WEATHER FOR BUSINESS

We supply weather data to businesses

Free Weather Plugin

Add this forecast to your website



Local Weather

Airth 14 Day Long Range Forecast

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

Fife, United Kingdom

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

Taking a look at Airth over the coming two weeks and the average daytime maximum temperature will be around 17°C, with a high for the two weeks of 21°C expected on the afternoon of Wednesday 15th. The average minimum temperature will be 7°C, dipping to its lowest on the morning of Tuesday 21st at 2°C. The fortnight ahead will have mostly dry days although Wednesday is likely to see a little rain. It looks like Wednesday 15th will have the most precipitation with an accumulation of around 2.0mm. On the whole winds are likely to be moderate.

DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Wed 15
May
18:00

ENE
ENE

9 / 11 mph 62 / 60°F 88% 1007 mb
Low level cloud: 27%
Mid level cloud: 22%
High level cloud: 58%
Most Significant Cloud Type: low
41%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

NE
NE

5 / 10 mph 52 / 49°F 97% 1008 mb
Low level cloud: 55%
Mid level cloud: 31%
High level cloud: 100%
Most Significant Cloud Type: low
77%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Thu 16
May
00:00

ENE
ENE

4 / 8 mph 49 / 47°F 98% 1008 mb
Low level cloud: 72%
Mid level cloud: 44%
High level cloud: 32%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

ENE
ENE

4 / 6 mph 52 / 51°F 97% 1009 mb
Low level cloud: 97%
Mid level cloud: 45%
High level cloud: 33%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

ENE
ENE

4 / 4 mph 53 / 53°F 97% 1010 mb
Low level cloud: 88%
Mid level cloud: 46%
High level cloud: 12%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

NE
NE

5 / 6 mph 57 / 56°F 92% 1010 mb
Low level cloud: 87%
Mid level cloud: 32%
High level cloud: 10%
Most Significant Cloud Type: low
99%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

NE
NE

7 / 8 mph 61 / 61°F 81% 1010 mb
Low level cloud: 94%
Mid level cloud: 46%
High level cloud: 21%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

ENE
ENE

11 / 12 mph 62 / 62°F 83% 1010 mb
Low level cloud: 93%
Mid level cloud: 16%
High level cloud: 32%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

ENE
ENE

10 / 12 mph 59 / 57°F 86% 1011 mb
Low level cloud: 75%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
76%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

NE
NE

8 / 13 mph 53 / 49°F 92% 1013 mb
Low level cloud: 58%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: low
61%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Fri 17
May
00:00

NE
NE

6 / 10 mph 50 / 47°F 93% 1013 mb
Low level cloud: 47%
Mid level cloud: 5%
High level cloud: 4%
Most Significant Cloud Type: low
48%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

NE
NE

5 / 9 mph 48 / 46°F 96% 1013 mb
Low level cloud: 59%
Mid level cloud: 8%
High level cloud: 8%
Most Significant Cloud Type: low
62%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

NE
NE

5 / 7 mph 54 / 50°F 91% 1013 mb
Low level cloud: 37%
Mid level cloud: 30%
High level cloud: 73%
Most Significant Cloud Type: low
56%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

NE
NE

9 / 10 mph 62 / 59°F 78% 1013 mb
Low level cloud: 43%
Mid level cloud: 19%
High level cloud: 100%
Most Significant Cloud Type: low
61%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

ENE
ENE

11 / 13 mph 67 / 65°F 71% 1013 mb
Low level cloud: 62%
Mid level cloud: 18%
High level cloud: 22%
Most Significant Cloud Type: low
71%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

E
E

11 / 12 mph 66 / 65°F 72% 1014 mb
Low level cloud: 23%
Mid level cloud: 18%
High level cloud: 33%
Most Significant Cloud Type: low
33%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

ENE
ENE

7 / 8 mph 63 / 61°F 80% 1014 mb
Low level cloud: 20%
Mid level cloud: 17%
High level cloud: 45%
Most Significant Cloud Type: low
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

E
E

4 / 8 mph 51 / 49°F 96% 1015 mb
Low level cloud: 22%
Mid level cloud: 14%
High level cloud: 14%
Most Significant Cloud Type: low
28%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sat 18
May
00:00

ESE
ESE

2 / 5 mph 46 / 46°F 98% 1016 mb
Low level cloud: 43%
Mid level cloud: 32%
High level cloud: 12%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

