Swan River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Swan River clear sky chart from 2005-11-05 to 2018-01-20.

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%
16611
11%
48203
7%
16573
41%
16573
19%
35015

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 15thNight
29%
970
9%
2910
5%
970
33%
970
13%
2261
January16th to endNight
23%
985
9%
2765
3%
985
28%
985
12%
2272
February1st to 15thNight
38%
875
10%
2464
5%
875
42%
875
18%
1856
February16th to endNight
38%
669
11%
1951
7%
669
41%
669
16%
1469
March1st to 15thNight
37%
720
12%
2160
7%
720
42%
720
17%
1579
March16th to endNight
42%
583
16%
2029
14%
583
49%
583
17%
1395
April1st to 15thNight
42%
539
15%
1747
13%
539
48%
539
22%
1148
April16th to endNight
38%
540
13%
1591
7%
540
42%
540
23%
1089
May1st to 15thNight
36%
540
10%
1395
5%
540
38%
540
21%
1032
May16th to endNight
40%
563
5%
1311
3%
561
42%
561
26%
955
June1st to 15thNight
42%
494
0%
1214
0%
494
42%
494
24%
884
June16th to endNight
50%
360
0%
1080
0%
360
50%
360
21%
757
July1st to 15thNight
52%
412
0%
1092
0%
412
52%
412
35%
683
July16th to endNight
59%
564
6%
1315
4%
531
60%
531
40%
820
August1st to 15thNight
59%
539
12%
1432
6%
536
62%
536
37%
866
August16th to endNight
57%
573
18%
1687
14%
573
61%
573
36%
961
September1st to 15thNight
53%
540
16%
1817
18%
540
58%
540
29%
1074
September16th to endNight
46%
537
20%
1980
20%
537
54%
537
24%
1205
October1st to 15thNight
36%
708
15%
2148
10%
708
41%
708
20%
1515
October16th to endNight
31%
960
15%
2496
7%
960
35%
960
19%
1858
November1st to 15thNight
26%
950
10%
2649
4%
950
31%
950
13%
2102
November16th to endNight
25%
975
8%
2925
4%
975
29%
975
12%
2328
December1st to 15thNight
25%
975
6%
2925
3%
975
28%
975
9%
2436
December16th to endNight
29%
1040
11%
3120
6%
1040
34%
1040
11%
2470

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
13%8%46%6%35%5%5%7%33%
49349
Night
11%10%47%6%35%5%5%6%32%
48350
Cloud CoverDay
13%8%36%6%35%5%5%7%33%
49358
Night
11%10%47%6%35%45%6%32%
48354
Cloud CoverDay
12%8%46%6%35%5%5%7%33%
49359
Night
10%10%47%7%35%5%5%6%32%
48355
TransparencyDay
48%8%15%20%6%
49013
Night
50%7%14%20%6%
48203
SeeingDay
17%8%28%26%14%3
6702
Night
15%6%29%32%14%1
16621

