Auburn / Lewiston
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Auburn / Lewiston clear sky chart from 2005-11-05 to 2018-01-12.

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
28%
15279
17%
48527
8%
15247
39%
15247
19%
32279

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
21%
765
18%
2662
7%
761
34%
761
16%
1704
January16th to endNight
16%
768
17%
2688
4%
768
33%
768
14%
1765
February1st to 15thNight
17%
704
14%
2253
5%
701
29%
701
14%
1578
February16th to endNight
19%
631
19%
1893
6%
631
35%
631
18%
1288
March1st to 15thNight
17%
720
15%
2130
5%
720
29%
720
17%
1509
March16th to endNight
25%
768
21%
2070
6%
768
36%
768
22%
1374
April1st to 15thNight
22%
718
17%
1796
3%
718
30%
718
21%
1304
April16th to endNight
25%
540
16%
1620
6%
540
33%
540
18%
1126
May1st to 15thNight
29%
540
13%
1620
6%
540
36%
540
16%
1139
May16th to endNight
28%
411
11%
1533
8%
410
35%
410
14%
1099
June1st to 15thNight
33%
360
8%
1440
7%
360
40%
360
13%
1033
June16th to endNight
44%
360
9%
1440
11%
360
50%
360
20%
928
July1st to 15thNight
48%
340
10%
1360
14%
340
51%
340
20%
859
July16th to endNight
50%
376
12%
1418
13%
354
56%
354
20%
881
August1st to 15thNight
46%
509
13%
1580
9%
507
50%
507
23%
1034
August16th to endNight
47%
642
21%
1788
11%
642
51%
642
32%
1116
September1st to 15thNight
41%
720
18%
1884
9%
720
47%
720
33%
1212
September16th to endNight
45%
717
26%
1980
15%
717
54%
717
36%
1162
October1st to 15thNight
37%
720
21%
2031
10%
720
46%
720
26%
1320
October16th to endNight
21%
768
16%
2490
7%
768
34%
768
19%
1642
November1st to 15thNight
31%
760
20%
2472
12%
760
43%
760
21%
1588
November16th to endNight
26%
780
21%
2535
8%
780
40%
780
19%
1637
December1st to 15thNight
19%
824
15%
2906
3%
824
33%
824
15%
1976
December16th to endNight
18%
838
18%
2938
5%
838
34%
838
14%
2005

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
18%6%25%42445%6%38%
48802
Night
18%7%25%424446%38%
48697
Cloud CoverDay
18%6%25%42445%6%38%
48812
Night
18%7%24424446%39%
48702
TransparencyDay
45%5%11%21%13%1
48490
Night
45%5%11%22%13%1
48527
SeeingDay
22%14%30%20%9%3
6205
Night
22%11%31%25%8%
15279

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
17%6%344245%5%7%38%
1520
16th to endDay
15%9%35%3245%46%40%
1536
February1st to 15thDay
16%8%26%5%35%445%34%
1603
16th to endDay
14%9%36%5%35%5%5%5%35%
1580
March1st to 15thDay
19%9%25%5%2435%6%34%
1820
16th to endDay
15%7%35%5%24445%41%
2151
April1st to 15thDay
19%7%34435%445%37%
2152
16th to endDay
20%5%15%5%24445%39%
2340
May1st to 15thDay
26%7%26%5%23346%30%
2332
16th to endDay
20%6%25%43445%7%34%
2590
June1st to 15thDay
25%7%35%423447%29%
2520
16th to endDay
20%6%245%35%5%5%7%32%
2520
July1st to 15thDay
13%5%25%5%36%6%7%8%34%
2520
16th to endDay
13%5%25%6%36%5%7%9%34%
2654
August1st to 15thDay
15%5%25%5%35%45%8%37%
2358
16th to endDay
12%32442346%8%46%
2411
September1st to 15thDay
15%5%145%23345%47%
2075
16th to endDay
14%422322347%52%
1980
October1st to 15thDay
18%7%25%5%23345%41%
1929
16th to endDay
19%6%25%424346%40%
1731
November1st to 15thDay
20%6%2431445%6%40%
1716
16th to endDay
22%5%2431335%5%43%
1755
December1st to 15thDay
21%9%35%43334436%
1377
16th to endDay
22%10%36%423335%33%
1632
January1st to 15thNight
15%8%3442435%7%40%
2662
16th to endNight
15%9%26%425%45%5%37%
2688
February1st to 15thNight
14%8%36%7%46%5%46%33%
2252
16th to endNight
16%9%34435%445%38%
1893
March1st to 15thNight
19%10%26%434445%34%
2117
16th to endNight
16%6%25%324345%44%
2070
April1st to 15thNight
19%7%35%435%445%35%
1796
16th to endNight
22%5%25%5%34445%37%
1620
May1st to 15thNight
20%7%345%35%45%7%33%
1620
16th to endNight
22%8%35%5%3445%7%28%
1531
June1st to 15thNight
24%7%26%434446%30%
1440
16th to endNight
19%6%2442446%8%35%
1440
July1st to 15thNight
14%5%25%5%45%45%8%37%
1440
16th to endNight
14%5%145%26%5%6%8%39%
1514
August1st to 15thNight
14%425%5%35%5%5%9%38%
1590
16th to endNight
13%5%1432245%9%46%
1788
September1st to 15thNight
15%5%23423337%49%
1884
16th to endNight
13%423322447%52%
1980
October1st to 15thNight
17%6%2333345%6%43%
2031
16th to endNight
22%5%24423446%37%
2490
November1st to 15thNight
18%6%24324446%43%
2472
16th to endNight
17%6%24434345%42%
2535
December1st to 15thNight
23%8%25%423345%35%
2906
16th to endNight
22%9%24424435%36%
2938

