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 2017-09-20.

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%
16036
11%
46511
7%
15998
41%
15998
19%
33783

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
30%
895
8%
2685
6%
895
33%
895
12%
2091
January16th to endNight
22%
960
9%
2695
2%
960
28%
960
12%
2218
February1st to 15thNight
38%
875
10%
2464
5%
875
43%
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
41%
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
35%
540
10%
1395
5%
540
38%
540
21%
1032
May16th to endNight
39%
563
5%
1311
3%
561
41%
561
26%
955
June1st to 15thNight
42%
494
0%
1214
0%
494
42%
494
24%
884
June16th to endNight
51%
360
0%
1080
0%
360
51%
360
21%
757
July1st to 15thNight
52%
412
0%
1092
0%
412
52%
412
35%
683
July16th to endNight
58%
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
54%
540
16%
1817
18%
540
58%
540
29%
1074
September16th to endNight
45%
507
19%
1870
19%
507
52%
507
23%
1149
October1st to 15thNight
35%
648
16%
1968
10%
648
41%
648
19%
1396
October16th to endNight
31%
880
14%
2288
7%
880
35%
880
19%
1712
November1st to 15thNight
26%
875
11%
2440
4%
875
32%
875
14%
1924
November16th to endNight
26%
900
8%
2700
4%
900
30%
900
12%
2148
December1st to 15thNight
26%
900
6%
2700
4%
900
29%
900
9%
2259
December16th to endNight
27%
960
10%
2880
5%
960
32%
960
10%
2318

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%
48354
Night
11%10%47%6%35%5%5%6%32%
46658
Cloud CoverDay
14%8%36%6%35%5%5%7%33%
48363
Night
12%10%47%6%35%45%6%32%
46662
Cloud CoverDay
12%8%46%6%35%5%5%7%33%
48364
Night
11%10%47%7%35%5%5%6%32%
46663
TransparencyDay
48%8%15%20%6%
48018
Night
50%7%14%20%6%
46511
SeeingDay
18%8%28%26%15%3
6335
Night
15%6%29%32%14%1
16046

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
8%11%6%8%8%5%7%7%7%6%23%
1253
16th to endDay
9%15%6%7%8%5%7%5%5%6%23%
1527
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%
1859
October1st to 15thDay
18%11%46%433335%33%
1648
16th to endDay
16%12%5%7%7%25%44428%
1584
November1st to 15thDay
15%16%5%8%6%33435%26%
1414
16th to endDay
9%13%7%10%8%35%5%47%24%
1260
December1st to 15thDay
10%12%49%11%6%6%7%5%5%19%
1260
16th to endDay
7%13%9%13%9%3446%6%20%
1344
January1st to 15thNight
7%13%7%9%9%5%7%6%5%6%22%
2685
16th to endNight
8%13%7%10%9%5%7%5%6%6%18%
2695
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
15%6%23423446%44%
1870
October1st to 15thNight
17%12%45%5%23345%35%
1968
16th to endNight
14%14%38%5%34435%33%
2288
November1st to 15thNight
14%14%6%8%7%34445%26%
2440
16th to endNight
12%12%6%11%8%36%445%23%
2700
December1st to 15thNight
9%13%6%11%12%5%7%6%5%6%16%
2700
16th to endNight
8%14%8%12%9%45%5%5%6%19%
2880