By Month

Percentage Cloud Cover NE (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 15thDay
7%11%6%8%9%5%7%6%7%6%23%
1358
16th to endDay
8%15%6%7%8%5%7%45%6%23%
1560
February1st to 15thDay
6%7%38%8%5%9%8%7%7%27%
1400
16th to endDay
7%9%6%12%8%5%8%6%5%6%23%
1532
March1st to 15thDay
11%9%5%9%7%345%6%7%29%
1790
16th to endDay
9%11%49%7%445%5%7%30%
2195
April1st to 15thDay
10%8%5%7%7%25%5%5%7%33%
2201
16th to endDay
12%8%36%445%5%6%6%36%
2367
May1st to 15thDay
16%10%35%5%35%446%33%
2556
16th to endDay
19%6%35%5%3446%7%34%
2803
June1st to 15thDay
21%7%25%5%34447%31%
2743
16th to endDay
16%6%26%6%46%5%5%7%30%
2880
July1st to 15thDay
12%5%245%35%5%6%8%40%
2799
16th to endDay
10%4245%35%5%6%9%42%
2762
August1st to 15thDay
12%5%25%5%35%5%7%9%38%
2520
16th to endDay
13%6%245%3446%8%42%
2515
September1st to 15thDay
13%7%35%43345%7%42%
2142
16th to endDay
13%6%35%434448%41%
1980
October1st to 15thDay
18%11%36%433336%35%
1797
16th to endDay
16%12%5%7%6%24445%29%
1728
November1st to 15thDay
14%16%6%9%6%3343426%
1535
16th to endDay
9%13%7%10%8%345%47%25%
1365
December1st to 15thDay
10%12%5%9%11%5%6%7%5%5%20%
1365
16th to endDay
6%12%8%12%9%45%5%6%6%21%
1456
January1st to 15thNight
7%12%7%9%8%47%7%5%5%22%
2910
16th to endNight
7%13%7%10%9%5%7%5%6%6%18%
2765
February1st to 15thNight
8%9%48%7%5%10%5%5%6%28%
2460
16th to endNight
5%11%7%12%8%46%5%5%5%26%
1951
March1st to 15thNight
10%11%5%7%7%45%5%5%6%30%
2147
16th to endNight
8%9%47%6%46%5%5%7%33%
2029
April1st to 15thNight
9%7%46%6%35%46%6%38%
1747
16th to endNight
14%6%27%5%245%5%6%37%
1591
May1st to 15thNight
14%11%47%5%24435%35%
1395
16th to endNight
20%6%23425%45%6%38%
1310
June1st to 15thNight
18%7%25%4245%5%7%35%
1214
16th to endNight
13%5%35%6%45%6%5%6%37%
1080
July1st to 15thNight
9%42432336%9%48%
1158
16th to endNight
7%32343346%7%52%
1406
August1st to 15thNight
10%32232446%7%52%
1440
16th to endNight
10%423323448%53%
1687
September1st to 15thNight
10%5%244235%46%49%
1817
16th to endNight
14%6%23423446%45%
1980
October1st to 15thNight
16%11%45%423345%36%
2148
16th to endNight
13%14%37%5%24435%33%
2496
November1st to 15thNight
13%14%6%9%7%34445%25%
2649
16th to endNight
11%12%6%11%8%46%445%23%
2925
December1st to 15thNight
9%14%6%11%12%5%6%6%5%6%16%
2925
16th to endNight
8%13%7%12%9%45%5%5%6%20%
3120

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 15thDay
8%11%6%8%8%46%7%7%6%23%
1359
16th to endDay
10%15%6%8%7%46%46%6%23%
1560
February1st to 15thDay
6%7%5%8%7%5%9%7%7%8%27%
1400
16th to endDay
8%9%6%11%9%5%7%5%5%6%23%
1532
March1st to 15thDay
11%9%49%7%3446%8%29%
1800
16th to endDay
10%11%49%6%35%5%5%7%31%
2193
April1st to 15thDay
10%8%47%7%345%5%7%33%
2201
16th to endDay
13%8%36%435%5%5%6%37%
2367
May1st to 15thDay
17%10%25%43445%6%34%
2556
16th to endDay
20%5%25%5%245%6%6%34%
2803
June1st to 15thDay
22%6%25%5%345%5%7%31%
2743
16th to endDay
17%5%26%6%36%5%6%7%31%
2880
July1st to 15thDay
13%5%24435%5%6%8%40%
2799
16th to endDay
11%414425%5%7%8%43%
2762
August1st to 15thDay
13%425%5%346%6%8%40%
2520
16th to endDay
14%5%1443435%8%43%
2515
September1st to 15thDay
14%7%2442345%7%43%
2142
16th to endDay
14%6%24434448%42%
1980
October1st to 15thDay
19%12%25%424335%35%
1797
16th to endDay
16%12%5%6%6%24446%29%
1728
November1st to 15thDay
15%17%6%8%6%23335%26%
1535
16th to endDay
10%13%7%11%7%25%447%25%
1365
December1st to 15thDay
10%11%5%9%11%6%6%7%5%5%20%
1365
16th to endDay
7%12%8%12%9%445%5%8%21%
1456
January1st to 15thNight
7%12%7%10%9%46%6%6%5%22%
2910
16th to endNight
8%15%7%9%8%5%7%6%5%6%18%
2765
February1st to 15thNight
8%9%39%7%5%9%5%5%6%28%
2453
16th to endNight
6%12%6%12%8%45%446%27%
1951
March1st to 15thNight
11%11%5%7%7%45%45%7%30%
2160
16th to endNight
9%9%5%6%6%46%5%6%7%33%
2027
April1st to 15thNight
9%7%37%5%345%6%6%39%
1747
16th to endNight
15%6%36%5%345%47%36%
1591
May1st to 15thNight
15%10%37%5%3445%5%35%
1394
16th to endNight
21%5%2333435%7%38%
1311
June1st to 15thNight
20%6%244345%5%6%36%
1214
16th to endNight
15%5%346%36%45%6%37%
1080
July1st to 15thNight
10%41333346%8%50%
1158
16th to endNight
8%32332446%8%53%
1406
August1st to 15thNight
10%31332345%7%53%
1440
16th to endNight
11%41231345%7%54%
1687
September1st to 15thNight
11%5%135%23446%49%
1817
16th to endNight
15%6%24423446%46%
1980
October1st to 15thNight
17%11%35%423445%36%
2148
16th to endNight
15%13%46%5%2444434%
2496
November1st to 15thNight
14%14%6%8%6%34345%26%
2649
16th to endNight
11%13%6%10%8%35%446%23%
2925
December1st to 15thNight
10%14%6%10%11%5%6%6%46%17%
2925
16th to endNight
8%13%7%12%9%45%5%5%6%21%
3120

