Fast Forecast

WEATHER FOR BUSINESS

We supply weather data to businesses

Free Weather Plugin

Add this forecast to your website



Local Weather

Rehoboth Beach 14 Day Long Range Forecast

14 Day weather providing an extended long range forecast outlook for Rehoboth Beach

Delaware, United States Of America

Long range weather outlook for Rehoboth Beach includes 14 day forecast summary:

Over the next 14 days the Rehoboth Beach forecast suggests the average daytime maximum temperature will be around 21°C, with a high for the two weeks of 31°C expected on the afternoon of Wednesday 22nd. The mean minimum temperature will be 15°C, dipping to its lowest on the morning of Saturday 18th at 13°C. Expect the next 14 days have some days seeing a little precipitation and some days with rain. It looks like Sunday 19th will have the most precipitation with an accumulation of around 28.0mm. On the whole winds are likely to be moderate.

DayLocal TimeDirSpeed/
Gust		Temp/
Feels Like		HumidityPressureCloud AmountPrecip AmountWeather
Mon 13
May		01:00

ESE
ESE

 20 / 34 mph 55 / 50°F 91% 1008 mb
Low level cloud: 25%
Mid level cloud: 98%
High level cloud: 100%
Most Significant Cloud Type: medium
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

ESE
ESE

 31 / 53 mph 55 / 49°F 95% 1000 mb
Low level cloud: 100%
Mid level cloud: 98%
High level cloud: 98%
Most Significant Cloud Type: low
100%
Expect 0.3 In of precipitation over the past 3 hours.
0.3 In
07:00

SSE
SSE

 37 / 65 mph 61 / 61°F 94% 995 mb
Low level cloud: 100%
Mid level cloud: 48%
High level cloud: 22%
Most Significant Cloud Type: low
100%
Expect 0.2 In of precipitation over the past 3 hours.
0.2 In
10:00

S
S

 6 / 7 mph 62 / 60°F 76% 1020 mb
Low level cloud: 35%
Mid level cloud: 6%
High level cloud: 0%
Most Significant Cloud Type: low
36%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

SSE
SSE

 15 / 17 mph 65 / 64°F 78% 1019 mb
Low level cloud: 3%
Mid level cloud: 3%
High level cloud: 1%
Most Significant Cloud Type: low
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

S
S

 18 / 21 mph 65 / 64°F 79% 1018 mb
Low level cloud: 11%
Mid level cloud: 3%
High level cloud: 0%
Most Significant Cloud Type: low
11%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

S
S

 16 / 19 mph 62 / 62°F 84% 1018 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 100%
Most Significant Cloud Type: high
99%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

S
S

 15 / 21 mph 58 / 56°F 84% 1018 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 71%
Most Significant Cloud Type: high
70%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Tue 14
May		19:00

S
S

 12 / 15 mph 65 / 64°F 85% 1015 mb
Low level cloud: 2%
Mid level cloud: 45%
High level cloud: 83%
Most Significant Cloud Type: medium
53%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SSE
SSE

 10 / 19 mph 61 / 61°F 88% 1014 mb
Low level cloud: 0%
Mid level cloud: 64%
High level cloud: 89%
Most Significant Cloud Type: medium
67%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Wed 15
May		01:00

S
S

 7 / 15 mph 59 / 59°F 88% 1013 mb
Low level cloud: 4%
Mid level cloud: 57%
High level cloud: 43%
Most Significant Cloud Type: medium
70%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SE
SE

 8 / 16 mph 58 / 56°F 94% 1011 mb
Low level cloud: 16%
Mid level cloud: 47%
High level cloud: 100%
Most Significant Cloud Type: medium
95%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

ESE
ESE

 9 / 17 mph 58 / 56°F 95% 1011 mb
Low level cloud: 53%
Mid level cloud: 97%
High level cloud: 100%
Most Significant Cloud Type: low
98%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

ESE
ESE

 10 / 13 mph 61 / 60°F 95% 1011 mb
Low level cloud: 55%
Mid level cloud: 97%
High level cloud: 97%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
13:00

E
E

 15 / 18 mph 63 / 63°F 95% 1010 mb
Low level cloud: 92%
Mid level cloud: 59%
High level cloud: 7%
Most Significant Cloud Type: low
100%
Expect 0.1 In of precipitation over the past 3 hours.
0.1 In
16:00

ENE
ENE

 18 / 21 mph 63 / 63°F 96% 1008 mb
Low level cloud: 78%
Mid level cloud: 76%
High level cloud: 42%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NE
NE

 20 / 23 mph 62 / 62°F 96% 1008 mb
Low level cloud: 84%
Mid level cloud: 54%
High level cloud: 32%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

