Sparwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sparwood clear sky chart from 2005-11-06 to 2024-01-15.

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
31%
23369
10%
74940
7%
23324
34%
23324
14%
55466

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
14%
950
4%
2836
1%
946
17%
946
5%
2491
January11th to 20thNight
15%
801
8%
2641
5%
801
19%
801
7%
2223
January21st to endNight
16%
792
6%
2772
4%
792
19%
792
7%
2305
February1st to 10thNight
17%
720
7%
2520
5%
720
21%
720
8%
2060
February11th to 20thNight
16%
704
8%
2258
4%
700
21%
700
10%
1812
February21st to endNight
26%
592
11%
1776
7%
592
31%
592
11%
1396
March1st to 10thNight
21%
720
7%
2160
4%
720
25%
720
11%
1734
March11th to 20thNight
33%
720
11%
2030
7%
720
36%
720
15%
1562
March21st to endNight
29%
792
6%
2114
2%
792
31%
792
14%
1662
April1st to 10thNight
34%
716
9%
1796
3%
716
38%
716
18%
1369
April11th to 20thNight
30%
533
12%
1601
7%
533
33%
533
16%
1170
April21st to endNight
32%
540
10%
1620
7%
540
35%
540
16%
1161
May1st to 10thNight
38%
461
8%
1541
9%
461
40%
461
18%
1057
May11th to 20thNight
50%
354
10%
1300
14%
354
51%
354
20%
812
May21st to endNight
40%
388
6%
1358
6%
388
42%
388
15%
980
June1st to 10thNight
42%
360
4%
1260
2%
360
43%
360
17%
877
June11th to 20thNight
36%
360
3%
1260
0%
360
37%
360
15%
898
June21st to endNight
53%
360
6%
1260
2%
360
55%
360
27%
723
July1st to 10thNight
65%
350
9%
1225
4%
350
67%
350
39%
603
July11th to 20thNight
58%
348
15%
1218
14%
348
63%
348
36%
608
July21st to endNight
64%
394
20%
1475
25%
372
73%
372
40%
659
August1st to 10thNight
65%
358
21%
1424
27%
356
72%
356
33%
693
August11th to 20thNight
63%
508
25%
1576
21%
508
67%
508
44%
798
August21st to endNight
52%
594
26%
1782
19%
594
56%
594
37%
981
September1st to 10thNight
51%
695
21%
1775
11%
695
55%
695
39%
1045
September11th to 20thNight
50%
720
19%
1973
12%
720
54%
720
31%
1246
September21st to endNight
41%
720
16%
1980
11%
720
45%
720
26%
1302
October1st to 10thNight
41%
720
15%
2016
11%
720
45%
720
23%
1363
October11th to 20thNight
37%
720
13%
2313
9%
720
42%
720
18%
1587
October21st to endNight
27%
792
10%
2574
6%
792
33%
792
12%
1968
November1st to 10thNight
19%
749
8%
2414
5%
749
22%
749
9%
1959
November11th to 20thNight
16%
950
8%
2714
3%
950
21%
950
9%
2232
November21st to endNight
19%
950
5%
2850
2%
950
21%
950
9%
2333
December1st to 10thNight
17%
950
7%
2850
4%
950
20%
950
8%
2412
December11th to 20thNight
11%
950
2%
3506
1%
949
12%
949
4%
3145
December21st to endNight
12%
1038
4%
5172
2%
1026
16%
1026
4%
4240

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
8%13%5%9%7%45%5%6%7%30%
74615
Night
6%14%6%11%8%45%5%5%7%28%
75157
TransparencyDay
52%8%14%17%8%1
74307
Night
54%8%13%16%7%1
74983
SeeingDay
20%21%30%19%9%2
14092
Night
15%14%32%27%11%1
23377

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
319%10%17%10%5%6%6%5%6%13%
1329
11th to 20thDay
317%8%15%9%47%47%8%19%
1424
21st to endDay
