WEATHER FOR BUSINESS

We supply weather data to businesses

Free Weather Plugin

Add this forecast to your website



Local Weather

Broadmoor 14 Day Long Range Forecast

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

Surrey, United Kingdom

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

For Broadmoor in the coming two weeks the average daytime maximum temperature will be around 18°C, with a high for the two weeks of 21°C expected on the afternoon of Wednesday 19th. The average minimum temperature will be 11°C, dipping to its lowest on the morning of Wednesday 12th at 6°C. Expect the next 14 days have some days seeing a little precipitation and some days with rain. Predictions are Friday 21st will have the most precipitation with an accumulation of around 23.0mm. On the whole winds are likely to be moderate.

DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Wed 12
Jun
18:00

W
W

7 / 9 mph 61 / 59°F 65% 1019 mb
Low level cloud: 3%
Mid level cloud: 14%
High level cloud: 16%
Most Significant Cloud Type: medium
23%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

WNW
WNW

3 / 5 mph 54 / 52°F 85% 1020 mb
Low level cloud: 4%
Mid level cloud: 19%
High level cloud: 13%
Most Significant Cloud Type: medium
29%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Thu 13
Jun
00:00

SW
SW

4 / 7 mph 49 / 48°F 90% 1019 mb
Low level cloud: 6%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: low
7%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

SSW
SSW

4 / 7 mph 46 / 44°F 91% 1017 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 16%
Most Significant Cloud Type: medium
2%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

SW
SW

4 / 6 mph 49 / 47°F 79% 1016 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 33%
Most Significant Cloud Type: high
32%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

SSW
SSW

11 / 15 mph 57 / 54°F 67% 1015 mb
Low level cloud: 51%
Mid level cloud: 34%
High level cloud: 100%
Most Significant Cloud Type: low
75%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

SSW
SSW

17 / 21 mph 58 / 53°F 69% 1013 mb
Low level cloud: 39%
Mid level cloud: 47%
High level cloud: 100%
Most Significant Cloud Type: low
66%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

SSW
SSW

16 / 21 mph 56 / 52°F 78% 1012 mb
Low level cloud: 10%
Mid level cloud: 46%
High level cloud: 100%
Most Significant Cloud Type: medium
79%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

SSW
SSW

15 / 22 mph 53 / 49°F 87% 1009 mb
Low level cloud: 97%
Mid level cloud: 83%
High level cloud: 11%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

S
S

17 / 26 mph 51 / 46°F 93% 1007 mb
Low level cloud: 99%
Mid level cloud: 91%
High level cloud: 0%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Fri 14
Jun
00:00

SSW
SSW

15 / 23 mph 53 / 49°F 97% 1005 mb
Low level cloud: 100%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

SSW
SSW

10 / 16 mph 55 / 52°F 94% 1003 mb
Low level cloud: 38%
Mid level cloud: 48%
High level cloud: 2%
Most Significant Cloud Type: low
54%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

SW
SW

9 / 14 mph 56 / 53°F 92% 1003 mb
Low level cloud: 54%
Mid level cloud: 59%
High level cloud: 14%
Most Significant Cloud Type: low
76%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

SSW
SSW

11 / 17 mph 57 / 53°F 88% 1003 mb
Low level cloud: 33%
Mid level cloud: 45%
High level cloud: 5%
Most Significant Cloud Type: low
49%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

SSW
SSW

17 / 21 mph 62 / 61°F 69% 1003 mb
Low level cloud: 28%
Mid level cloud: 23%
High level cloud: 0%
Most Significant Cloud Type: low
36%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

SW
SW

19 / 23 mph 63 / 62°F 58% 1002 mb
Low level cloud: 65%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: low
68%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

SSW
SSW

14 / 18 mph 60 / 56°F 71% 1001 mb
Low level cloud: 5%
Mid level cloud: 16%
High level cloud: 98%
Most Significant Cloud Type: medium
34%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

SSW
SSW

9 / 14 mph 54 / 50°F 84% 1001 mb
Low level cloud: 23%
Mid level cloud: 44%
High level cloud: 11%
Most Significant Cloud Type: low
39%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sat 15
Jun
00:00

SSW
SSW

9 / 14 mph 51 / 48°F 95% 1000 mb
Low level cloud: 50%
Mid level cloud: 100%
High level cloud: 0%
Most Significant Cloud Type: low
84%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

