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Quanzhi Ye edited this page Apr 27, 2026 · 4 revisions

Last updated: 2026 April 14

Introduction

7Timer! is a meteorological forecast service developed to assist astronomical observation. It was inspired by Attilla Danko's Clear Sky Chart which provides a similar service for North America. 7Timer! is based on the products generated by the NCEP GFS model. The service was developed and managed by Quanzhi Ye with the help of many, and as of April 2026, it has been mainly maintained by Dimitrios Kechagias in consultation with Quanzhi. 7Timer! has been running since July 2005.

Obtaining forecast data

7Timer! provides four products, each has different emphases:

Product CIVIL CIVIL Light Two-Week-Overview ASTRO METEO
Description 7-day 3-hourly general forecast simplified 7-day forecast 2-week overlook 72-hour forecast for astronomical observations 7-day forecast with detailed meteorological info
Cloud Cover Y Y Y Y
Cloud Profile Y
Lifted Index Y Y Y Y
2m Temperature Y Y Y Y
Max 2m Temp Y Y
Min 2m Temp Y Y
2m Relative Humidity Y Y Y Y
R.H. Profile Y
10m Wind Y Y Y Y Y
Wind Profile Y
Precipitation Type Y Y Y Y Y
Precipitation Amount Y Y
Astro Seeing Y
Atmos Transparency Y
MSL Pressure Y
Snow Depth Y
Weather Type Y Y

Forecast can be obtained by visiting the website or by accessing the application programming interface (API). 7Timer! provides weather maps as well as location-based forecasts for every grid point on the Earth at a resolution of 10 km. The location-based forecasts are encapsulated in a PNG image. Users are welcome to put these images on their websites.

Machine-readable API

7Timer! provides forecast data in XML and JSON format. The API is accessed by a URL with a form similar to

http://www.7timer.info/bin/api.pl?lon=113.17&lat=23.09&product=astro&output=xml

where the parameters are:

Parameter Description
lon [deg, float] WGS84 coordinates of the site.
lat [deg, float] WGS84 coordinates of the site.
ac [km, int] Altitude Correction, only used in ASTRO forecast. Should be 0 (default), 2 or 7.
lang [str] Language. Used in CIVIL, CIVIL Light, TWO, and ASTRO. Permissible values: en.
unit [str] Unit used. Permissible values: metric, british. (At some point "british" will be replaced by "imperial".)
output [str] Output format. Permissible values: xml, json.
tzshift [int] Adjustment of timezone. Permissible values: 0, 1 or -1.
points [int] Number of time points. Use points=80 to get 10-day forecast.

Definition of graphic display and API output

CIVIL and CIVIL Light

Parameter Definition Icon API output (-9999 = invalid) Meaning
cloudcover Cloud Cover 1 0%-6%
2 6%-19%
3 19%-31%
4 31%-44%
5 44%-56%
6 56%-69%
7 69%-81%
8 81%-94%
9 94%-100%
lifted_index Lifted Index -10 Below -7
-6 -7 to -5
-4 -5 to -3
-1 -3 to 0
2 0 to 4
6 4 to 8
10 8 to 11
15 Over 11
prec_type Precipitation Type snow Snow
rain Rain
frzr Freezing rain
icep Ice pellets
none None
prec_amount Precipitation Rate 0 None
1 0-0.25mm/hr
2 0.25-1mm/hr
3 1-4mm/hr
4 4-10mm/hr
5 10-16mm/hr
6 16-30mm/hr
7 30-50mm/hr
8 50-75mm/hr
9 Over 75mm/hr
temp2m 2m Temperature - 2m temperature in Censius
rh2m 2m Relative Humidity - 2m Relative Humidity
wind10m_direction 10m Wind Direction N, NE, E, SE, S, SW, W, NW Classical compass winds
wind10m_speed 10m Wind Speed 1 Below 0.3m/s (calm)
2 0.3-3.4m/s (light)
3 3.4-8.0m/s (moderate)
4 8.0-10.8m/s (fresh)
5 10.8-17.2m/s (strong)
6 17.2-24.5m/s (gale)
7 24.5-32.6m/s (storm)
8 Over 32.6m/s (hurricane)
weather Weather Type clearday, clearnight Total cloud cover less than 20%
pcloudyday, pcloudynight Total cloud cover between 20%-60%
mcloudyday, mcloudynight Total cloud cover between 60%-80%
cloudyday, cloudynight Total cloud cover over over 80%
humidday, humidnight Relative humidity over 90% with total cloud cover less than 60%
lightrainday, lightrainnight Precipitation rate less than 4mm/hr with total cloud cover more than 80%
oshowerday, oshowernight Precipitation rate less than 4mm/hr with total cloud cover between 60%-80%
ishowerday, ishowernight Precipitation rate less than 4mm/hr with total cloud cover less than 60%
lightsnowday, lightsnownight Precipitation rate less than 4mm/hr
rainday, rainnight Precipitation rate over 4mm/hr
snowday, snownight Precipitation rate over 4mm/hr
rainsnowday, rainsnownight Precipitation type to be ice pellets or freezing rain
tsday, tsnight Lifted Index less than -5 with precipitation rate below 4mm/hr
tsrainday, tsrainnight Lifted Index less than -5 with precipitation rate over 4mm/hr