S
S

2 / 3 mph 45 / 45°F 97% 1016 mb
Low level cloud: 41%
Mid level cloud: 25%
High level cloud: 11%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

SSW
SSW

1 / 2 mph 54 / 52°F 92% 1016 mb
Low level cloud: 42%
Mid level cloud: 23%
High level cloud: 0%
Most Significant Cloud Type: low
50%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

N
N

1 / 2 mph 67 / 64°F 75% 1016 mb
Low level cloud: 57%
Mid level cloud: 24%
High level cloud: 10%
Most Significant Cloud Type: low
66%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

ENE
ENE

6 / 7 mph 68 / 67°F 70% 1016 mb
Low level cloud: 85%
Mid level cloud: 16%
High level cloud: 7%
Most Significant Cloud Type: low
91%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

E
E

9 / 11 mph 66 / 64°F 73% 1017 mb
Low level cloud: 21%
Mid level cloud: 25%
High level cloud: 9%
Most Significant Cloud Type: low
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

E
E

10 / 11 mph 59 / 59°F 80% 1017 mb
Low level cloud: 76%
Mid level cloud: 82%
High level cloud: 12%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

ENE
ENE

5 / 6 mph 54 / 53°F 87% 1019 mb
Low level cloud: 57%
Mid level cloud: 90%
High level cloud: 8%
Most Significant Cloud Type: low
89%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sun 19
May
00:00

ENE
ENE

4 / 6 mph 50 / 49°F 92% 1019 mb
Low level cloud: 77%
Mid level cloud: 46%
High level cloud: 89%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

ENE
ENE

4 / 5 mph 50 / 49°F 91% 1019 mb
Low level cloud: 67%
Mid level cloud: 48%
High level cloud: 15%
Most Significant Cloud Type: low
85%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

E
E

6 / 6 mph 52 / 49°F 88% 1020 mb
Low level cloud: 98%
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
09:00

ENE
ENE

7 / 8 mph 50 / 47°F 85% 1021 mb
Low level cloud: 100%
Mid level cloud: 95%
High level cloud: 89%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

ENE
ENE

6 / 8 mph 51 / 48°F 88% 1022 mb
Low level cloud: 100%
Mid level cloud: 89%
High level cloud: 32%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

ENE
ENE

6 / 6 mph 51 / 49°F 90% 1022 mb
Low level cloud: 92%
Mid level cloud: 77%
High level cloud: 24%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

E
E

6 / 6 mph 51 / 49°F 89% 1022 mb
Low level cloud: 92%
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
21:00

ENE
ENE

6 / 7 mph 49 / 46°F 78% 1023 mb
Low level cloud: 81%
Mid level cloud: 19%
High level cloud: 10%
Most Significant Cloud Type: low
88%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Mon 20
May
00:00

ENE
ENE

5 / 6 mph 46 / 44°F 86% 1023 mb
Low level cloud: 17%
Mid level cloud: 4%
High level cloud: 8%
Most Significant Cloud Type: low
19%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

ENE
ENE

4 / 7 mph 39 / 37°F 97% 1023 mb
Low level cloud: 44%
Mid level cloud: 4%
High level cloud: 4%
Most Significant Cloud Type: low
45%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

ENE
ENE

4 / 5 mph 46 / 43°F 90% 1023 mb
Low level cloud: 41%
Mid level cloud: 5%
High level cloud: 2%
Most Significant Cloud Type: low
43%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

E
E

8 / 9 mph 55 / 51°F 65% 1023 mb
Low level cloud: 7%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: low
8%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

E
E

9 / 10 mph 59 / 56°F 56% 1022 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

E
E

10 / 11 mph 59 / 56°F 53% 1021 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

ENE
ENE

9 / 11 mph 55 / 51°F 65% 1021 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 0%
Most Significant Cloud Type: medium
1%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

ENE
ENE

6 / 11 mph 43 / 38°F 94% 1022 mb
Low level cloud: 6%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
6%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Tue 21
May
00:00

NE
NE

4 / 9 mph 38 / 35°F 96% 1021 mb
Low level cloud: 19%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
18%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
03:00

NNE
NNE

4 / 8 mph 37 / 34°F 95% 1020 mb
Low level cloud: 18%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: low
18%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
06:00

NNE
NNE

4 / 5 mph 46 / 44°F 84% 1019 mb
Low level cloud: 81%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: low
81%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
09:00

NE
NE

6 / 7 mph 50 / 47°F 84% 1018 mb
Low level cloud: 82%
Mid level cloud: 1%
High level cloud: 7%
Most Significant Cloud Type: low
82%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
12:00