Percentage Cloud Cover SE (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
17%6%344345%47%39%
1520
16th to endDay
16%8%34225%45%6%40%
1536
February1st to 15thDay
16%8%35%6%346%45%34%
1603
16th to endDay
14%9%35%5%25%5%46%35%
1580
March1st to 15thDay
20%9%35%5%24346%34%
1830
16th to endDay
15%7%26%5%33346%41%
2151
April1st to 15thDay
19%6%35%4245%46%37%
2152
16th to endDay
21%425%5%2445%6%38%
2340
May1st to 15thDay
26%7%25%5%23445%31%
2332
16th to endDay
21%5%35%43445%7%33%
2590
June1st to 15thDay
26%6%25%42445%7%30%
2520
16th to endDay
20%6%25%5%45%5%47%32%
2520
July1st to 15thDay
13%5%25%5%46%5%6%8%36%
2520
16th to endDay
14%4246%36%5%7%8%34%
2654
August1st to 15thDay
15%5%25%5%345%6%9%36%
2358
16th to endDay
12%4144335%6%8%46%
2411
September1st to 15thDay
14%6%14423346%47%
2075
16th to endDay
13%314322346%52%
1980
October1st to 15thDay
19%6%25%423335%42%
1929
16th to endDay
19%6%25%324346%41%
1731
November1st to 15thDay
20%6%14323446%41%
1716
16th to endDay
22%5%23412345%43%
1755
December1st to 15thDay
21%9%24423345%36%
1377
16th to endDay
23%10%36%324335%33%
1632
January1st to 15thNight
15%8%34424446%40%
2662
16th to endNight
16%9%35%434445%37%
2688
February1st to 15thNight
14%8%35%7%46%446%33%
2245
16th to endNight
16%10%34425%345%39%
1893
March1st to 15thNight
19%10%25%5%33445%34%
2130
16th to endNight
17%6%34424345%43%
2069
April1st to 15thNight
20%8%24434445%36%
1796
16th to endNight
22%5%25%5%35%345%36%
1620
May1st to 15thNight
20%7%345%345%5%7%33%
1620
16th to endNight
22%7%46%5%3346%6%28%
1531
June1st to 15thNight
25%6%36%434445%31%
1440
16th to endNight
19%6%3432445%8%36%
1440
July1st to 15thNight
13%5%26%5%36%45%7%37%
1440
16th to endNight
14%5%24426%5%6%8%38%
1514
August1st to 15thNight
14%325%5%35%5%6%8%39%
1590
16th to endNight
14%32332446%9%46%
1788
September1st to 15thNight
14%5%14313347%48%
1884
16th to endNight
13%422322347%53%
1980
October1st to 15thNight
18%6%23423446%43%
2031
16th to endNight
22%5%25%423446%38%
2490
November1st to 15thNight
18%6%23424446%43%
2472
16th to endNight
17%6%24423446%42%
2535
December1st to 15thNight
22%8%34423446%35%
2906
16th to endNight
22%9%25%324335%37%
2938