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%9%8%46%7%7%6%23%
1254
16th to endDay
10%14%6%8%7%46%46%6%23%
1527
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%2443445%8%42%
1859
October1st to 15thDay
19%12%26%424335%34%
1648
16th to endDay
17%12%5%6%6%25%445%27%
1584
November1st to 15thDay
16%17%6%7%6%23435%27%
1414
16th to endDay
10%13%8%11%7%35%45%7%25%
1260
December1st to 15thDay
11%12%5%9%11%6%6%7%45%19%
1260
16th to endDay
7%13%9%13%8%4445%8%20%
1344
January1st to 15thNight
7%13%7%9%9%46%5%6%5%22%
2685
16th to endNight
8%15%7%9%8%5%7%6%5%6%18%
2695
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
16%6%14413446%45%
1870
October1st to 15thNight
18%12%45%423335%36%
1968
16th to endNight
15%13%46%5%2443434%
2288
November1st to 15thNight
14%14%6%7%6%44445%27%
2440
16th to endNight
12%13%7%10%8%34446%23%
2700
December1st to 15thNight
10%13%6%11%12%5%6%6%46%16%
2700
16th to endNight
9%14%7%13%8%45%45%6%20%
2880

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
8%10%7%8%8%5%6%6%7%7%23%
1253
16th to endDay
9%14%5%7%8%47%5%6%6%23%
1527
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
13%6%25%43445%8%41%
1859
October1st to 15thDay
18%11%37%434345%33%
1648
16th to endDay
15%12%5%7%6%35%5%45%28%
1584
November1st to 15thDay
15%15%5%7%7%3443427%
1414
16th to endDay
9%13%7%9%9%35%5%5%7%24%
1260
December1st to 15thDay
10%12%5%9%10%5%6%7%5%5%20%
1260
16th to endDay
6%14%8%12%9%345%6%7%20%
1344
January1st to 15thNight
6%13%7%9%9%47%6%6%6%22%
2685
16th to endNight
8%13%7%10%9%5%7%5%6%6%18%
2695
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%24446%44%
1870
October1st to 15thNight
17%10%47%424445%35%
1968
16th to endNight
14%13%46%6%3443433%
2288
November1st to 15thNight
13%13%6%8%6%35%44427%
2440
16th to endNight
11%13%6%10%8%45%5%46%23%
2700
December1st to 15thNight
9%13%6%11%13%47%5%5%6%16%
2700
16th to endNight
8%14%8%11%9%5%5%5%6%6%19%
2880

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%10%11%20%3
1254
16th to endDay
58%7%9%18%5%
1527
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%
1859
October1st to 15thDay
53%6%14%20%5%
1648
16th to endDay
57%7%13%17%3
1584
November1st to 15thDay
60%6%11%14%6%
1414
16th to endDay
58%8%16%13%3
1260
December1st to 15thDay
62%9%13%12%2
1260
16th to endDay
59%9%13%15%2
1344
January1st to 15thNight
58%8%12%15%4
2685
16th to endNight
62%9%11%11%4
2695
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%7%13%28%10%
1870
October1st to 15thNight
50%6%13%25%3
1968
16th to endNight
53%6%13%21%5%
2288
November1st to 15thNight
58%7%12%14%5%1
2440
16th to endNight
61%7%15%13%2
2700
December1st to 15thNight
65%9%10%12%1
2700
16th to endNight
62%8%11%14%3
2880

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%37%36%17%
90
16th to endDay
19%339%28%8%1
96
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
20%11%27%19%18%1
102
October1st to 15thDay
35%5%28%20%7%2
90
16th to endDay
35%122%26%13%1
96
November1st to 15thDay
22%12%35%21%7%1
90
16th to endDay
32%323%24%16%
90
December1st to 15thDay
21%230%32%12%2
90
16th to endDay
17%226%32%18%3
96
January1st to 15thNight
12%7%34%31%12%1
900
16th to endNight
14%8%39%27%9%1
960
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%426%38%12%1
507
October1st to 15thNight
24%7%26%30%9%1
648
16th to endNight
22%7%28%30%9%1
880
November1st to 15thNight
20%7%33%25%11%1
875
16th to endNight
18%7%33%30%9%1
900
December1st to 15thNight
14%6%31%29%14%4
900
16th to endNight
15%6%27%31%15%3
960
Page generated at 2017-09-21 06:18:19. Version ac04

Copyright 2017 A. Danko


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