Percentage Cloud Cover SW (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 15thDay
7%10%6%8%8%46%6%7%7%23%
1358
16th to endDay
9%15%5%8%8%47%5%6%6%23%
1560
February1st to 15thDay
5%8%38%9%5%9%7%7%8%27%
1400
16th to endDay
7%10%6%12%8%5%7%6%6%6%23%
1532
March1st to 15thDay
11%10%49%7%345%6%8%28%
1800
16th to endDay
9%11%49%6%46%5%5%7%30%
2195
April1st to 15thDay
10%8%5%7%7%345%6%7%32%
2201
16th to endDay
11%8%35%5%45%6%6%6%36%
2367
May1st to 15thDay
16%10%35%5%35%45%6%33%
2556
16th to endDay
19%6%35%5%3446%7%34%
2803
June1st to 15thDay
21%7%35%5%35%5%47%31%
2743
16th to endDay
16%6%36%6%46%5%6%7%30%
2880
July1st to 15thDay
11%5%25%5%35%5%6%9%39%
2799
16th to endDay
9%425%5%345%7%9%42%
2762
August1st to 15thDay
11%5%245%345%6%10%38%
2520
16th to endDay
12%5%2443446%8%42%
2515
September1st to 15thDay
12%7%25%43345%7%42%
2142
16th to endDay
12%6%25%434448%41%
1980
October1st to 15thDay
17%11%36%434346%35%
1797
16th to endDay
15%12%47%6%35%5%45%29%
1728
November1st to 15thDay
14%16%6%8%7%3343426%
1535
16th to endDay
9%13%7%9%8%345%47%25%
1365
December1st to 15thDay
9%11%6%9%10%5%6%7%5%5%21%
1365
16th to endDay
6%13%7%11%9%45%5%6%7%21%
1456
January1st to 15thNight
6%12%7%10%9%47%7%6%6%22%
2910
16th to endNight
8%14%7%10%9%5%7%5%6%6%18%
2765
February1st to 15thNight
8%9%47%7%5%10%6%46%28%
2453
16th to endNight
5%11%7%11%8%46%5%5%6%26%
1951
March1st to 15thNight
10%11%5%7%7%45%45%6%30%
2160
16th to endNight
7%10%47%6%45%6%6%7%32%
2029
April1st to 15thNight
8%7%46%7%345%6%6%38%
1747
16th to endNight
14%6%37%5%345%5%7%36%
1591
May1st to 15thNight
14%10%5%6%5%34445%35%
1394
16th to endNight
20%5%24335%45%7%37%
1310
June1st to 15thNight
19%7%245%3445%7%35%
1214
16th to endNight
13%5%26%6%35%6%5%6%37%
1080
July1st to 15thNight
8%42442446%9%49%
1158
16th to endNight
7%32342447%7%52%
1406
August1st to 15thNight
9%41332446%7%52%
1440
16th to endNight
10%423313448%53%
1687
September1st to 15thNight
10%5%144235%46%49%
1817
16th to endNight
14%6%245%23446%45%
1980
October1st to 15thNight
16%10%46%424445%35%
2148
16th to endNight
13%13%46%6%34445%33%
2496
November1st to 15thNight
13%14%6%9%6%35%44426%
2649
16th to endNight
11%13%6%10%8%46%5%46%23%
2925
December1st to 15thNight
9%14%5%11%12%47%5%5%6%16%
2925
16th to endNight
8%13%7%11%9%5%5%5%6%6%20%
3120