WSW
WSW

10 / 16 mph 48 / 44°F 95% 1000 mb
Low level cloud: 32%
Mid level cloud: 9%
High level cloud: 0%
Most Significant Cloud Type: low
35%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

SW
SW

12 / 18 mph 50 / 45°F 90% 1002 mb
Low level cloud: 11%
Mid level cloud: 3%
High level cloud: 20%
Most Significant Cloud Type: low
14%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

SW
SW

20 / 24 mph 57 / 53°F 85% 1002 mb
Low level cloud: 96%
Mid level cloud: 44%
High level cloud: 10%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

SW
SW

21 / 32 mph 58 / 53°F 86% 1002 mb
Low level cloud: 83%
Mid level cloud: 55%
High level cloud: 36%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
15:00

SSW
SSW

16 / 24 mph 54 / 49°F 93% 1002 mb
Low level cloud: 67%
Mid level cloud: 57%
High level cloud: 21%
Most Significant Cloud Type: low
89%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
18:00

SSW
SSW

15 / 24 mph 55 / 50°F 92% 1002 mb
Low level cloud: 66%
Mid level cloud: 56%
High level cloud: 0%
Most Significant Cloud Type: low
85%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

SW
SW

15 / 24 mph 54 / 49°F 92% 1003 mb
Low level cloud: 99%
Mid level cloud: 6%
High level cloud: 0%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sun 16
Jun
00:00

SW
SW

9 / 14 mph 52 / 49°F 93% 1003 mb
Low level cloud: 16%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
16%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

SW
SW

10 / 17 mph 50 / 46°F 91% 1003 mb
Low level cloud: 24%
Mid level cloud: 17%
High level cloud: 1%
Most Significant Cloud Type: low
29%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

SW
SW

12 / 18 mph 54 / 49°F 82% 1004 mb
Low level cloud: 24%
Mid level cloud: 26%
High level cloud: 3%
Most Significant Cloud Type: low
33%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

SW
SW

17 / 22 mph 59 / 56°F 74% 1005 mb
Low level cloud: 66%
Mid level cloud: 21%
High level cloud: 17%
Most Significant Cloud Type: low
75%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

SW
SW

19 / 23 mph 64 / 63°F 62% 1006 mb
Low level cloud: 78%
Mid level cloud: 22%
High level cloud: 16%
Most Significant Cloud Type: low
87%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

SW
SW

17 / 21 mph 64 / 63°F 64% 1006 mb
Low level cloud: 68%
Mid level cloud: 28%
High level cloud: 87%
Most Significant Cloud Type: low
88%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

SW
SW

14 / 18 mph 60 / 60°F 76% 1007 mb
Low level cloud: 23%
Mid level cloud: 74%
High level cloud: 33%
Most Significant Cloud Type: medium
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

SSW
SSW

7 / 12 mph 56 / 53°F 93% 1009 mb
Low level cloud: 23%
Mid level cloud: 43%
High level cloud: 17%
Most Significant Cloud Type: low
40%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Mon 17
Jun
00:00

SSW
SSW

5 / 9 mph 52 / 50°F 96% 1010 mb
Low level cloud: 41%
Mid level cloud: 14%
High level cloud: 5%
Most Significant Cloud Type: low
46%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

SSW
SSW

5 / 9 mph 50 / 49°F 97% 1011 mb
Low level cloud: 50%
Mid level cloud: 15%
High level cloud: 32%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

SW
SW

6 / 8 mph 56 / 53°F 90% 1012 mb
Low level cloud: 39%
Mid level cloud: 13%
High level cloud: 94%
Most Significant Cloud Type: low
54%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

SW
SW

9 / 10 mph 64 / 62°F 65% 1012 mb
Low level cloud: 25%
Mid level cloud: 9%
High level cloud: 21%
Most Significant Cloud Type: low
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

SW
SW

10 / 12 mph 67 / 66°F 60% 1013 mb
Low level cloud: 85%
Mid level cloud: 20%
High level cloud: 2%
Most Significant Cloud Type: low
91%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

SW
SW

9 / 11 mph 69 / 66°F 63% 1013 mb
Low level cloud: 47%
Mid level cloud: 26%
High level cloud: 0%
Most Significant Cloud Type: low
55%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

SW
SW

8 / 11 mph 67 / 65°F 77% 1014 mb
Low level cloud: 39%
Mid level cloud: 17%
High level cloud: 0%
Most Significant Cloud Type: low
44%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