Two-Week-Overview

Parameter Definition Icon API output (-9999 = invalid) Meaning
cloudcover Cloud Cover 1 0%-6%
2 6%-19%
3 19%-31%
4 31%-44%
5 44%-56%
6 56%-69%
7 69%-81%
8 81%-94%
9 94%-100%
lifted_index Lifted Index -10 Below -7
-6 -7 to -5
-4 -5 to -3
-1 -3 to 0
2 0 to 4
6 4 to 8
10 8 to 11
15 Over 11
temp2m_max 2m Max Temperature - 2m max temperature in Censius
temp2m_min 2m Min Temperature - 2m min temperature in Censius
rh2m 2m Relative Humidity - 2m Relative Humidity
wind10m_direction 10m Wind Direction N, NE, E, SE, S, SW, W, NW Classical compass winds
wind10m_speed 10m Wind Speed 1 Below 0.3m/s (calm)
2 0.3-3.4m/s (light)
3 3.4-8.0m/s (moderate)
4 8.0-10.8m/s (fresh)
5 10.8-17.2m/s (strong)
6 17.2-24.5m/s (gale)
7 24.5-32.6m/s (storm)
8 Over 32.6m/s (hurricane)
weather Weather Type clear Total cloud cover less than 20%
pcloudy Total cloud cover between 20%-80%
cloudy Total cloud cover over 80%
rain Rain
snow Snow
ts Thunderstorm
tsrain Thunderstorm with rain

ASTRO

For thumbnails:

Label Definition
Octet-gram of cloud cover, blue is clear while white is cloud. e.g. the "cake" on the left is 0% cloud while the one on the right is 100% cloud.
Astronomical seeing. From left to right: <0.5", 0.5"-0.75", 0.75"-1", 1"-1.25", 1.25"-1.5", 1.5"-2", 2"-2.5", >2.5". In short, the smaller/bluer, the better the seeing condition is.
Atmospheric transparency. From left to right: <0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.85, 0.85-1, >1 (unit: mag per air mass). In short, the fewer bars/bluer, the better the transparency is.
Chances of rain/snow.
Atmospheric instability. From left to right: lifted index between 0 to -3, -3 to -5, and below -5.
Humid weather warning. From left to right: relative humidity between 80%-90%, 90%-95%, and over 95%.
Windy weather warning. From left to right: sustained wind speed between 8.0-10.8m/s (fresh), 10.8-17.2m/s (strong), and over 17.2m/s (gale or above).

For machine-readable API:

Parameter Definition Value (-9999 = undefined) Meaning
cloudcover Cloud Cover 1 0%-6%
2 6%-19%
3 19%-31%
4 31%-44%
5 44%-56%
6 56%-69%
7 69%-81%
8 81%-94%
9 94%-100%
seeing Seeing 1 <0.5"
2 0.5"-0.75"
3 0.75"-1"
4 1"-1.25"
5 1.25"-1.5"
6 1.5"-2"
7 2"-2.5"
8 >2.5"
transparency Transparency 1 <0.3
2 0.3-0.4
3 0.4-0.5
4 0.5-0.6
5 0.6-0.7
6 0.7-0.85
7 0.85-1
8 >1
lifted_index Lifted Index -10 Below -7
-6 -7 to -5
-4 -5 to -3
-1 -3 to 0
2 0 to 4
6 4 to 8
10 8 to 11
15 Over 11
temp2m 2m Temperature - 2m temperature in Celsius
rh2m 2m Relative Humidity -4 0%-5%
-3 5%-10%
-2 10%-15%
-1 15%-20%
0 20%-25%
1 25%-30%
2 30%-35%
3 35%-40%
4 40%-45%
5 45%-50%
6 50%-55%
7 55%-60%
8 60%-65%
9 65%-70%
10 70%-75%
11 75%-80%
12 80%-85%
13 85%-90%
14 90%-95%
15 95%-99%
16 100%
wind10m_direction 10m Wind Direction N, NE, E, SE, S, SW, W, NW
wind10m_speed 10m Wind Speed 1 Below 0.3m/s (calm)
2 0.3-3.4m/s (light)
3 3.4-8.0m/s (moderate)
4 8.0-10.8m/s (fresh)
5 10.8-17.2m/s (strong)
6 17.2-24.5m/s (gale)
7 24.5-32.6m/s (storm)
8 Over 32.6m/s (hurricane)
prec_type Precipitation Type snow, rain, none

