: 14%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: low
17%
0.0 In
13:00

SSW
SSW

12 / 23 mph 31 / 21°F 98% 1003 mb
Low level cloud: 89%
Mid level cloud: 100%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.1 In
19:00

ENE
ENE

4 / 8 mph 29 / 25°F 96% 1014 mb
Low level cloud: 62%
Mid level cloud: 45%
High level cloud: 0%
Most Significant Cloud Type: low
77%
0.0 In
Tue 17
Feb
01:00

SSE
SSE

6 / 12 mph 26 / 19°F 97% 1002 mb
Low level cloud: 47%
Mid level cloud: 83%
High level cloud: 100%
Most Significant Cloud Type: low
88%
0.2 In
07:00

NE
NE

9 / 20 mph 16 / 5°F 90% 1010 mb
Low level cloud: 55%
Mid level cloud: 2%
High level cloud: 0%
Most Significant Cloud Type: low
56%
0.0 In
13:00

SSW
SSW

11 / 23 mph 37 / 29°F 99% 989 mb
Low level cloud: 95%
Mid level cloud: 100%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.2 In
19:00

NNE
NNE

9 / 20 mph 20 / 9°F 76% 1010 mb
Low level cloud: 25%
Mid level cloud: 79%
High level cloud: 0%
Most Significant Cloud Type: medium
100%
0.0 In
Wed 18
Feb
01:00

W
W

10 / 21 mph 30 / 22°F 99% 989 mb
Low level cloud: 98%
Mid level cloud: 99%
High level cloud: 3%
Most Significant Cloud Type: low
100%
0.4 In
07:00

N
N

8 / 17 mph 17 / 7°F 93% 1018 mb
Low level cloud: 98%
Mid level cloud: 30%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.0 In
13:00

NNW
NNW

15 / 30 mph 28 / 17°F 95% 1011 mb
Low level cloud: 96%
Mid level cloud: 44%
High level cloud: 33%
Most Significant Cloud Type: low
100%
0.3 In
19:00

ENE
ENE

4 / 8 mph 27 / 23°F 91% 1024 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
Thu 19
Feb
01:00

SE
SE

4 / 8 mph 25 / 20°F 99% 1029 mb
Low level cloud: 10%
Mid level cloud: 0%
High level cloud: 3%
Most Significant Cloud Type: low
10%
0.0 In
07:00

SE
SE

4 / 9 mph 21 / 15°F 94% 1026 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
13:00

SSE
SSE

10 / 21 mph 32 / 24°F 82% 1030 mb
Low level cloud: 0%
Mid level cloud: 46%
High level cloud: 7%
Most Significant Cloud Type: medium
46%
0.0 In
19:00

SE
SE

7 / 14 mph 29 / 22°F 74% 1024 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
Fri 20
Feb
01:00

SSE
SSE

10 / 21 mph 30 / 21°F 80% 1028 mb
Low level cloud: 0%
Mid level cloud: 22%
High level cloud: 32%
Most Significant Cloud Type: medium
23%
0.0 In
07:00

SSE
SSE

6 / 12 mph 27 / 21°F 84% 1025 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 3%
Most Significant Cloud Type: high
2%
0.0 In
13:00

S
S

8 / 17 mph 37 / 31°F 87% 1026 mb
Low level cloud: 31%
Mid level cloud: 78%
High level cloud: 17%
Most Significant Cloud Type: low
60%
0.0 In
19:00

SSE
SSE

5 / 11 mph 37 / 32°F 84% 1030 mb
Low level cloud: 7%
Mid level cloud: 9%
High level cloud: 9%
Most Significant Cloud Type: low
10%
0.0 In

Other Locations Near to Spa

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