Lewiston Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lewiston Lake clear sky chart from 2005-11-05 to 2017-09-19.

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
59%
15067
25%
46909
21%
15028
64%
15028
36%
26268

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
51%
719
18%
2458
15%
716
57%
716
22%
1564
January16th to endNight
49%
768
24%
2496
23%
768
53%
768
25%
1572
February1st to 15thNight
49%
697
19%
2288
19%
697
53%
697
22%
1533
February16th to endNight
45%
632
19%
1960
15%
632
51%
632
24%
1277
March1st to 15thNight
43%
720
14%
2004
10%
720
46%
720
21%
1423
March16th to endNight
42%
768
18%
2099
11%
768
47%
768
26%
1401
April1st to 15thNight
38%
719
17%
1799
6%
719
44%
719
26%
1241
April16th to endNight
53%
687
23%
1767
11%
687
57%
687
44%
1015
May1st to 15thNight
55%
497
24%
1577
16%
497
62%
497
46%
765
May16th to endNight
58%
374
22%
1496
21%
374
65%
374
33%
733
June1st to 15thNight
61%
360
21%
1440
24%
360
69%
360
36%
695
June16th to endNight
71%
360
32%
1440
40%
360
79%
360
60%
511
July1st to 15thNight
88%
340
31%
1360
42%
340
91%
340
69%
440
July16th to endNight
91%
514
38%
1543
39%
481
93%
481
77%
576
August1st to 15thNight
91%
538
38%
1611
33%
535
92%
535
76%
636
August16th to endNight
88%
711
44%
1857
31%
711
89%
711
81%
800
September1st to 15thNight
85%
720
44%
1800
28%
720
89%
720
87%
774
September16th to endNight
76%
671
38%
1850
32%
671
81%
671
62%
872
October1st to 15thNight
66%
660
29%
1980
26%
660
74%
660
49%
983
October16th to endNight
65%
704
30%
2112
28%
704
70%
704
40%
1154
November1st to 15thNight
59%
700
21%
2244
19%
700
64%
700
29%
1346
November16th to endNight
51%
720
17%
2520
17%
720
55%
720
24%
1542
December1st to 15thNight
48%
720
18%
2520
16%
720
53%
720
22%
1614
December16th to endNight
40%
768
19%
2688
15%
768
47%
768
19%
1801

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%312323346%58%
47910
Night
12%312213346%56%
47093
TransparencyDay
27%49%20%22%15%
47593
Night
30%410%21%21%11%
46910
SeeingDay
13%13%26%28%14%3
5880
Night
14%417%33%26%4
15077

By Month

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
18%5%13225%5%5%7%42%
1477
16th to endDay
21%6%23323336%44%
1728
February1st to 15thDay
22%5%1332445%6%38%
1576
16th to endDay
17%7%245%24447%39%
1513
March1st to 15thDay
24%7%35%32445%8%31%
1956
16th to endDay
21%6%13423447%38%
2124
April1st to 15thDay
20%5%2342446%8%36%
2149
16th to endDay
7%4235%23446%55%
2190
May1st to 15thDay
6%313223447%60%
2373
16th to endDay
10%423423447%53%
2615
June1st to 15thDay
6%31332335%5%60%
2520
16th to endDay
41111222476%
2520
July1st to 15thDay
111213480%
2520
16th to endDay
111123284%
2516
August1st to 15thDay
111123483%
2340
16th to endDay
111112384%
2344
September1st to 15thDay
111123482%
2160
16th to endDay
311212335%73%
1851
October1st to 15thDay
9%212213235%64%
1650
16th to endDay
13%423322347%52%
1760
November1st to 15thDay
12%42342445%8%46%
1612
16th to endDay
16%5%14435%436%43%
1440
December1st to 15thDay
21%6%1432445%6%39%
1440
16th to endDay
27%5%1342236%7%35%
1536
January1st to 15thNight
17%6%24314447%42%
2458
16th to endNight
21%6%13313436%45%
2496
February1st to 15thNight
22%6%2432445%6%37%
2276
16th to endNight
17%5%25%41345%8%40%
1960
March1st to 15thNight
24%6%24324349%34%
2004
16th to endNight
20%42332335%7%42%
2099
April1st to 15thNight
15%5%34423447%42%
1799
16th to endNight
8%42213337%60%
1767
May1st to 15thNight
5%312123347%64%
1577
16th to endNight
9%212323347%59%
1496
June1st to 15thNight
6%322213446%60%
1440
16th to endNight
31111121479%
1440
July1st to 15thNight
111223481%
1440
16th to endNight
111111386%
1650
August1st to 15thNight
111113384%
1620
16th to endNight
111121386%
1857
September1st to 15thNight
12488%
1800
16th to endNight
311212236%73%
1850
October1st to 15thNight
8%22312335%67%
1980
16th to endNight
11%313222337%58%
2112
November1st to 15thNight
12%4233245%5%8%47%
2244
16th to endNight
16%41432446%8%43%
2520
December1st to 15thNight
25%5%13313346%41%
2520
16th to endNight
26%5%1332345%5%37%
2688

