Teslin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Teslin clear sky chart from 2005-11-06 to 2024-01-14.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
37%
22724
5%
74894
4%
22669
39%
22669
11%
59372

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
33%
1014
6%
3249
5%
1011
35%
1011
8%
2764
January11th to 20thNight
26%
817
5%
2934
5%
817
28%
817
6%
2482
January21st to endNight
31%
880
8%
3168
5%
880
36%
880
8%
2600
February1st to 10thNight
40%
800
11%
2643
9%
800
42%
800
12%
2048
February11th to 20thNight
35%
783
7%
2450
6%
780
36%
780
10%
1998
February21st to endNight
45%
644
12%
1971
8%
644
48%
644
18%
1436
March1st to 10thNight
44%
720
14%
2160
12%
720
45%
720
17%
1587
March11th to 20thNight
36%
719
6%
2128
6%
719
38%
719
12%
1697
March21st to endNight
45%
594
9%
1980
8%
594
47%
594
13%
1486
April1st to 10thNight
48%
540
7%
1746
6%
540
50%
540
15%
1301
April11th to 20thNight
51%
533
8%
1484
6%
533
52%
533
20%
1091
April21st to endNight
45%
500
1%
1400
1%
500
46%
500
16%
1068
May1st to 10thNight
50%
360
0%
1220
0%
360
50%
360
15%
880
May11th to 20thNight
49%
354
0%
1062
0%
354
49%
354
21%
720
May21st to endNight
54%
388
0%
1018
0%
388
54%
388
25%
726
June1st to 10thNight
49%
286
0%
826
0%
286
49%
286
19%
607
June11th to 20thNight
53%
180
0%
720
0%
180
53%
180
15%
493
June21st to endNight
54%
180
0%
720
0%
180
54%
180
15%
489
July1st to 10thNight
56%
175
0%
700
0%
175
56%
175
15%
472
July11th to 20thNight
45%
344
0%
967
0%
344
45%
344
13%
769
July21st to endNight
49%
394
0%
1116
0%
372
50%
372
16%
836
August1st to 10thNight
49%
358
0%
1111
0%
356
49%
356
17%
795
August11th to 20thNight
41%
529
2%
1419
1%
529
41%
529
15%
1103
August21st to endNight
39%
594
3%
1624
3%
594
39%
594
12%
1327
September1st to 10thNight
38%
540
5%
1718
4%
540
39%
540
12%
1353
September11th to 20thNight
47%
583
12%
1843
11%
583
49%
583
17%
1332
September21st to endNight
31%
720
7%
1983
4%
720
33%
720
10%
1648
October1st to 10thNight
38%
720
8%
2208
7%
720
39%
720
13%
1717
October11th to 20thNight
29%
720
6%
2340
5%
720
31%
720
8%
1934
October21st to endNight
33%
855
5%
2754
4%
855
34%
855
9%
2243
November1st to 10thNight
30%
830
5%
2776
5%
830
32%
830
8%
2314
November11th to 20thNight
29%
850
3%
2928
3%
850
31%
850
6%
2524
November21st to endNight
24%
1002
4%
3192
2%
1002
26%
1002
7%
2727
December1st to 10thNight
25%
1040
5%
3230
3%
1040
27%
1040
6%
2859
December11th to 20thNight
33%
1039
6%
3992
4%
1039
35%
1039
7%
3272
December21st to endNight
33%
1139
4%
6114
6%
1114
36%
1114
5%
4674

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
11%11%5%10%9%5%7%6%6%7%22%
74511
Night
9%14%6%11%10%5%7%6%6%7%19%
75238
TransparencyDay
58%11%15%13%4
74150
Night
60%9%13%13%4
75118
SeeingDay
16%11%22%26%18%6%
16046
Night
14%7%21%33%21%4
22733

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
9%14%6%14%15%6%8%6%5%8%10%
930
11th to 20thDay
11%17%8%16%11%5%6%5%5%6%8%
1098
21st to endDay
8%18%6%11%11%5%7%7%6%6%13%
1188
February1st to 10thDay
6%14%5%12%9%47%7%8%7%22%
