Streator
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Streator clear sky chart from 2005-11-05 to 2018-03-11.

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%
16714
18%
49095
11%
16671
44%
16671
24%
32736

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
20%
975
15%
2716
4%
970
29%
970
19%
1944
January16th to endNight
21%
1040
13%
2827
4%
1040
28%
1040
17%
2129
February1st to 15thNight
24%
879
13%
2410
5%
879
30%
879
19%
1741
February16th to endNight
25%
683
17%
2049
8%
683
34%
683
18%
1442
March1st to 15thNight
28%
764
15%
2292
8%
764
33%
764
19%
1587
March16th to endNight
28%
591
14%
2001
8%
591
36%
591
17%
1396
April1st to 15thNight
28%
539
16%
1797
10%
539
38%
539
21%
1208
April16th to endNight
34%
540
18%
1771
12%
540
44%
540
22%
1172
May1st to 15thNight
34%
540
16%
1584
9%
540
41%
540
23%
1100
May16th to endNight
50%
563
19%
1498
10%
561
56%
561
31%
976
June1st to 15thNight
53%
540
17%
1440
11%
540
57%
540
36%
910
June16th to endNight
52%
540
17%
1440
10%
540
56%
540
34%
932
July1st to 15thNight
61%
510
17%
1360
11%
510
64%
510
36%
844
July16th to endNight
74%
564
24%
1417
19%
531
76%
531
42%
829
August1st to 15thNight
73%
539
21%
1613
21%
536
75%
536
40%
895
August16th to endNight
68%
573
22%
1910
23%
573
72%
573
33%
1096
September1st to 15thNight
62%
540
29%
1800
29%
540
68%
540
37%
962
September16th to endNight
60%
702
27%
1965
20%
702
65%
702
36%
1173
October1st to 15thNight
47%
720
27%
2097
19%
720
54%
720
33%
1255
October16th to endNight
29%
768
21%
2411
12%
768
39%
768
23%
1535
November1st to 15thNight
32%
760
23%
2471
15%
760
43%
760
24%
1538
November16th to endNight
29%
829
19%
2584
10%
829
38%
829
22%
1701
December1st to 15thNight
22%
975
12%
2730
4%
975
29%
975
18%
2017
December16th to endNight
15%
1040
11%
2912
3%
1040
23%
1040
12%
2354

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
14%8%35%5%3445%7%37%
49532
Night
14%7%35%5%24446%40%
49263
Cloud CoverDay
13%8%35%5%3445%7%37%
49540
Night
14%7%35%5%24446%40%
49268
TransparencyDay
45%6%12%21%12%1
49218
Night
44%5%11%22%14%2
49095
SeeingDay
16%7%25%26%17%6%
6497
Night
17%8%30%29%12%1
16717

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
14%14%5%9%6%34445%25%
1552
16th to endDay
13%15%6%8%7%34446%25%
1745
February1st to 15thDay
15%13%5%8%5%34335%28%
1780
16th to endDay
15%10%5%7%6%3435%6%30%
1710
March1st to 15thDay
16%11%47%42445%6%31%
1895
16th to endDay
17%10%46%5%35%46%7%29%
2232
April1st to 15thDay
17%10%46%5%23335%36%
2151
16th to endDay
20%8%25%5%34446%33%
2187
May1st to 15thDay
19%8%36%5%3435%7%31%
2364
16th to endDay
15%6%344345%5%7%37%
2617
June1st to 15thDay
10%5%25%5%25%46%9%42%
2520
16th to endDay
8%5%26%7%36%5%5%9%39%
2520
July1st to 15thDay
8%5%24425%5%6%9%45%
2520
16th to endDay
6%4145%35%6%7%9%43%
2655
August1st to 15thDay
6%424435%5%7%9%46%
2334
16th to endDay
9%5%2442446%9%45%
2292
September1st to 15thDay
13%313434447%49%
2160
16th to endDay
7%6%25%43346%8%47%
1982
October1st to 15thDay
15%7%24433337%43%
1860
16th to endDay
17%6%36%424435%40%
1812
November1st to 15thDay
16%7%25%42345%6%42%
1717
16th to endDay
18%9%45%423235%39%
1703
December1st to 15thDay
17%11%46%7%45%34430%
1560
16th to endDay
21%14%6%7%6%24346%24%
1664
January1st to 15thNight
15%10%47%5%33345%35%
2716
16th to endNight
12%12%6%8%5%34445%30%
2827
February1st to 15thNight
15%11%47%6%33336%34%
2408
16th to endNight
17%10%47%424446%33%
2049
March1st to 15thNight
17%9%36%5%24345%37%
2279
16th to endNight
16%8%36%6%345%5%7%31%
2001
April1st to 15thNight
16%8%45%5%23446%37%
1797
16th to endNight
18%7%26%423347%38%
1771
May1st to 15thNight
19%6%36%5%1345%8%34%
1584
16th to endNight
10%4245%245%6%8%43%
1496
June1st to 15thNight
11%5%2442345%7%48%
1440
16th to endNight
7%5%25%6%346%5%10%43%
1440
July1st to 15thNight
6%4245%25%45%9%49%
1440
16th to endNight
4323425%47%9%52%
1513
August1st to 15thNight
34135%35%46%9%52%
1622
16th to endNight
8%31442436%8%51%
1910
September1st to 15thNight
11%313413346%56%
1800
16th to endNight
7%315%435%45%8%50%
1965
October1st to 15thNight
12%424413346%51%
2097
16th to endNight
17%7%34423335%43%
2411
November1st to 15thNight
13%7%245%33445%45%
2471
16th to endNight
16%8%35%424346%40%
2584
December1st to 15thNight
18%10%48%424335%32%
2730
16th to endNight
22%14%5%9%6%3433422%
2912