NE
NE

 22 / 27 mph 60 / 60°F 95% 1008 mb
Low level cloud: 94%
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
Thu 16
May		01:00

NNE
NNE

 20 / 28 mph 58 / 55°F 95% 1006 mb
Low level cloud: 100%
Mid level cloud: 44%
High level cloud: 26%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

NNE
NNE

 19 / 29 mph 58 / 54°F 94% 1007 mb
Low level cloud: 100%
Mid level cloud: 45%
High level cloud: 32%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

N
N

 20 / 29 mph 58 / 54°F 92% 1008 mb
Low level cloud: 100%
Mid level cloud: 45%
High level cloud: 14%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

N
N

 22 / 29 mph 60 / 60°F 88% 1008 mb
Low level cloud: 98%
Mid level cloud: 16%
High level cloud: 3%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

N
N

 22 / 28 mph 61 / 61°F 90% 1008 mb
Low level cloud: 99%
Mid level cloud: 56%
High level cloud: 3%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

NNE
NNE

 22 / 26 mph 62 / 62°F 91% 1009 mb
Low level cloud: 100%
Mid level cloud: 46%
High level cloud: 0%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NNE
NNE

 20 / 23 mph 60 / 60°F 95% 1010 mb
Low level cloud: 99%
Mid level cloud: 26%
High level cloud: 0%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

NNE
NNE

 15 / 18 mph 59 / 59°F 95% 1012 mb
Low level cloud: 100%
Mid level cloud: 16%
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 17
May		01:00

NNE
NNE

 13 / 21 mph 57 / 54°F 94% 1012 mb
Low level cloud: 82%
Mid level cloud: 18%
High level cloud: 0%
Most Significant Cloud Type: low
88%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

NNE
NNE

 12 / 21 mph 56 / 53°F 92% 1012 mb
Low level cloud: 53%
Mid level cloud: 22%
High level cloud: 13%
Most Significant Cloud Type: low
61%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

NNE
NNE

 13 / 22 mph 57 / 53°F 90% 1014 mb
Low level cloud: 60%
Mid level cloud: 15%
High level cloud: 12%
Most Significant Cloud Type: low
66%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

NE
NE

 15 / 21 mph 59 / 56°F 89% 1015 mb
Low level cloud: 100%
Mid level cloud: 12%
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

NE
NE

 12 / 16 mph 62 / 61°F 87% 1015 mb
Low level cloud: 74%
Mid level cloud: 7%
High level cloud: 0%
Most Significant Cloud Type: low
76%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

ENE
ENE

 11 / 14 mph 63 / 61°F 88% 1016 mb
Low level cloud: 58%
Mid level cloud: 8%
High level cloud: 0%
Most Significant Cloud Type: low
60%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

ENE
ENE

 11 / 14 mph 61 / 60°F 93% 1015 mb
Low level cloud: 17%
Mid level cloud: 4%
High level cloud: 0%
Most Significant Cloud Type: low
18%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

ENE
ENE

 10 / 14 mph 58 / 56°F 93% 1015 mb
Low level cloud: 28%
Mid level cloud: 1%
High level cloud: 9%
Most Significant Cloud Type: low
29%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sat 18
May		01:00

ENE
ENE

 6 / 7 mph 58 / 57°F 93% 1015 mb
Low level cloud: 55%
Mid level cloud: 2%
High level cloud: 100%
Most Significant Cloud Type: low
67%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

E
E

 7 / 10 mph 56 / 54°F 95% 1015 mb
Low level cloud: 74%
Mid level cloud: 4%
High level cloud: 72%
Most Significant Cloud Type: low
83%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

ESE
ESE

 6 / 9 mph 56 / 55°F 93% 1016 mb
Low level cloud: 76%
Mid level cloud: 46%
High level cloud: 32%
Most Significant Cloud Type: low
95%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

ESE
ESE

 11 / 12 mph 63 / 61°F 90% 1014 mb
Low level cloud: 46%
Mid level cloud: 10%
High level cloud: 19%
Most Significant Cloud Type: low
51%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

SE
SE

 11 / 12 mph 66 / 65°F 91% 1014 mb
Low level cloud: 50%
Mid level cloud: 53%
High level cloud: 93%
Most Significant Cloud Type: low
79%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

SE
SE

 11 / 13 mph 66 / 66°F 92% 1012 mb
Low level cloud: 76%
Mid level cloud: 43%
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

SE
SE

 12 / 14 mph 64 / 63°F 93% 1011 mb
Low level cloud: 43%
Mid level cloud: 45%
High level cloud: 77%
Most Significant Cloud Type: low
67%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