314%10%15%11%5%7%6%5%5%18%
1584
February1st to 10thDay
5%15%10%15%10%5%6%6%5%6%18%
1440
11th to 20thDay
317%10%15%10%47%5%5%7%17%
1584
21st to endDay
316%8%14%11%6%7%7%5%6%17%
1480
March1st to 10thDay
418%8%14%9%46%6%6%6%17%
1800
11th to 20thDay
7%22%8%10%7%35%5%5%5%23%
1929
21st to endDay
8%25%8%12%7%45%45%5%17%
2240
April1st to 10thDay
7%18%8%13%8%5%5%6%5%6%20%
2163
11th to 20thDay
9%20%7%10%7%45%5%5%6%21%
2310
21st to endDay
11%15%6%9%7%5%5%5%5%6%25%
2340
May1st to 10thDay
12%17%48%7%45%46%7%26%
2416
11th to 20thDay
13%12%48%7%46%6%6%7%28%
2590
21st to endDay
22%12%5%8%7%45%45%6%22%
2917
June1st to 10thDay
17%12%5%8%8%45%5%6%7%24%
2700
11th to 20thDay
18%11%38%8%5%7%7%7%6%20%
2700
21st to endDay
9%7%36%6%45%6%7%8%39%
2700
July1st to 10thDay
6%5%25%5%45%5%7%9%48%
2700
11th to 20thDay
6%4246%35%5%6%9%50%
2700
21st to endDay
42134345%6%8%60%
2752
August1st to 10thDay
5%424436%5%6%8%52%
2507
11th to 20thDay
6%4245%25%46%7%54%
2325
21st to endDay
7%6%245%45%5%5%9%48%
2574
September1st to 10thDay
9%8%35%44445%6%46%
2183
11th to 20thDay
10%7%36%5%446%6%8%42%
1986
21st to endDay
9%11%35%6%35%5%6%7%40%
1980
October1st to 10thDay
10%13%49%6%35%5%7%7%32%
1944
11th to 20thDay
6%15%37%8%35%5%5%8%33%
1643
21st to endDay
8%18%6%8%6%45%5%6%7%28%
1782
November1st to 10thDay
11%21%7%12%8%45%445%20%
1646
11th to 20thDay
5%16%8%12%9%47%6%5%5%22%
1463
21st to endDay
6%15%9%14%10%4445%7%22%
1330
December1st to 10thDay
6%18%7%16%11%7%6%436%17%
1330
11th to 20thDay
422%9%19%11%46%445%12%
1682
21st to endDay
221%8%15%11%6%7%5%45%16%
2442
January1st to 10thNight
419%12%20%11%5%6%5%45%11%
2836
11th to 20thNight
319%8%20%11%45%5%45%14%
2641
21st to endNight
315%11%17%13%5%7%5%46%14%
2772
February1st to 10thNight
418%8%17%11%6%6%46%6%15%
2520
11th to 20thNight
319%10%15%8%45%45%7%20%
2257
21st to endNight
313%8%14%12%5%6%5%5%7%22%
1776
March1st to 10thNight
318%8%14%8%5%6%6%5%8%19%
2160
11th to 20thNight
6%19%6%9%6%35%5%6%7%27%
2030
21st to endNight
5%18%8%10%6%45%5%7%9%23%
2114
April1st to 10thNight
6%13%7%9%7%446%7%8%29%
1796
11th to 20thNight
7%16%5%9%6%45%5%5%7%30%
1601
21st to endNight
8%14%5%9%6%3446%7%34%
1620
May1st to 10thNight
8%16%47%6%345%49%33%
1541
11th to 20thNight
9%10%36%5%45%6%8%10%35%
1300
21st to endNight
18%10%47%6%35%46%6%30%
1358
June1st to 10thNight
13%9%46%5%35%7%6%9%32%
1260
11th to 20thNight
17%9%36%6%5%6%6%7%7%29%
1260
21st to endNight
6%425%5%35%6%8%7%47%
1260
July1st to 10thNight
43123345%7%9%57%
1260
11th to 20thNight
431343345%8%60%
1260
21st to endNight
221332446%7%65%
1562
August1st to 10thNight
34145%3436%8%59%
1432
11th to 20thNight
6%2133245%5%10%61%
1576
21st to endNight
7%5%233235%6%7%57%
1782
September1st to 10thNight
6%435%32445%7%56%
1775
11th to 20thNight
9%7%35%5%3336%9%48%
1973
21st to endNight
10%10%245%3346%9%43%
1980
October1st to 10thNight
11%10%37%4335%47%42%
2016
11th to 20thNight
7%12%47%5%46%5%6%7%35%
2313
21st to endNight
7%19%5%9%7%45%5%6%8%24%
2574
November1st to 10thNight
