Fast Forecast

WEATHER FOR BUSINESS

We supply weather data to businesses

Free Weather Plugin

Add this forecast to your website



Local Weather

Sierra At Tahoe 14 Day Long Range Forecast

14 Day weather providing an extended long range forecast outlook for Sierra At Tahoe

California, United States Of America

Long range weather outlook for Sierra At Tahoe includes 14 day forecast summary:

For Sierra At Tahoe in the coming two weeks the average daytime maximum temperature will be around 18°C, with a high for the two weeks of 23°C expected on the afternoon of Tuesday 17th. The mean minimum temperature will be 5°C, dipping to its lowest on the morning of Thursday 12th at 2°C. The fortnight ahead will remain predominantly dry. On the whole winds are likely to be light.

DayLocal TimeDirSpeed/
Gust		Temp/
Feels Like		HumidityPressureCloud AmountPrecip AmountWeather
Wed 11
Mar		01:00

ESE
ESE

 2 / 4 mph 29 / 28°F 76% 1030 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
04:00

ESE
ESE

 3 / 6 mph 29 / 27°F 71% 1031 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 0%
Most Significant Cloud Type: medium
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SE
SE

 2 / 4 mph 31 / 30°F 62% 1031 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: medium
1%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

WSW
WSW

 4 / 4 mph 50 / 49°F 39% 1028 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
13:00

W
W

 5 / 6 mph 55 / 53°F 40% 1027 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 9%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

W
W

 5 / 6 mph 54 / 52°F 46% 1027 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 10%
Most Significant Cloud Type: medium
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

ESE
ESE

 2 / 5 mph 40 / 39°F 75% 1030 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 38%
Most Significant Cloud Type: medium
6%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

ESE
ESE

 3 / 7 mph 38 / 36°F 69% 1031 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 13%
Most Significant Cloud Type: medium
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Thu 12
Mar		22:00

SE
SE

 3 / 6 mph 41 / 39°F 52% 1025 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 33%
Most Significant Cloud Type: high
32%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Fri 13
Mar		01:00

SSE
SSE

 2 / 4 mph 40 / 40°F 38% 1024 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 51%
Most Significant Cloud Type: high
51%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

SSE
SSE

 2 / 5 mph 40 / 39°F 35% 1023 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 19%
Most Significant Cloud Type: high
18%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SE
SE

 2 / 4 mph 42 / 41°F 31% 1022 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 55%
Most Significant Cloud Type: high
55%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

SW
SW

 5 / 5 mph 58 / 56°F 20% 1019 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 21%
Most Significant Cloud Type: high
20%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

WSW
WSW

 7 / 8 mph 60 / 60°F 22% 1017 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 88%
Most Significant Cloud Type: high
88%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

WSW
WSW

 5 / 6 mph 57 / 55°F 33% 1017 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 41%
Most Significant Cloud Type: high
41%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

S
S

 2 / 4 mph 44 / 44°F 56% 1018 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 66%
Most Significant Cloud Type: high
65%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

S
S

 2 / 5 mph 42 / 42°F 45% 1018 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 32%
Most Significant Cloud Type: high
31%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sat 14
Mar		01:00

S
S

 2 / 5 mph 40 / 39°F 41% 1018 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 21%
Most Significant Cloud Type: high
20%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

S
S

 2 / 5 mph 39 / 38°F 39% 1018 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 40%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

SSW
SSW

 2 / 4 mph 40 / 40°F 38% 1018 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 98%
Most Significant Cloud Type: medium
6%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

WSW
WSW

 5 / 6 mph 55 / 52°F 29% 1016 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: medium
1%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

W
W

 9 / 11 mph 57 / 55°F 38% 1016 mb
Low level cloud: 0%
Mid level cloud: 6%
High level cloud: 8%
Most Significant Cloud Type: medium
6%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

WSW
WSW

 6 / 7 mph 55 / 53°F 48% 1016 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 3%
Most Significant Cloud Type: medium
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

NE
NE

 1 / 2 mph 44 / 44°F 79% 1019 mb
Low level cloud: 0%
Mid level cloud: 9%
High level cloud: 0%
Most Significant Cloud Type: medium
8%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

ENE
ENE

 5 / 11 mph 41 / 38°F 79% 1021 mb
Low level cloud: 0%
Mid level cloud: 8%
High level cloud: 1%
Most Significant Cloud Type: medium
8%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Sun 15
Mar		01:00

ENE
ENE

 6 / 14 mph 40 / 36°F 77% 1021 mb
Low level cloud: 0%
Mid level cloud: 7%
High level cloud: 61%
Most Significant Cloud Type: medium
9%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

ENE
ENE

 7 / 15 mph 38 / 33°F 72% 1022 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 1%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

ENE
ENE

 7 / 15 mph 40 / 34°F 65% 1023 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 0%
Most Significant Cloud Type: medium
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