1316
11th to 20thDay
6%17%8%11%9%5%6%6%9%8%15%
1400
21st to endDay
410%7%10%11%5%7%8%8%7%23%
1282
March1st to 10thDay
313%6%11%11%6%8%7%7%7%24%
1800
11th to 20thDay
311%9%14%10%6%7%6%5%9%19%
1831
21st to endDay
311%7%13%10%47%6%6%6%26%
2376
April1st to 10thDay
412%7%14%11%6%7%6%6%7%21%
2214
11th to 20thDay
413%6%12%10%5%7%6%5%7%25%
2422
21st to endDay
6%13%6%10%8%5%7%6%6%7%26%
2560
May1st to 10thDay
11%15%6%11%8%46%5%6%7%22%
2739
11th to 20thDay
11%12%48%8%45%5%5%6%29%
2833
21st to endDay
10%9%37%7%47%6%7%8%32%
3257
June1st to 10thDay
14%9%5%8%9%47%7%6%7%25%
3132
11th to 20thDay
14%9%410%8%47%6%7%8%23%
3240
21st to endDay
11%8%49%9%5%7%7%7%9%24%
3240
July1st to 10thDay
12%7%38%8%46%7%9%9%27%
3240
11th to 20thDay
15%9%49%10%5%7%7%7%8%18%
2960
21st to endDay
13%7%49%7%46%7%7%8%28%
3135
August1st to 10thDay
10%6%48%8%5%5%6%6%8%33%
2822
11th to 20thDay
19%9%48%7%46%6%5%6%24%
2479
21st to endDay
20%10%48%7%46%5%6%8%22%
2732
September1st to 10thDay
18%12%5%9%8%46%5%5%7%21%
2239
11th to 20thDay
14%9%5%8%7%5%6%6%6%7%29%
2117
21st to endDay
18%13%412%9%5%45%5%6%19%
1976
October1st to 10thDay
13%13%5%10%10%5%6%5%5%6%21%
1752
11th to 20thDay
13%16%7%11%7%5%6%6%6%6%16%
1620
21st to endDay
11%15%6%13%9%5%7%7%6%6%17%
1600
November1st to 10thDay
8%17%8%15%11%6%6%6%6%6%10%
1302
11th to 20thDay
9%17%10%16%9%8%8%7%6%48%
1250
21st to endDay
7%17%10%14%9%6%8%7%6%7%9%
969
December1st to 10thDay
8%16%7%15%11%7%9%6%6%8%9%
950
11th to 20thDay
415%7%12%12%7%9%6%8%9%11%
1124
21st to endDay
10%16%7%12%11%6%9%8%7%7%8%
1386
January1st to 10thNight
7%14%7%15%14%7%9%5%5%5%12%
3249
11th to 20thNight
10%19%8%14%11%6%6%5%5%5%11%
2934
21st to endNight
9%15%8%13%10%6%7%6%6%6%14%
3168
February1st to 10thNight
6%14%6%13%8%5%8%7%6%6%21%
2643
11th to 20thNight
5%14%7%13%13%6%7%6%6%7%16%
2447
21st to endNight
311%6%11%10%5%5%5%6%8%30%
1971
March1st to 10thNight
312%7%11%10%5%5%5%5%6%31%
2160
11th to 20thNight
313%9%16%10%5%7%6%5%7%20%
2126
21st to endNight
412%8%12%10%5%7%6%6%6%25%
1980
April1st to 10thNight
5%11%6%11%8%5%7%7%7%7%26%
1746
11th to 20thNight
5%11%5%8%8%5%5%8%7%9%29%
1484
21st to endNight
8%14%6%9%8%46%5%7%8%27%
1400
May1st to 10thNight
10%10%47%7%46%8%9%9%26%
1220
11th to 20thNight
8%9%47%6%45%6%7%7%36%
1062
21st to endNight
8%7%46%7%5%6%6%6%9%35%
1018
June1st to 10thNight
11%6%37%7%6%7%7%7%9%30%
826
11th to 20thNight
14%7%28%7%5%5%6%5%8%33%
720
21st to endNight
9%6%37%7%46%8%8%10%30%
720
July1st to 10thNight
9%8%36%7%5%7%7%8%10%32%
720
11th to 20thNight
14%8%39%10%47%7%9%9%20%
997
21st to endNight
12%9%37%7%47%6%7%7%30%
1182
August1st to 10thNight
11%7%47%6%45%6%10%10%31%
1117
11th to 20thNight
15%8%47%8%45%5%8%10%27%
1419
21st to endNight
18%12%410%7%46%6%5%5%24%
1624
September1st to 10thNight
15%11%49%8%46%6%6%6%25%
1718
11th to 20thNight
11%9%47%8%45%6%5%7%34%
1843
21st to endNight
18%14%410%8%5%5%45%7%20%
1983
October1st to 10thNight
15%13%5%8%6%35%5%7%7%26%
2208
11th to 20thNight
16%19%5%10%8%35%45%7%19%
2340
21st to endNight
10%18%5%11%8%6%7%5%5%6%20%
2754