SW
SW

4 / 8 mph 60 / 58°F 92% 1016 mb
Low level cloud: 25%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: low
28%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Tue 18
Jun
00:00

W
W

4 / 7 mph 56 / 56°F 93% 1016 mb
Low level cloud: 7%
Mid level cloud: 7%
High level cloud: 20%
Most Significant Cloud Type: low
12%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

NW
NW

3 / 6 mph 53 / 53°F 95% 1017 mb
Low level cloud: 22%
Mid level cloud: 7%
High level cloud: 55%
Most Significant Cloud Type: low
30%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

NNW
NNW

5 / 7 mph 56 / 53°F 86% 1018 mb
Low level cloud: 8%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
8%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

NNW
NNW

6 / 7 mph 65 / 62°F 66% 1018 mb
Low level cloud: 39%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: low
39%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

NNW
NNW

9 / 10 mph 68 / 67°F 54% 1018 mb
Low level cloud: 3%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

NW
NW

9 / 11 mph 70 / 68°F 52% 1018 mb
Low level cloud: 41%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
41%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

NW
NW

9 / 10 mph 70 / 68°F 62% 1019 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

NNW
NNW

6 / 10 mph 60 / 58°F 77% 1021 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 13%
Most Significant Cloud Type: high
13%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Wed 19
Jun
00:00

WNW
WNW

6 / 14 mph 57 / 56°F 95% 1017 mb
Low level cloud: 12%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
13%
0.0 In
06:00

NW
NW

8 / 17 mph 57 / 56°F 86% 1019 mb
Low level cloud: 12%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
11%
0.0 In
12:00

NNE
NNE

15 / 32 mph 58 / 55°F 93% 1014 mb
Low level cloud: 95%
Mid level cloud: 100%
High level cloud: 22%
Most Significant Cloud Type: low
100%
0.0 In
18:00

S
S

9 / 18 mph 64 / 64°F 81% 1005 mb
Low level cloud: 1%
Mid level cloud: 97%
High level cloud: 100%
Most Significant Cloud Type: medium
100%
0.0 In
Thu 20
Jun
00:00

SW
SW

6 / 13 mph 54 / 52°F 90% 1011 mb
Low level cloud: 1%
Mid level cloud: 14%
High level cloud: 31%
Most Significant Cloud Type: medium
18%
0.0 In
06:00

NW
NW

5 / 10 mph 57 / 56°F 84% 1023 mb
Low level cloud: 6%
Mid level cloud: 3%
High level cloud: 30%
Most Significant Cloud Type: low
10%
0.0 In
12:00

SW
SW

13 / 27 mph 62 / 62°F 82% 1015 mb
Low level cloud: 92%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: low
95%
0.0 In
18:00

E
E

15 / 31 mph 63 / 63°F 71% 1013 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 12%
Most Significant Cloud Type: medium
3%
0.0 In
Fri 21
Jun
00:00

ENE
ENE

13 / 26 mph 58 / 56°F 91% 1013 mb
Low level cloud: 62%
Mid level cloud: 7%
High level cloud: 36%
Most Significant Cloud Type: low
68%
0.0 In
06:00

S
S

9 / 18 mph 59 / 57°F 95% 1007 mb
Low level cloud: 73%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
74%
0.0 In
12:00

SW
SW

7 / 15 mph 63 / 63°F 98% 1010 mb
Low level cloud: 98%
Mid level cloud: 53%
High level cloud: 94%
Most Significant Cloud Type: low
100%
0.8 In
18:00

S
S

17 / 36 mph 62 / 62°F 82% 1002 mb
Low level cloud: 65%
Mid level cloud: 13%
High level cloud: 6%
Most Significant Cloud Type: low
70%
0.0 In
Sat 22
Jun
00:00

S
S

6 / 13 mph 66 / 66°F 96% 1012 mb
Low level cloud: 21%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: low
24%
0.1 In
06:00

S
S

15 / 32 mph 55 / 51°F 97% 1003 mb
Low level cloud: 100%
Mid level cloud: 45%
High level cloud: 32%
Most Significant Cloud Type: low
100%
0.1 In
12:00

SSW
SSW

11 / 23 mph 62 / 62°F 88% 1011 mb
Low level cloud: 55%
Mid level cloud: 47%
High level cloud: 100%
Most Significant Cloud Type: low
83%
0.1 In
18:00