SE
SE

 13 / 19 mph 59 / 59°F 93% 1010 mb
Low level cloud: 77%
Mid level cloud: 44%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sun 19
May		01:00

SSE
SSE

 16 / 21 mph 61 / 61°F 98% 1008 mb
Low level cloud: 100%
Mid level cloud: 56%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.2 In of precipitation over the past 3 hours.
0.2 In
04:00

SSE
SSE

 14 / 26 mph 59 / 59°F 99% 1006 mb
Low level cloud: 97%
Mid level cloud: 65%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.4 In of precipitation over the past 3 hours.
0.4 In
07:00

SSE
SSE

 9 / 18 mph 60 / 59°F 99% 1006 mb
Low level cloud: 98%
Mid level cloud: 46%
High level cloud: 100%
Most Significant Cloud Type: low
100%
Expect 0.2 In of precipitation over the past 3 hours.
0.2 In
10:00

E
E

 5 / 7 mph 64 / 64°F 99% 1005 mb
Low level cloud: 99%
Mid level cloud: 56%
High level cloud: 41%
Most Significant Cloud Type: low
100%
Expect 0.2 In of precipitation over the past 3 hours.
0.2 In
13:00

NNE
NNE

 9 / 10 mph 68 / 68°F 98% 1005 mb
Low level cloud: 93%
Mid level cloud: 28%
High level cloud: 73%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

NNW
NNW

 12 / 14 mph 69 / 68°F 97% 1005 mb
Low level cloud: 88%
Mid level cloud: 31%
High level cloud: 0%
Most Significant Cloud Type: low
98%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NNW
NNW

 13 / 15 mph 66 / 65°F 97% 1005 mb
Low level cloud: 99%
Mid level cloud: 22%
High level cloud: 19%
Most Significant Cloud Type: low
100%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

N
N

 12 / 14 mph 63 / 63°F 97% 1006 mb
Low level cloud: 89%
Mid level cloud: 30%
High level cloud: 16%
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
Mon 20
May		01:00

NE
NE

 21 / 45 mph 52 / 47°F 83% 1011 mb
Low level cloud: 93%
Mid level cloud: 49%
High level cloud: 6%
Most Significant Cloud Type: low
100%
0.4 In
07:00

SE
SE

 7 / 15 mph 60 / 60°F 81% 1010 mb
Low level cloud: 73%
Mid level cloud: 46%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.0 In
13:00

E
E

 9 / 19 mph 54 / 51°F 63% 1018 mb
Low level cloud: 27%
Mid level cloud: 21%
High level cloud: 1%
Most Significant Cloud Type: low
34%
0.0 In
19:00

ESE
ESE

 9 / 19 mph 64 / 64°F 98% 1004 mb
Low level cloud: 93%
Mid level cloud: 43%
High level cloud: 32%
Most Significant Cloud Type: low
100%
0.3 In
Tue 21
May		01:00

WSW
WSW

 9 / 19 mph 51 / 47°F 68% 1022 mb
Low level cloud: 0%
Mid level cloud: 18%
High level cloud: 0%
Most Significant Cloud Type: medium
17%
0.0 In
07:00

N
N

 7 / 15 mph 58 / 56°F 95% 1004 mb
Low level cloud: 99%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.2 In
19:00

SSW
SSW

 9 / 16 mph 73 / 77°F 90% 1008 mb
Low level cloud: 0%
Mid level cloud: 23%
High level cloud: 0%
Most Significant Cloud Type: medium
23%
0.0 In
Wed 22
May		01:00

S
S

 18 / 38 mph 64 / 64°F 85% 1007 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 5%
Most Significant Cloud Type: medium
4%
0.0 In
07:00

N
N

 12 / 21 mph 62 / 62°F 91% 1012 mb
Low level cloud: 11%
Mid level cloud: 46%
High level cloud: 0%
Most Significant Cloud Type: medium
75%
0.0 In
13:00

SW
SW

 16 / 26 mph 84 / 90°F 65% 1005 mb
Low level cloud: 0%
Mid level cloud: 18%
High level cloud: 62%
Most Significant Cloud Type: medium
20%
0.0 In
19:00

S
S

 9 / 15 mph 67 / 67°F 76% 1012 mb
Low level cloud: 8%
Mid level cloud: 44%
High level cloud: 86%
Most Significant Cloud Type: medium
68%
0.0 In
Thu 23
May		01:00

W
W

 9 / 19 mph 67 / 67°F 92% 1006 mb
Low level cloud: 5%
Mid level cloud: 12%
High level cloud: 32%
Most Significant Cloud Type: low
12%
0.1 In
07:00