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
41%7%10%20%13%6%
1477
16th to endDay
43%48%15%16%10%
1728
February1st to 15thDay
45%6%10%18%16%2
1576
16th to endDay
45%5%12%23%11%1
1513
March1st to 15thDay
51%7%10%13%14%2
1956
16th to endDay
45%6%15%18%10%3
2124
April1st to 15thDay
44%7%13%20%13%
2149
16th to endDay
29%5%12%27%18%5%
2190
May1st to 15thDay
22%5%12%26%23%8%
2373
16th to endDay
31%411%27%20%4
2619
June1st to 15thDay
25%5%8%23%24%13%
2520
16th to endDay
14%25%19%37%20%
2520
July1st to 15thDay
8%25%16%34%33%
2371
16th to endDay
7%2310%30%44%
2360
August1st to 15thDay
7%15%20%32%32%
2324
16th to endDay
7%1316%34%36%
2344
September1st to 15thDay
7%2413%32%39%
2160
16th to endDay
13%37%21%33%19%
1851
October1st to 15thDay
23%48%22%25%14%
1650
16th to endDay
31%410%25%16%11%
1760
November1st to 15thDay
35%6%14%24%12%7%
1612
16th to endDay
41%5%12%17%16%7%
1440
December1st to 15thDay
45%5%8%19%16%4
1440
16th to endDay
47%5%10%16%14%4
1536
January1st to 15thNight
41%6%11%18%14%6%
2458
16th to endNight
41%48%18%15%10%
2496
February1st to 15thNight
46%5%10%17%16%4
2288
16th to endNight
41%7%12%23%13%2
1960
March1st to 15thNight
48%6%10%16%15%2
2004
16th to endNight
40%6%15%22%11%3
2099
April1st to 15thNight
41%6%15%19%14%2
1799
16th to endNight
24%5%16%31%18%3
1767
May1st to 15thNight
19%5%14%30%23%5%
1578
16th to endNight
25%6%14%34%15%3
1496
June1st to 15thNight
23%6%15%23%23%7%
1440
16th to endNight
12%15%28%39%12%
1440
July1st to 15thNight
6%2422%36%26%
1360
16th to endNight
7%1315%32%40%
1543
August1st to 15thNight
7%15%24%36%23%
1611
16th to endNight
6%1421%39%26%
1857
September1st to 15thNight
31418%35%36%
1800
16th to endNight
13%27%24%29%22%
1850
October1st to 15thNight
21%38%24%29%13%
1980
16th to endNight
27%410%26%20%10%
2112
November1st to 15thNight
34%7%16%23%12%5%
2244
16th to endNight
38%6%11%19%16%6%
2520
December1st to 15thNight
45%49%16%20%3
2520
16th to endNight
47%5%8%15%16%4
2688

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
34%11%25%16%10%1
105
16th to endDay
26%12%21%18%16%4
256
February1st to 15thDay
27%10%26%23%11%
236
16th to endDay
22%18%27%22%9%
227
March1st to 15thDay
32%17%25%17%6%1
270
16th to endDay
27%21%28%15%6%
288
April1st to 15thDay
28%20%24%18%6%1
269
16th to endDay
15%29%28%18%7%1
270
May1st to 15thDay
8%25%29%27%8%1
288
16th to endDay
12%16%24%26%14%5%
330
June1st to 15thDay
6%23%27%28%12%1
315
16th to endDay
412%33%33%14%1
315
July1st to 15thDay
3425%41%19%5%
305
16th to endDay
16%21%47%18%5%
327
August1st to 15thDay
6%27%42%17%6%
315
16th to endDay
25%28%32%23%7%
332
September1st to 15thDay
25%26%37%22%5%
315
16th to endDay
411%26%35%17%3
268
October1st to 15thDay
14%12%28%24%15%3
255
16th to endDay
18%8%27%27%15%1
272
November1st to 15thDay
11%9%23%32%19%2
138
16th to endDay
20%16%33%23%5%1
60
December1st to 15thDay
36%10%33%18%1
60
16th to endDay
15%435%29%14%
64
January1st to 15thNight
19%318%36%17%5%
720
16th to endNight
23%318%27%22%5%
768
February1st to 15thNight
23%317%32%22%1
704
16th to endNight
21%6%19%34%14%3
632
March1st to 15thNight
26%7%16%27%18%3
720
16th to endNight
20%8%23%32%14%
768
April1st to 15thNight
16%10%28%26%14%2
719
16th to endNight
10%6%27%34%18%3
687
May1st to 15thNight
6%332%38%18%1
498
16th to endNight
8%5%22%33%29%1
375
June1st to 15thNight
6%423%37%26%
360
16th to endNight
3120%45%28%
360
July1st to 15thNight
7%36%51%2
340
16th to endNight
15%38%49%4
514
August1st to 15thNight
1437%49%6%
538
16th to endNight
27%36%47%5%
711
September1st to 15thNight
1110%32%48%5%
720
16th to endNight
4312%34%40%5%
671
October1st to 15thNight
9%317%34%30%5%
660
16th to endNight
13%314%33%28%6%
704
November1st to 15thNight
13%219%37%20%5%
700
16th to endNight
19%5%19%30%21%5%
720
December1st to 15thNight
28%216%30%16%6%
720
16th to endNight
27%423%30%11%2
768
Page generated at 2017-09-20 01:49:55. Version ac04

Copyright 2017 A. Danko


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