11%21%6%11%6%45%5%6%7%19%
2414
11th to 20thNight
419%10%14%10%445%5%6%19%
2714
21st to endNight
5%17%8%17%11%5%5%447%18%
2850
December1st to 10thNight
5%18%8%17%10%5%8%5%5%6%13%
2850
11th to 20thNight
222%9%19%14%6%6%445%8%
3510
21st to endNight
321%9%16%11%5%6%6%45%11%
5214

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
69%11%10%6%31
1329
11th to 20thDay
62%10%13%10%32
1424
21st to endDay
64%10%11%10%4
1584
February1st to 10thDay
65%8%13%8%5%1
1440
11th to 20thDay
65%9%12%10%4
1593
21st to endDay
64%8%11%10%6%1
1480
March1st to 10thDay
65%7%13%10%4
1800
11th to 20thDay
61%8%11%14%6%
1930
21st to endDay
69%8%12%7%4
2240
April1st to 10thDay
64%8%15%11%3
2163
11th to 20thDay
62%8%14%14%2
2310
21st to endDay
59%8%15%16%21
2340
May1st to 10thDay
56%8%16%15%4
2416
11th to 20thDay
53%8%16%17%5%
2594
21st to endDay
63%7%14%13%3
2918
June1st to 10thDay
59%7%14%15%5%
2700
11th to 20thDay
61%8%13%12%5%
2700
21st to endDay
41%9%17%22%11%1
2700
July1st to 10thDay
31%8%15%28%16%2
2626
11th to 20thDay
30%7%13%26%21%3
2619
21st to endDay
22%7%10%32%25%4
2599
August1st to 10thDay
29%8%14%28%17%4
2490
11th to 20thDay
27%7%17%31%15%1
2325
21st to endDay
32%8%15%27%17%2
2574
September1st to 10thDay
36%7%14%25%14%3
2183
11th to 20thDay
39%7%15%27%11%2
1986
21st to endDay
43%8%19%20%9%1
1980
October1st to 10thDay
49%8%16%19%7%
1944
11th to 20thDay
49%10%16%18%6%
1643
21st to endDay
54%10%16%15%6%
1782
November1st to 10thDay
66%9%11%10%31
1646
11th to 20thDay
60%11%15%9%4
1463
21st to endDay
60%10%14%10%6%
1330
December1st to 10thDay
67%6%10%10%5%1
1330
11th to 20thDay
72%9%9%7%2
1684
21st to endDay
62%11%7%12%7%1
2442
January1st to 10thNight
75%7%7%6%41
2836
11th to 20thNight
70%7%8%9%42
2641
21st to endNight
67%10%9%9%6%
2772
February1st to 10thNight
68%6%9%9%6%2
2520
11th to 20thNight
64%7%13%12%4
2258
21st to endNight
60%7%11%13%6%1
1776
March1st to 10thNight
63%7%14%12%4
2160
11th to 20thNight
55%9%15%15%6%
2030
21st to endNight
56%10%18%11%31
2114
April1st to 10thNight
50%10%18%15%7%
1796
11th to 20thNight
51%8%15%21%4
1601
21st to endNight
50%8%16%21%5%1
1620
May1st to 10thNight
48%7%20%18%7%
1541
11th to 20thNight
40%9%23%22%6%
1300
21st to endNight
53%8%16%19%4
1358
June1st to 10thNight
48%9%20%18%5%
1260
11th to 20thNight
51%8%18%15%7%
1260
21st to endNight
30%10%20%27%11%1
1260
July1st to 10thNight
20%9%23%32%14%3
1225
11th to 20thNight
22%8%15%29%21%5%
1218
21st to endNight
17%8%12%32%26%4
1475
August1st to 10thNight
24%8%14%31%19%4
1424
11th to 20thNight
20%6%17%39%16%1
1576
21st to endNight
25%7%15%34%18%1
1782
September1st to 10thNight
27%5%17%31%15%4
1775
11th to 20thNight
35%7%16%28%13%1
1973
21st to endNight
39%7%21%20%12%1
1980
October1st to 10thNight
42%8%16%25%9%1
2016
11th to 20thNight
45%9%18%21%6%1
2313
21st to endNight
57%9%14%15%5%
2574
November1st to 10thNight
64%9%11%11%41
2414
11th to 20thNight
63%9%10%12%5%
2714
21st to endNight
64%8%12%9%5%1
2850
December1st to 10thNight