ENE
ENE

8 / 9 mph 57 / 54°F 75% 1017 mb
Low level cloud: 79%
Mid level cloud: 6%
High level cloud: 48%
Most Significant Cloud Type: low
87%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
15:00

ENE
ENE

12 / 13 mph 62 / 61°F 66% 1016 mb
Low level cloud: 31%
Mid level cloud: 24%
High level cloud: 71%
Most Significant Cloud Type: low
47%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
18:00

ENE
ENE

11 / 13 mph 61 / 60°F 78% 1016 mb
Low level cloud: 30%
Mid level cloud: 43%
High level cloud: 4%
Most Significant Cloud Type: low
45%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
21:00

ENE
ENE

8 / 12 mph 53 / 48°F 89% 1018 mb
Low level cloud: 44%
Mid level cloud: 65%
High level cloud: 0%
Most Significant Cloud Type: low
66%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
DayLocal TimeDirSpeed/
Gust
Temp/
Feels Like
HumidityPressureCloud AmountPrecip AmountWeather
Wed 22
May
00:00

NE
NE

2 / 4 mph 55 / 55°F 98% 1008 mb
Low level cloud: 97%
Mid level cloud: 100%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
06:00

NE
NE

4 / 6 mph 46 / 44°F 80% 1016 mb
Low level cloud: 0%
Mid level cloud: 7%
High level cloud: 17%
Most Significant Cloud Type: medium
7%
0.0 In
12:00

NE
NE

9 / 13 mph 56 / 54°F 91% 1019 mb
Low level cloud: 18%
Mid level cloud: 65%
High level cloud: 100%
Most Significant Cloud Type: medium
100%
0.0 In
18:00

ENE
ENE

13 / 18 mph 55 / 51°F 64% 1019 mb
Low level cloud: 0%
Mid level cloud: 44%
High level cloud: 3%
Most Significant Cloud Type: medium
43%
0.0 In
Thu 23
May
00:00

ENE
ENE

5 / 9 mph 49 / 47°F 95% 1019 mb
Low level cloud: 2%
Mid level cloud: 16%
High level cloud: 100%
Most Significant Cloud Type: medium
26%
0.0 In
06:00

S
S

13 / 20 mph 56 / 52°F 82% 1013 mb
Low level cloud: 100%
Mid level cloud: 65%
High level cloud: 47%
Most Significant Cloud Type: low
100%
0.0 In
12:00

ENE
ENE

7 / 16 mph 61 / 61°F 57% 1027 mb
Low level cloud: 25%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: low
26%
0.0 In
18:00

E
E

12 / 19 mph 62 / 62°F 79% 1025 mb
Low level cloud: 26%
Mid level cloud: 3%
High level cloud: 22%
Most Significant Cloud Type: low
29%
0.0 In
Fri 24
May
00:00

NNE
NNE

4 / 8 mph 43 / 41°F 96% 1029 mb
Low level cloud: 35%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
36%
0.0 In
06:00

ENE
ENE

6 / 10 mph 50 / 47°F 87% 1025 mb
Low level cloud: 83%
Mid level cloud: 2%
High level cloud: 5%
Most Significant Cloud Type: low
84%
0.0 In
12:00

ENE
ENE

9 / 19 mph 63 / 63°F 65% 1026 mb
Low level cloud: 22%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
23%
0.0 In
18:00

ENE
ENE

6 / 10 mph 59 / 59°F 77% 1021 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 96%
Most Significant Cloud Type: high
96%
0.0 In
Sat 25
May
00:00

NE
NE

6 / 13 mph 46 / 43°F 94% 1024 mb
Low level cloud: 1%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: medium
12%
0.0 In
06:00

ENE
ENE

0 / 1 mph 54 / 54°F 90% 1020 mb
Low level cloud: 28%
Mid level cloud: 4%
High level cloud: 7%
Most Significant Cloud Type: low
29%
0.0 In
12:00

ENE
ENE

9 / 19 mph 59 / 59°F 70% 1020 mb
Low level cloud: 8%
Mid level cloud: 42%
High level cloud: 0%
Most Significant Cloud Type: medium
65%
0.0 In
18:00

WSW
WSW

6 / 10 mph 69 / 69°F 60% 1016 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 13%
Most Significant Cloud Type: medium
3%
0.0 In
Sun 26
May
00:00