SSW
SSW

14 / 29 mph 59 / 59°F 84% 1001 mb
Low level cloud: 14%
Mid level cloud: 44%
High level cloud: 0%
Most Significant Cloud Type: medium
82%
0.4 In
Sun 23
Jun
00:00

S
S

13 / 27 mph 58 / 56°F 96% 1010 mb
Low level cloud: 100%
Mid level cloud: 70%
High level cloud: 97%
Most Significant Cloud Type: low
100%
0.1 In
06:00

SSW
SSW

9 / 18 mph 59 / 57°F 90% 1005 mb
Low level cloud: 59%
Mid level cloud: 31%
High level cloud: 33%
Most Significant Cloud Type: low
74%
0.0 In
12:00

SSW
SSW

16 / 33 mph 61 / 60°F 96% 1009 mb
Low level cloud: 100%
Mid level cloud: 62%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.1 In
18:00

W
W

12 / 26 mph 66 / 66°F 69% 1012 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 0%
Most Significant Cloud Type: medium
3%
0.1 In
Mon 24
Jun
00:00

SW
SW

10 / 21 mph 59 / 57°F 95% 1010 mb
Low level cloud: 99%
Mid level cloud: 43%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.1 In
06:00

WSW
WSW

4 / 9 mph 61 / 61°F 88% 1017 mb
Low level cloud: 24%
Mid level cloud: 7%
High level cloud: 6%
Most Significant Cloud Type: low
26%
0.0 In
12:00

SSW
SSW

16 / 33 mph 65 / 65°F 69% 1012 mb
Low level cloud: 79%
Mid level cloud: 32%
High level cloud: 0%
Most Significant Cloud Type: low
90%
0.0 In
18:00

S
S

9 / 20 mph 70 / 70°F 69% 1016 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 1%
Most Significant Cloud Type: medium
4%
0.0 In
Tue 25
Jun
00:00

SW
SW

5 / 11 mph 60 / 60°F 97% 1014 mb
Low level cloud: 24%
Mid level cloud: 8%
High level cloud: 0%
Most Significant Cloud Type: low
26%
0.1 In
06:00

SE
SE

4 / 8 mph 60 / 60°F 82% 1014 mb
Low level cloud: 75%
Mid level cloud: 44%
High level cloud: 32%
Most Significant Cloud Type: low
94%
0.0 In
12:00

SW
SW

11 / 23 mph 68 / 68°F 60% 1016 mb
Low level cloud: 84%
Mid level cloud: 27%
High level cloud: 73%
Most Significant Cloud Type: low
100%
0.0 In
18:00

SW
SW

9 / 20 mph 71 / 71°F 66% 1014 mb
Low level cloud: 0%
Mid level cloud: 7%
High level cloud: 0%
Most Significant Cloud Type: medium
6%
0.1 In
Wed 26
Jun
00:00

S
S

4 / 9 mph 61 / 61°F 83% 1014 mb
Low level cloud: 11%
Mid level cloud: 44%
High level cloud: 100%
Most Significant Cloud Type: medium
78%
0.0 In
06:00

SSW
SSW

5 / 10 mph 61 / 61°F 93% 1015 mb
Low level cloud: 69%
Mid level cloud: 19%
High level cloud: 17%
Most Significant Cloud Type: low
78%
0.0 In
12:00

SW
SW

12 / 25 mph 67 / 67°F 73% 1013 mb
Low level cloud: 80%
Mid level cloud: 17%
High level cloud: 0%
Most Significant Cloud Type: low
85%
0.0 In
18:00

SSW
SSW

8 / 17 mph 71 / 71°F 63% 1014 mb
Low level cloud: 0%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: medium
11%
0.0 In
Thu 27
Jun
00:00

WSW
WSW

6 / 13 mph 63 / 63°F 94% 1019 mb
Low level cloud: 17%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: low
20%
0.1 In
06:00

SE
SE

7 / 15 mph 67 / 67°F 86% 1012 mb
Low level cloud: 7%
Mid level cloud: 5%
High level cloud: 3%
Most Significant Cloud Type: low
9%
0.0 In
12:00

W
W

9 / 19 mph 73 / 77°F 56% 1022 mb
Low level cloud: 1%
Mid level cloud: 24%
High level cloud: 0%
Most Significant Cloud Type: medium
25%
0.0 In
18:00

WSW
WSW

5 / 11 mph 61 / 61°F 95% 1010 mb
Low level cloud: 59%
Mid level cloud: 44%
High level cloud: 91%
Most Significant Cloud Type: low
85%
0.1 In

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