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 15thDay
54%9%11%20%4
1359
16th to endDay
58%7%9%18%5%
1560
February1st to 15thDay
49%11%16%16%5%
1400
16th to endDay
58%6%10%18%5%
1532
March1st to 15thDay
51%7%14%20%5%
1800
16th to endDay
53%7%15%18%5%
2195
April1st to 15thDay
48%7%15%18%9%
2201
16th to endDay
44%7%15%19%11%1
2367
May1st to 15thDay
50%5%11%22%8%1
2556
16th to endDay
47%8%10%21%10%1
2807
June1st to 15thDay
52%6%12%20%7%
2743
16th to endDay
50%10%16%18%4
2880
July1st to 15thDay
38%9%18%26%6%
2636
16th to endDay
38%8%20%26%5%
2590
August1st to 15thDay
38%11%22%22%4
2504
16th to endDay
37%8%20%26%6%
2515
September1st to 15thDay
39%8%17%26%6%1
2142
16th to endDay
41%7%15%25%9%
1980
October1st to 15thDay
51%6%14%22%5%
1797
16th to endDay
55%7%13%17%4
1728
November1st to 15thDay
61%6%11%14%6%
1535
16th to endDay
57%8%16%13%3
1365
December1st to 15thDay
61%9%13%12%3
1365
16th to endDay
58%9%13%15%3
1456
January1st to 15thNight
57%8%12%15%5%
2910
16th to endNight
62%9%11%11%5%
2765
February1st to 15thNight
52%8%14%16%7%
2464
16th to endNight
56%5%13%18%6%
1951
March1st to 15thNight
53%6%14%20%41
2160
16th to endNight
48%7%13%23%7%
2029
April1st to 15thNight
44%6%12%21%11%3
1747
16th to endNight
45%6%14%19%11%2
1591
May1st to 15thNight
51%6%7%19%14%1
1395
16th to endNight
45%7%11%19%14%
1311
June1st to 15thNight
48%6%12%21%10%1
1214
16th to endNight
45%9%20%18%5%
1080
July1st to 15thNight
31%9%18%31%9%
1092
16th to endNight
28%8%23%32%6%
1315
August1st to 15thNight
28%8%23%31%7%
1432
16th to endNight
29%5%20%33%9%
1687
September1st to 15thNight
33%7%15%32%9%1
1817
16th to endNight
39%6%13%29%10%
1980
October1st to 15thNight
49%6%14%26%3
2148
16th to endNight
52%6%13%21%6%
2496
November1st to 15thNight
59%8%12%13%41
2649
16th to endNight
60%8%15%13%2
2925
December1st to 15thNight
65%9%10%12%2
2925
16th to endNight
61%7%11%14%4
3120

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 15thDay
7%239%37%13%
135
16th to endDay
19%340%28%7%
109
February1st to 15thDay
11%138%36%12%
90
16th to endDay
17%432%29%16%
81
March1st to 15thDay
22%422%38%10%2
90
16th to endDay
20%12%27%22%12%3
186
April1st to 15thDay
15%10%36%27%9%
320
16th to endDay
14%10%30%27%15%2
450
May1st to 15thDay
22%10%29%25%9%1
468
16th to endDay
17%12%26%23%17%2
517
June1st to 15thDay
22%9%30%22%10%4
495
16th to endDay
20%7%26%24%14%6%
495
July1st to 15thDay
16%6%22%27%21%5%
475
16th to endDay
9%8%26%26%20%7%
515
August1st to 15thDay
16%7%20%24%23%7%
493
16th to endDay
14%5%23%30%21%4
523
September1st to 15thDay
20%11%36%22%7%1
297
16th to endDay
18%10%27%23%17%2
135
October1st to 15thDay
31%7%31%21%7%1
135
16th to endDay
30%427%26%9%
144
November1st to 15thDay
21%8%35%24%7%2
135
16th to endDay
28%5%32%22%11%
135
December1st to 15thDay
17%136%34%8%1
135
16th to endDay
11%226%41%15%2
144
January1st to 15thNight
12%6%35%31%12%1
975
16th to endNight
15%8%39%27%9%1
985
February1st to 15thNight
10%431%35%15%1
880
16th to endNight
10%5%26%37%17%1
669
March1st to 15thNight
15%6%27%36%12%1
720
16th to endNight
11%7%28%28%19%3
583
April1st to 15thNight
12%430%33%16%2
539
16th to endNight
16%6%30%32%12%1
540
May1st to 15thNight
19%8%29%30%10%
540
16th to endNight
22%8%24%30%13%
563
June1st to 15thNight
21%427%31%14%
494
16th to endNight
16%420%37%19%1
360
July1st to 15thNight
10%426%36%19%1
412
16th to endNight
8%225%38%21%3
564
August1st to 15thNight
12%320%33%25%3
539
16th to endNight
13%222%39%20%1
573
September1st to 15thNight
13%5%22%38%19%
540
16th to endNight
16%425%38%12%1
537
October1st to 15thNight
23%7%27%31%9%1
708
16th to endNight
22%7%28%31%9%
960
November1st to 15thNight
20%8%32%26%11%1
950
16th to endNight
17%7%34%29%8%1
975
December1st to 15thNight
15%5%32%29%13%3
975
16th to endNight
14%6%27%32%15%3
1040
Page generated at 2018-01-21 11:19:23. Version ac04

Copyright 2018 A. Danko


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