November1st to 10thNight
9%17%7%13%11%7%7%6%6%6%12%
2776
11th to 20thNight
8%17%8%16%10%6%6%6%7%6%9%
2928
21st to endNight
8%17%8%15%12%6%8%6%5%7%8%
3192
December1st to 10thNight
8%17%8%16%13%7%7%6%6%5%7%
3230
11th to 20thNight
5%16%8%15%13%7%6%5%6%7%12%
4063
21st to endNight
9%16%6%11%10%7%9%7%6%6%12%
6270

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
72%5%9%7%6%1
930
11th to 20thDay
74%8%7%5%6%
1098
21st to endDay
67%7%12%9%5%
1188
February1st to 10thDay
55%9%8%16%10%2
1316
11th to 20thDay
60%11%13%10%6%
1408
21st to endDay
52%10%17%16%6%
1282
March1st to 10thDay
56%10%10%16%7%1
1800
11th to 20thDay
60%10%13%12%5%
1831
21st to endDay
56%10%17%9%7%1
2376
April1st to 10thDay
61%10%14%11%4
2214
11th to 20thDay
56%11%13%16%4
2422
21st to endDay
56%11%16%13%5%
2560
May1st to 10thDay
61%9%14%13%3
2739
11th to 20thDay
51%9%14%18%7%
2836
21st to endDay
47%10%16%20%6%
3258
June1st to 10thDay
56%11%12%16%41
3132
11th to 20thDay
56%11%13%16%3
3240
21st to endDay
53%13%17%13%31
3240
July1st to 10thDay
49%12%19%16%4
3151
11th to 20thDay
59%15%18%8%
2867
21st to endDay
51%14%19%14%2
2961
August1st to 10thDay
47%13%22%16%2
2803
11th to 20thDay
58%12%16%12%1
2479
21st to endDay
59%13%17%10%1
2732
September1st to 10thDay
61%13%10%13%3
2239
11th to 20thDay
52%11%15%19%3
2117
21st to endDay
65%10%12%11%2
1976
October1st to 10thDay
62%10%14%11%2
1752
11th to 20thDay
64%10%14%11%1
1620
21st to endDay
63%10%14%11%2
1600
November1st to 10thDay
70%8%11%9%2
1302
11th to 20thDay
72%8%10%9%1
1250
21st to endDay
68%8%13%7%4
969
December1st to 10thDay
70%9%11%6%3
950
11th to 20thDay
62%6%14%10%7%
1126
21st to endDay
66%7%9%12%7%
1386
January1st to 10thNight
70%8%9%6%6%
3249
11th to 20thNight
72%7%10%7%5%
2934
21st to endNight
67%8%10%10%4
3168
February1st to 10thNight
59%9%8%15%8%1
2643
11th to 20thNight
63%9%12%11%5%
2450
21st to endNight
50%8%18%16%7%1
1971
March1st to 10thNight
54%7%12%18%7%2
2160
11th to 20thNight
61%9%12%12%6%
2128
21st to endNight
56%9%16%12%7%
1980
April1st to 10thNight
53%10%15%18%4
1746
11th to 20thNight
47%11%16%20%6%
1484
21st to endNight
54%9%17%14%5%
1400
May1st to 10thNight
50%11%19%17%3
1220
11th to 20thNight
44%9%15%24%8%1
1062
21st to endNight
43%10%14%25%7%
1018
June1st to 10thNight
49%10%15%22%31
826
11th to 20thNight
46%12%17%21%4
720
21st to endNight
45%12%22%19%2
720
July1st to 10thNight
44%12%19%20%41
700
11th to 20thNight
53%15%19%13%
967
21st to endNight
48%15%17%18%2
1116
August1st to 10thNight
44%15%22%17%3
1111
11th to 20thNight
50%15%16%17%3
1419
21st to endNight
61%11%15%13%
1624
September1st to 10thNight
56%12%16%14%1
1718
11th to 20thNight
47%12%16%21%4
1843
21st to endNight
64%10%11%13%3
1983
October1st to 10thNight
55%11%16%14%4
2208
11th to 20thNight
63%11%13%11%2
2340
21st to endNight
62%11%14%11%2
2754
November1st to 10thNight
67%9%12%10%1
2776
11th to 20thNight
70%10%10%9%1
2928
21st to endNight
70%8%10%9%3
3192
December1st to 10thNight
75%7%8%8%2
3230
11th to 20thNight
68%7%10%10%5%
4060
21st to endNight