70%7%8%10%41
2850
11th to 20thNight
76%10%9%5%2
3507
21st to endNight
66%11%9%6%6%1
5214

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
20%22%30%16%8%4
180
11th to 20thDay
17%20%35%22%42
168
21st to endDay
14%23%44%11%6%3
176
February1st to 10thDay
21%26%41%9%4
160
11th to 20thDay
15%25%36%19%6%
257
21st to endDay
16%28%35%17%31
346
March1st to 10thDay
25%28%29%11%7%
420
11th to 20thDay
25%23%27%19%5%2
420
21st to endDay
24%32%24%14%5%2
462
April1st to 10thDay
24%23%29%19%41
420
11th to 20thDay
25%26%28%12%7%2
412
21st to endDay
27%21%32%12%7%1
420
May1st to 10thDay
24%17%30%17%8%3
423
11th to 20thDay
25%14%25%21%13%3
561
21st to endDay
26%15%22%22%13%2
679
June1st to 10thDay
24%21%27%17%10%1
630
11th to 20thDay
26%21%25%18%10%1
630
21st to endDay
13%18%26%25%13%4
630
July1st to 10thDay
11%14%28%29%15%3
621
11th to 20thDay
12%17%32%25%12%1
618
21st to endDay
8%17%37%23%12%3
498
August1st to 10thDay
11%16%35%25%10%3
447
11th to 20thDay
7%18%34%26%11%4
437
21st to endDay
13%22%34%19%9%3
495
September1st to 10thDay
20%25%29%16%7%2
450
11th to 20thDay
16%21%33%19%7%3
450
21st to endDay
26%26%26%16%5%1
450
October1st to 10thDay
24%19%27%20%8%2
414
11th to 20thDay
26%18%27%16%11%2
270
21st to endDay
29%19%28%19%41
297
November1st to 10thDay
29%21%28%19%3
270
11th to 20thDay
22%23%35%16%31
243
21st to endDay
19%24%29%13%9%6%
180
December1st to 10thDay
26%23%26%15%8%2
180
11th to 20thDay
17%27%38%16%21
180
21st to endDay
14%20%37%22%6%1
198
January1st to 10thNight
17%20%41%18%41
950
11th to 20thNight
13%19%45%19%4
801
21st to endNight
10%16%46%21%5%1
792
February1st to 10thNight
15%14%43%20%7%
720
11th to 20thNight
12%15%41%26%5%
704
21st to endNight
11%14%35%29%9%1
592
March1st to 10thNight
14%18%37%23%7%1
720
11th to 20thNight
18%17%26%28%10%1
720
21st to endNight
16%14%30%29%8%2
792
April1st to 10thNight
14%16%25%34%11%1
716
11th to 20thNight
16%19%28%27%11%
533
21st to endNight
15%17%27%30%11%1
540
May1st to 10thNight
19%12%21%33%14%2
461
11th to 20thNight
14%9%20%32%22%3
354
21st to endNight
24%9%18%27%21%2
389
June1st to 10thNight
18%11%22%31%16%2
360
11th to 20thNight
22%11%26%27%14%
360
21st to endNight
10%8%20%37%24%2
360
July1st to 10thNight
5%7%19%43%25%1
350
11th to 20thNight
7%8%23%43%18%1
348
21st to endNight
49%19%41%26%1
394
August1st to 10thNight
6%6%16%42%28%1
358
11th to 20thNight
7%8%18%39%26%2
508
21st to endNight
10%13%22%35%19%1
594
September1st to 10thNight
10%10%22%33%20%4
695
11th to 20thNight
14%9%22%31%19%5%
720
21st to endNight
17%12%25%30%13%3
720
October1st to 10thNight
18%11%22%35%13%2
720
11th to 20thNight
15%13%28%31%12%1
720
21st to endNight
17%17%31%28%7%
792
November1st to 10thNight
25%13%36%21%5%
749
11th to 20thNight
20%20%37%19%3
950
21st to endNight
16%17%38%21%7%1
950
December1st to 10thNight
17%16%40%21%6%1
950
11th to 20thNight
12%19%45%19%3
950
21st to endNight
13%17%44%21%4
1045
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