NE
NE

 9 / 17 mph 58 / 56°F 97% 1010 mb
Low level cloud: 99%
Mid level cloud: 16%
High level cloud: 15%
Most Significant Cloud Type: low
100%
0.2 In
13:00

SSE
SSE

 8 / 17 mph 73 / 78°F 96% 1004 mb
Low level cloud: 34%
Mid level cloud: 49%
High level cloud: 99%
Most Significant Cloud Type: low
63%
0.3 In
19:00

ENE
ENE

 18 / 34 mph 63 / 63°F 93% 1010 mb
Low level cloud: 97%
Mid level cloud: 44%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.1 In
Fri 24
May		01:00

NNE
NNE

 7 / 14 mph 58 / 57°F 99% 1003 mb
Low level cloud: 56%
Mid level cloud: 46%
High level cloud: 0%
Most Significant Cloud Type: low
71%
0.5 In
07:00

NE
NE

 22 / 44 mph 57 / 52°F 93% 1012 mb
Low level cloud: 100%
Mid level cloud: 43%
High level cloud: 100%
Most Significant Cloud Type: low
100%
0.5 In
13:00

NE
NE

 23 / 47 mph 64 / 64°F 90% 1008 mb
Low level cloud: 99%
Mid level cloud: 31%
High level cloud: 17%
Most Significant Cloud Type: low
100%
0.1 In
19:00

NE
NE

 16 / 31 mph 59 / 59°F 79% 1017 mb
Low level cloud: 0%
Mid level cloud: 43%
High level cloud: 98%
Most Significant Cloud Type: medium
46%
0.0 In
Sat 25
May		01:00

NNE
NNE

 17 / 37 mph 53 / 48°F 88% 1014 mb
Low level cloud: 97%
Mid level cloud: 88%
High level cloud: 0%
Most Significant Cloud Type: low
100%
0.1 In
07:00

NE
NE

 17 / 34 mph 56 / 52°F 77% 1020 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
13:00

N
N

 12 / 25 mph 56 / 53°F 71% 1019 mb
Low level cloud: 69%
Mid level cloud: 53%
High level cloud: 0%
Most Significant Cloud Type: low
87%
0.0 In
19:00

ENE
ENE

 11 / 22 mph 60 / 60°F 73% 1024 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 4%
Most Significant Cloud Type: high
3%
0.0 In
Sun 26
May		01:00

W
W

 9 / 19 mph 53 / 50°F 79% 1019 mb
Low level cloud: 0%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: medium
10%
0.0 In
07:00

ENE
ENE

 12 / 23 mph 56 / 53°F 71% 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

NW
NW

 9 / 19 mph 67 / 67°F 55% 1020 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: medium
5%
0.0 In
19:00

E
E

 11 / 21 mph 62 / 62°F 77% 1027 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 81%
Most Significant Cloud Type: high
80%
0.0 In
Mon 27
May		01:00

WNW
WNW

 8 / 17 mph 60 / 60°F 69% 1020 mb
Low level cloud: 0%
Mid level cloud: 10%
High level cloud: 25%
Most Significant Cloud Type: medium
10%
0.0 In
07:00

ESE
ESE

 7 / 13 mph 57 / 56°F 80% 1026 mb
Low level cloud: 1%
Mid level cloud: 4%
High level cloud: 0%
Most Significant Cloud Type: medium
5%
0.0 In
13:00

S
S

 11 / 23 mph 70 / 70°F 62% 1019 mb
Low level cloud: 0%
Mid level cloud: 8%
High level cloud: 99%
Most Significant Cloud Type: medium
11%
0.0 In
19:00

SSE
SSE

 10 / 19 mph 64 / 64°F 84% 1022 mb
Low level cloud: 0%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: medium
11%
0.0 In
Tue 28
May		01:00

SSW
SSW

 18 / 38 mph 67 / 67°F 80% 1015 mb
Low level cloud: 29%
Mid level cloud: 74%
High level cloud: 0%
Most Significant Cloud Type: low
55%
0.0 In
07:00

SSW
SSW

 9 / 17 mph 63 / 63°F 88% 1018 mb
Low level cloud: 30%
Mid level cloud: 45%
High level cloud: 100%
Most Significant Cloud Type: low
57%
0.0 In
13:00

SSW
SSW

 20 / 41 mph 67 / 67°F 93% 1012 mb
Low level cloud: 100%
Mid level cloud: 91%
High level cloud: 90%
Most Significant Cloud Type: low
100%
0.4 In
19:00

S
S

 14 / 28 mph 69 / 69°F 87% 1015 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 7%
Most Significant Cloud Type: medium
2%
0.0 In

Other Locations Near to Rehoboth Beach

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