62%8%9%10%9%1
6270

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
6%416%34%32%8%
151
11th to 20thDay
14%8%14%28%27%8%
166
21st to endDay
15%16%16%21%24%7%
176
February1st to 10thDay
13%421%36%21%5%
304
11th to 20thDay
11%13%24%29%16%7%
335
21st to endDay
8%9%27%30%19%8%
280
March1st to 10thDay
7%10%25%30%19%9%
340
11th to 20thDay
8%12%31%25%21%4
354
21st to endDay
8%13%25%27%20%7%
462
April1st to 10thDay
11%15%28%25%18%4
420
11th to 20thDay
10%14%27%25%20%5%
526
21st to endDay
14%15%30%25%13%3
600
May1st to 10thDay
19%17%24%24%12%3
603
11th to 20thDay
17%13%24%27%11%8%
625
21st to endDay
12%12%23%26%21%6%
826
June1st to 10thDay
17%9%21%25%21%7%
810
11th to 20thDay
17%7%22%28%21%5%
810
21st to endDay
12%9%20%29%22%7%
810
July1st to 10thDay
14%9%17%30%23%7%
796
11th to 20thDay
20%9%18%25%20%9%
689
21st to endDay
17%9%19%22%23%11%
684
August1st to 10thDay
14%7%20%29%19%11%
626
11th to 20thDay
25%17%18%23%12%5%
615
21st to endDay
24%11%21%23%17%4
653
September1st to 10thDay
22%14%24%21%15%4
450
11th to 20thDay
15%13%22%21%21%8%
450
21st to endDay
24%18%22%21%11%3
448
October1st to 10thDay
22%16%27%24%8%3
360
11th to 20thDay
21%17%26%22%10%4
360
21st to endDay
15%9%23%35%14%4
342
November1st to 10thDay
16%9%26%28%17%3
180
11th to 20thDay
16%7%22%30%17%7%
180
21st to endDay
13%11%26%32%11%8%
180
December1st to 10thDay
11%7%21%33%19%8%
180
11th to 20thDay
17%8%19%24%23%10%
156
21st to endDay
7%8%18%34%20%12%
99
January1st to 10thNight
13%419%35%25%5%
1015
11th to 20thNight
16%7%22%31%19%5%
817
21st to endNight
15%10%22%30%20%3
880
February1st to 10thNight
12%6%20%40%19%4
800
11th to 20thNight
10%7%24%38%17%4
784
21st to endNight
7%5%24%38%21%4
644
March1st to 10thNight
7%7%24%36%21%6%
720
11th to 20thNight
6%8%24%35%24%3
719
21st to endNight
5%8%20%31%28%8%
594
April1st to 10thNight
8%6%18%31%31%5%
540
11th to 20thNight
8%6%18%34%27%6%
533
21st to endNight
11%8%18%31%26%5%
500
May1st to 10thNight
10%7%20%31%26%5%
360
11th to 20thNight
12%7%19%30%30%2
354
21st to endNight
10%7%19%31%31%2
389
June1st to 10thNight
13%323%34%24%3
286
11th to 20thNight
17%416%36%23%4
180
21st to endNight
10%7%18%33%31%2
180
July1st to 10thNight
13%415%35%31%2
175
11th to 20thNight
15%8%19%33%23%2
344
21st to endNight
15%420%29%27%6%
394
August1st to 10thNight
14%322%33%23%4
358
11th to 20thNight
20%9%20%31%17%4
529
21st to endNight
24%6%19%26%22%3
594
September1st to 10thNight
18%9%22%29%20%2
540
11th to 20thNight
16%7%17%30%26%4
583
21st to endNight
24%13%21%27%13%3
720
October1st to 10thNight
22%8%23%29%15%3
720
11th to 20thNight
27%9%23%27%13%2
720
21st to endNight
17%10%23%31%16%4
855
November1st to 10thNight
16%5%23%34%19%3
830
11th to 20thNight
14%8%19%32%23%4
850
21st to endNight
14%8%25%32%17%4
1002
December1st to 10thNight
16%7%21%34%20%2
1040
11th to 20thNight
13%6%19%37%19%6%
1040
21st to endNight
14%7%18%34%21%7%
1144
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Copyright 2024 Attilla Danko


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