NNE
NNE

5 / 10 mph 52 / 50°F 88% 1021 mb
Low level cloud: 82%
Mid level cloud: 52%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.0 In
06:00

SW
SW

7 / 12 mph 55 / 53°F 86% 1016 mb
Low level cloud: 14%
Mid level cloud: 48%
High level cloud: 7%
Most Significant Cloud Type: medium
88%
0.0 In
12:00

ENE
ENE

8 / 17 mph 67 / 67°F 74% 1023 mb
Low level cloud: 76%
Mid level cloud: 13%
High level cloud: 0%
Most Significant Cloud Type: low
80%
0.0 In
18:00

W
W

4 / 6 mph 60 / 60°F 69% 1017 mb
Low level cloud: 69%
Mid level cloud: 43%
High level cloud: 0%
Most Significant Cloud Type: low
84%
0.0 In
Mon 27
May
00:00

ENE
ENE

4 / 9 mph 51 / 50°F 97% 1025 mb
Low level cloud: 34%
Mid level cloud: 0%
High level cloud: 2%
Most Significant Cloud Type: low
34%
0.0 In
06:00

WSW
WSW

4 / 7 mph 52 / 51°F 84% 1017 mb
Low level cloud: 17%
Mid level cloud: 42%
High level cloud: 35%
Most Significant Cloud Type: low
35%
0.0 In
12:00

ENE
ENE

4 / 9 mph 72 / 76°F 58% 1023 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
18:00

W
W

11 / 18 mph 59 / 57°F 74% 1017 mb
Low level cloud: 49%
Mid level cloud: 0%
High level cloud: 17%
Most Significant Cloud Type: low
51%
0.0 In
Tue 28
May
00:00

ENE
ENE

5 / 10 mph 54 / 53°F 81% 1019 mb
Low level cloud: 2%
Mid level cloud: 7%
High level cloud: 0%
Most Significant Cloud Type: medium
13%
0.0 In
06:00

WSW
WSW

8 / 13 mph 49 / 46°F 77% 1019 mb
Low level cloud: 19%
Mid level cloud: 0%
High level cloud: 2%
Most Significant Cloud Type: low
19%
0.0 In
12:00

ENE
ENE

13 / 27 mph 66 / 67°F 55% 1016 mb
Low level cloud: 0%
Mid level cloud: 8%
High level cloud: 11%
Most Significant Cloud Type: medium
8%
0.0 In
18:00

WSW
WSW

14 / 23 mph 54 / 50°F 76% 1016 mb
Low level cloud: 94%
Mid level cloud: 46%
High level cloud: 3%
Most Significant Cloud Type: low
100%
0.0 In
Wed 29
May
00:00

NE
NE

5 / 11 mph 51 / 50°F 82% 1015 mb
Low level cloud: 0%
Mid level cloud: 13%
High level cloud: 12%
Most Significant Cloud Type: medium
14%
0.0 In
06:00

WSW
WSW

17 / 28 mph 49 / 43°F 86% 1008 mb
Low level cloud: 95%
Mid level cloud: 44%
High level cloud: 44%
Most Significant Cloud Type: low
100%
0.0 In
12:00

ENE
ENE

10 / 22 mph 70 / 70°F 63% 1012 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 0%
Most Significant Cloud Type: medium
4%
0.0 In
18:00

W
W

17 / 32 mph 55 / 51°F 71% 1008 mb
Low level cloud: 41%
Mid level cloud: 14%
High level cloud: 8%
Most Significant Cloud Type: low
46%
0.1 In
Thu 30
May
00:00

ENE
ENE

4 / 8 mph 53 / 53°F 94% 1010 mb
Low level cloud: 0%
Mid level cloud: 8%
High level cloud: 0%
Most Significant Cloud Type: medium
8%
0.0 In
06:00

WSW
WSW

9 / 17 mph 50 / 47°F 75% 1010 mb
Low level cloud: 8%
Mid level cloud: 7%
High level cloud: 87%
Most Significant Cloud Type: medium
32%
0.0 In
12:00

ENE
ENE

5 / 11 mph 74 / 77°F 62% 1005 mb
Low level cloud: 21%
Mid level cloud: 12%
High level cloud: 15%
Most Significant Cloud Type: low
27%
0.0 In
18:00

WSW
WSW

12 / 22 mph 57 / 55°F 59% 1010 mb
Low level cloud: 1%
Mid level cloud: 78%
High level cloud: 96%
Most Significant Cloud Type: medium
86%
0.0 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