ENE
ENE

 7 / 8 mph 56 / 53°F 30% 1021 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 8%
Most Significant Cloud Type: medium
1%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
13:00

ENE
ENE

 6 / 7 mph 62 / 60°F 25% 1020 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 2%
Most Significant Cloud Type: medium
3%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

ENE
ENE

 6 / 6 mph 61 / 59°F 28% 1019 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 6%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
19:00

ENE
ENE

 6 / 13 mph 46 / 43°F 45% 1023 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 1%
Most Significant Cloud Type: high
0%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

ENE
ENE

 7 / 14 mph 43 / 39°F 48% 1024 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 43%
Most Significant Cloud Type: medium
4%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Mon 16
Mar		01:00

ENE
ENE

 7 / 15 mph 43 / 38°F 49% 1024 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 10%
Most Significant Cloud Type: high
10%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

ENE
ENE

 7 / 15 mph 42 / 37°F 51% 1023 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: high
0%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

ENE
ENE

 8 / 16 mph 43 / 38°F 54% 1024 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
10:00

ENE
ENE

 6 / 7 mph 62 / 61°F 31% 1021 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
13:00

ENE
ENE

 6 / 7 mph 67 / 66°F 27% 1019 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: high
0%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
16:00

ENE
ENE

 6 / 6 mph 67 / 65°F 32% 1018 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
19:00

ENE
ENE

 7 / 14 mph 50 / 47°F 54% 1021 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: high
0%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
22:00

ENE
ENE

 7 / 15 mph 48 / 45°F 58% 1022 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 4%
Most Significant Cloud Type: medium
2%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
Tue 17
Mar		01:00

ENE
ENE

 7 / 15 mph 46 / 42°F 62% 1022 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 4%
Most Significant Cloud Type: medium
2%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
04:00

E
E

 7 / 14 mph 44 / 40°F 62% 1021 mb
Low level cloud: 0%
Mid level cloud: 3%
High level cloud: 3%
Most Significant Cloud Type: medium
2%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
07:00

E
E

 6 / 14 mph 46 / 42°F 60% 1022 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 0%
Most Significant Cloud Type: medium
2%
Expect 0.0 In of precipitation over the past 3 hours.
0.0 In
10:00

ESE
ESE

 2 / 3 mph 67 / 65°F 31% 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
13:00

WSW
WSW

 6 / 7 mph 74 / 73°F 22% 1016 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
16:00

WSW
WSW

 7 / 8 mph 69 / 67°F 30% 1016 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
19:00

SE
SE

 1 / 3 mph 56 / 56°F 58% 1020 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
22:00

ESE
ESE

 3 / 6 mph 52 / 52°F 57% 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
DayLocal TimeDirSpeed/
Gust		Temp/
Feels Like		HumidityPressureCloud AmountPrecip AmountWeather
Wed 18
Mar		04:00

E
E

 4 / 8 mph 50 / 49°F 55% 1020 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 0%
Most Significant Cloud Type: medium
1%
0.0 In
10:00

SW
SW

 7 / 8 mph 67 / 67°F 21% 1016 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
16:00

WSW
WSW

 9 / 11 mph 69 / 69°F 35% 1018 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
22:00

ESE
ESE

 3 / 6 mph 52 / 52°F 48% 1020 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
Thu 19
Mar		04:00

SE
SE

 3 / 6 mph 49 / 48°F 46% 1020 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
10:00

SW
SW

 6 / 7 mph 66 / 66°F 17% 1019 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
16:00

SW
SW

 12 / 13 mph 66 / 66°F 47% 1018 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 1%
Most Significant Cloud Type: medium
2%
0.0 In
22:00

S
S

 3 / 6 mph 51 / 51°F 71% 1022 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 0%
Most Significant Cloud Type: medium
4%
0.0 In
Fri 20
Mar		04:00

SSW
SSW

 4 / 9 mph 42 / 39°F 85% 1019 mb
Low level cloud: 0%
Mid level cloud: 11%
High level cloud: 0%
Most Significant Cloud Type: medium
11%
0.0 In
10:00

SW
SW

 10 / 12 mph 62 / 62°F 32% 1018 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 15%
Most Significant Cloud Type: high
14%
0.0 In
16:00

SW
SW

 8 / 10 mph 45 / 40°F 85% 1015 mb
Low level cloud: 29%
Mid level cloud: 79%
High level cloud: 2%
Most Significant Cloud Type: low
56%
0.0 In
22:00

S
S

 4 / 8 mph 43 / 41°F 55% 1018 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 15%
Most Significant Cloud Type: high
14%
0.0 In
Sat 21
Mar		04:00

SW
SW

 8 / 12 mph 30 / 23°F 92% 1018 mb
Low level cloud: 24%
Mid level cloud: 32%
High level cloud: 0%
Most Significant Cloud Type: low
35%
0.0 In
10:00