About the "Altitude Correction" function: You may consider setting this function if the location of interest is much (over 1000 meters) higher than its surrounding area. 7Timer! will give the forecast at 2km or 7km above the surface of the grid. The Altitude Correction can be set to 2km or 7km.

METEO

Parameter Definition Value (-9999 = undefined) Meaning
cloudcover, highcloud, midcloud, lowcloud Cloud Cover (total, high, mid, low) 1 0%-6%
2 6%-19%
3 19%-31%
4 31%-44%
5 44%-56%
6 56%-69%
7 69%-81%
8 81%-94%
9 94%-100%
rh2m, rh_profile Relative Humidity at 2m and different geopotential layers -4 0%-5%
-3 5%-10%
-2 10%-15%
-1 15%-20%
0 20%-25%
1 25%-30%
2 30%-35%
3 35%-40%
4 40%-45%
5 45%-50%
6 50%-55%
7 55%-60%
8 60%-65%
9 65%-70%
10 70%-75%
11 75%-80%
12 80%-85%
13 85%-90%
14 90%-95%
15 95%-99%
16 100%
wind10m_direction, wind_direction_profile Wind direction at 10m and different geopotential layers Wind direction in degrees
wind10m_speed, wind_speed_profile Wind Speed (10m and profile) 1 Below 0.3m/s (calm)
2 0.3-3.4m/s (light)
3 3.4-8.0m/s (moderate)
4 8.0-10.8m/s (fresh)
5 10.8-17.2m/s (strong)
6 17.2-24.5m/s (gale)
7 24.5-32.6m/s (storm)
8 32.6-36.7m/s (hurricane)
9 36.7-41.4m/s (hurricane+)
10 41.4-46.2m/s (hurricane+)
11 46.2-50.9m/s (hurricane+)
12 50.9-55.9m/s (hurricane+)
13 Over 55.9m/s (hurricane+)
lifted_index Lifted Index -10 Below -7
-6 -7 to -5
-4 -5 to -3
-1 -3 to 0
2 0 to 4
6 4 to 8
10 8 to 11
15 Over 11
temp2m 2m Temperature - 2m temperature in Celsius
msl_pressure MSL Pressure MSL Pressure in hPa
prec_type Precipitation Type snow Snow
rain Rain
frzr Freezing rain
icep Ice pellets
none None
prec_amount Precipitation Amount 0 None
1 0-0.25mm/hr
2 0.25-1mm/hr
3 1-4mm/hr
4 4-10mm/hr
5 10-16mm/hr
6 16-30mm/hr
7 30-50mm/hr
8 50-75mm/hr
9 75+mm/hr
snow_depth Snow Depth 0 None
1 0-1cm
2 1-5cm
3 5-10cm
4 10-25cm
5 25-50cm
6 50-100cm
7 100-150cm
8 150-250cm
9 250+cm

Usage

This service is provided as-is. Feel free to use it as you like. There is no need to ask me for permission if you want to put the forecast graph on your website or use the data for your software (free or paid). I would certainly appreciate a note if you like it, or if you have any suggestions or comments. Note that development has long ceased because I have lost the luxury of having abundant free time (lives...), but I try to keep it running as long and stable as I can.

The Team

The current team members are:

Past team members include:

  • Johnson Lau wrote the automatic data processing pipeline (which is still being used today) in 2009-2010 and provided hardware for the operation.
  • Haiming Tang and the (now-defunct) Chinese Network for Astronomy Popularization provided hardware for 7Timer! in 2011-2018.
  • Zuqiang Li, littlePig and Max helped the early development of 7Timer! in 2005-2006. Liaoshan Shi helped tested every major upgrade.

Icons are designed by Weather Sniffer and Iconbest.

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