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
44%5%12%21%13%1
1521
16th to endDay
43%5%12%24%12%1
1536
February1st to 15thDay
50%5%12%19%11%
1606
16th to endDay
48%411%19%13%2
1580
March1st to 15thDay
50%411%17%12%2
1830
16th to endDay
43%5%8%18%19%4
2151
April1st to 15thDay
47%5%8%19%16%3
2152
16th to endDay
45%6%10%19%14%4
2340
May1st to 15thDay
53%5%8%16%14%2
2332
16th to endDay
48%6%12%18%11%1
2594
June1st to 15thDay
53%6%11%18%9%
2520
16th to endDay
50%7%9%19%11%1
2520
July1st to 15thDay
41%8%14%23%11%
2371
16th to endDay
42%8%15%21%10%
2487
August1st to 15thDay
42%8%15%24%9%
2344
16th to endDay
33%6%15%25%17%1
2411
September1st to 15thDay
37%5%10%26%18%1
2075
16th to endDay
32%410%29%21%1
1980
October1st to 15thDay
44%49%24%14%1
1929
16th to endDay
44%312%25%12%
1731
November1st to 15thDay
43%5%14%22%13%1
1716
16th to endDay
42%5%14%19%15%1
1755
December1st to 15thDay
50%411%20%12%
1377
16th to endDay
53%410%15%13%1
1632
January1st to 15thNight
43%6%12%23%12%1
2662
16th to endNight
47%410%20%14%2
2688
February1st to 15thNight
50%5%12%19%11%1
2253
16th to endNight
47%411%20%13%2
1893
March1st to 15thNight
51%410%19%12%2
2130
16th to endNight
41%5%10%19%18%5%
2070
April1st to 15thNight
49%47%18%16%2
1796
16th to endNight
48%6%9%19%12%3
1620
May1st to 15thNight
49%7%10%17%13%2
1620
16th to endNight
53%6%12%15%10%1
1533
June1st to 15thNight
54%6%10%17%8%1
1440
16th to endNight
44%6%14%20%12%
1440
July1st to 15thNight
42%7%15%22%11%
1360
16th to endNight
41%7%17%22%10%
1418
August1st to 15thNight
41%8%15%25%9%
1580
16th to endNight
34%7%13%28%16%
1788
September1st to 15thNight
36%5%11%30%15%1
1884
16th to endNight
31%411%32%17%1
1980
October1st to 15thNight
40%5%11%25%15%1
2031
16th to endNight
46%412%24%11%1
2490
November1st to 15thNight
42%5%12%23%14%1
2472
16th to endNight
43%5%12%21%15%1
2535
December1st to 15thNight
50%411%21%11%
2906
16th to endNight
50%5%10%19%13%1
2938

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
17%21%34%20%6%
82
16th to endDay
23%28%26%18%3
64
February1st to 15thDay
27%16%35%16%4
217
16th to endDay
19%19%35%21%4
239
March1st to 15thDay
27%22%29%16%3
270
16th to endDay
20%25%29%13%6%3
288
April1st to 15thDay
28%15%30%17%6%2
270
16th to endDay
24%16%32%15%7%3
270
May1st to 15thDay
37%13%23%16%7%1
288
16th to endDay
25%13%33%21%5%
331
June1st to 15thDay
24%16%30%19%8%
315
16th to endDay
23%10%34%20%7%2
315
July1st to 15thDay
15%5%37%25%11%3
305
16th to endDay
13%6%36%26%13%3
326
August1st to 15thDay
16%9%24%30%15%3
313
16th to endDay
13%9%21%29%16%9%
332
September1st to 15thDay
19%7%28%22%16%5%
315
16th to endDay
15%9%28%19%14%13%
314
October1st to 15thDay
20%13%25%20%15%4
302
16th to endDay
25%16%28%20%8%
288
November1st to 15thDay
25%12%30%20%8%2
280
16th to endDay
27%16%25%21%7%1
285
December1st to 15thDay
23%18%37%14%8%
100
16th to endDay
32%27%30%10%
96
January1st to 15thNight
20%18%34%22%3
765
16th to endNight
22%18%36%19%2
768
February1st to 15thNight
20%17%36%22%3
704
16th to endNight
23%15%35%21%5%
631
March1st to 15thNight
25%16%36%17%3
720
16th to endNight
20%16%33%21%5%
768
April1st to 15thNight
24%15%34%20%4
718
16th to endNight
25%15%30%22%5%
540
May1st to 15thNight
24%11%30%26%6%
540
16th to endNight
26%7%30%29%5%
411
June1st to 15thNight
28%5%27%28%9%
360
16th to endNight
22%226%37%11%
360
July1st to 15thNight
16%126%36%19%
340
16th to endNight
15%223%38%19%
376
August1st to 15thNight
14%325%39%16%
509
16th to endNight
14%328%32%19%2
642
September1st to 15thNight
17%430%29%15%2
720
16th to endNight
16%6%27%27%20%2
717
October1st to 15thNight
21%9%27%27%13%1
720
16th to endNight
26%13%34%19%6%
768
November1st to 15thNight
22%10%32%25%8%1
760
16th to endNight
21%15%31%23%6%1
780
December1st to 15thNight
28%12%34%20%4
824
16th to endNight
28%17%31%20%2
838
Page generated at 2018-01-12 22:01:30. Version ac04

Copyright 2018 A. Danko


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