SW
SW

 10 / 11 mph 52 / 48°F 19% 1014 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
16:00

W
W

 15 / 19 mph 29 / 18°F 41% 1018 mb
Low level cloud: 0%
Mid level cloud: 12%
High level cloud: 0%
Most Significant Cloud Type: medium
12%
0.0 In
22:00

SE
SE

 0 / 1 mph 33 / 33°F 84% 1019 mb
Low level cloud: 0%
Mid level cloud: 10%
High level cloud: 0%
Most Significant Cloud Type: medium
9%
0.0 In
Sun 22
Mar		04:00

S
S

 1 / 2 mph 16 / 16°F 88% 1025 mb
Low level cloud: 8%
Mid level cloud: 19%
High level cloud: 0%
Most Significant Cloud Type: low
14%
0.1 In
10:00

WSW
WSW

 7 / 9 mph 45 / 41°F 10% 1016 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
16:00

WNW
WNW

 9 / 12 mph 30 / 22°F 33% 1018 mb
Low level cloud: 0%
Mid level cloud: 6%
High level cloud: 0%
Most Significant Cloud Type: medium
5%
0.0 In
22:00

SSE
SSE

 1 / 3 mph 34 / 34°F 23% 1019 mb
Low level cloud: 0%
Mid level cloud: 7%
High level cloud: 28%
Most Significant Cloud Type: medium
8%
0.0 In
Mon 23
Mar		04:00

ENE
ENE

 6 / 10 mph 17 / 9°F 61% 1024 mb
Low level cloud: 0%
Mid level cloud: 4%
High level cloud: 6%
Most Significant Cloud Type: medium
4%
0.0 In
10:00

WSW
WSW

 6 / 7 mph 48 / 45°F 13% 1014 mb
Low level cloud: 0%
Mid level cloud: 5%
High level cloud: 2%
Most Significant Cloud Type: medium
5%
0.0 In
16:00

ENE
ENE

 4 / 5 mph 39 / 37°F 22% 1016 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
22:00

ESE
ESE

 1 / 2 mph 35 / 35°F 49% 1017 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 0%
Most Significant Cloud Type: medium
1%
0.0 In
Tue 24
Mar		04:00

ENE
ENE

 9 / 18 mph 21 / 10°F 49% 1027 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 7%
Most Significant Cloud Type: high
7%
0.0 In
10:00

WSW
WSW

 6 / 6 mph 51 / 49°F 31% 1016 mb
Low level cloud: 0%
Mid level cloud: 0%
High level cloud: 0%
Most Significant Cloud Type: high
0%
0.0 In
16:00

E
E

 4 / 5 mph 47 / 45°F 24% 1020 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 13%
Most Significant Cloud Type: high
13%
0.0 In
22:00

SE
SE

 2 / 3 mph 39 / 39°F 61% 1020 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 8%
Most Significant Cloud Type: medium
2%
0.0 In
Wed 25
Mar		04:00

ESE
ESE

 2 / 5 mph 33 / 32°F 51% 1025 mb
Low level cloud: 0%
Mid level cloud: 2%
High level cloud: 100%
Most Significant Cloud Type: medium
6%
0.0 In
10:00

WSW
WSW

 8 / 9 mph 50 / 47°F 32% 1015 mb
Low level cloud: 0%
Mid level cloud: 1%
High level cloud: 42%
Most Significant Cloud Type: high
42%
0.0 In
16:00

WSW
WSW

 2 / 3 mph 46 / 46°F 38% 1019 mb
Low level cloud: 0%
Mid level cloud: 72%
High level cloud: 100%
Most Significant Cloud Type: medium
75%
0.0 In
22:00

SW
SW

 12 / 16 mph 37 / 28°F 95% 1016 mb
Low level cloud: 63%
Mid level cloud: 46%
High level cloud: 0%
Most Significant Cloud Type: low
79%
0.2 In
Thu 26
Mar		04:00

ESE
ESE

 0 / 1 mph 38 / 38°F 55% 1018 mb
Low level cloud: 0%
Mid level cloud: 57%
High level cloud: 100%
Most Significant Cloud Type: medium
61%
0.0 In
10:00

SW
SW

 11 / 14 mph 38 / 30°F 57% 1016 mb
Low level cloud: 0%
Mid level cloud: 55%
High level cloud: 30%
Most Significant Cloud Type: medium
56%
0.0 In
16:00

WSW
WSW

 2 / 3 mph 42 / 41°F 82% 1015 mb
Low level cloud: 13%
Mid level cloud: 92%
High level cloud: 16%
Most Significant Cloud Type: medium
100%
0.0 In
22:00

SW
SW

 16 / 23 mph 34 / 23°F 96% 1015 mb
Low level cloud: 71%
Mid level cloud: 43%
High level cloud: 1%
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