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
14%14%5%9%6%35%445%25%
1552
16th to endDay
13%16%6%8%7%25%346%25%
1745
February1st to 15thDay
16%12%6%8%5%35%335%28%
1780
16th to endDay
15%10%5%8%5%3335%6%30%
1710
March1st to 15thDay
16%11%5%7%5%3445%6%31%
1905
16th to endDay
16%10%46%6%35%46%8%29%
2230
April1st to 15thDay
17%10%46%433245%36%
2151
16th to endDay
20%7%25%5%35%446%33%
2187
May1st to 15thDay
19%9%26%5%3445%8%30%
2364
16th to endDay
15%6%35%4345%5%7%37%
2617
June1st to 15thDay
10%425%5%25%5%6%8%43%
2520
16th to endDay
8%5%26%6%36%5%6%9%39%
2520
July1st to 15thDay
8%4244345%6%9%45%
2520
16th to endDay
6%4245%35%6%7%10%43%
2655
August1st to 15thDay
6%424435%5%6%9%46%
2334
16th to endDay
9%5%245%2446%8%45%
2292
September1st to 15thDay
12%314424447%49%
2160
16th to endDay
7%6%25%33445%8%48%
1982
October1st to 15thDay
15%7%25%423347%43%
1860
16th to endDay
17%7%35%5%24435%40%
1812
November1st to 15thDay
16%7%2442445%6%41%
1717
16th to endDay
18%9%45%42224439%
1703
December1st to 15thDay
17%10%5%7%7%34445%30%
1560
16th to endDay
20%14%6%7%5%24346%24%
1664
January1st to 15thNight
15%10%47%5%33345%35%
2716
16th to endNight
12%12%6%8%6%34445%30%
2827
February1st to 15thNight
15%11%46%6%34245%34%
2401
16th to endNight
17%9%47%434446%34%
2049
March1st to 15thNight
17%9%36%5%24335%37%
2292
16th to endNight
16%8%36%6%35%5%5%7%31%
2001
April1st to 15thNight
16%8%45%5%24446%38%
1797
16th to endNight
17%7%25%5%2335%6%38%
1771
May1st to 15thNight
19%5%35%5%2346%8%34%
1583
16th to endNight
10%425%5%245%6%9%43%
1496
June1st to 15thNight
11%5%2432345%7%49%
1440
16th to endNight
7%4245%35%5%5%10%43%
1440
July1st to 15thNight
6%3245%25%5%5%9%50%
1440
16th to endNight
3323425%6%6%10%52%
1513
August1st to 15thNight
43135%3446%9%52%
1622
16th to endNight
8%42442445%8%50%
1910
September1st to 15thNight
11%313323337%56%
1800
16th to endNight
7%415%434448%50%
1965
October1st to 15thNight
12%424413336%51%
2097
16th to endNight
17%8%24423336%43%
2411
November1st to 15thNight
12%8%25%424445%45%
2471
16th to endNight
16%7%35%423346%40%
2584
December1st to 15thNight
19%10%49%423335%32%
2730
16th to endNight
21%14%6%8%6%3433423%
2912

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
60%311%13%9%1
1553
16th to endDay
60%311%16%6%
1745
February1st to 15thDay
57%5%12%16%5%1
1782
16th to endDay
53%413%20%6%1
1710
March1st to 15thDay
53%5%13%20%6%
1905
16th to endDay
53%6%14%19%5%1
2232
April1st to 15thDay
50%411%22%11%
2151
16th to endDay
50%5%12%17%10%3
2187
May1st to 15thDay
51%6%12%22%6%
2364
16th to endDay
44%6%12%19%15%1
2621
June1st to 15thDay
36%7%12%25%16%1
2520
16th to endDay
39%8%11%21%16%2
2520
July1st to 15thDay
34%8%12%25%15%3
2371
16th to endDay
32%9%18%24%13%2
2488
August1st to 15thDay
31%8%15%26%17%1
2319
16th to endDay
34%7%13%25%16%3
2292
September1st to 15thDay
34%411%25%19%5%
2160
16th to endDay
33%5%11%26%21%1
1982
October1st to 15thDay
41%411%24%15%2
1860
16th to endDay
46%412%23%12%1
1812
November1st to 15thDay
42%411%24%14%2
1717
16th to endDay
49%312%25%8%
1703
December1st to 15thDay
58%411%19%7%
1560
16th to endDay
62%5%10%13%7%
1664
January1st to 15thNight
50%5%11%18%13%
2716
16th to endNight
54%5%13%17%8%
2827
February1st to 15thNight
52%411%19%10%1
2410
16th to endNight
51%412%21%9%1
2049
March1st to 15thNight
49%412%21%10%1
2292
16th to endNight
50%6%13%19%9%1
2001
April1st to 15thNight
47%410%21%13%2
1797
16th to endNight
46%410%21%11%5%
1771
May1st to 15thNight
46%5%11%22%12%
1584
16th to endNight
35%8%14%21%17%2
1498
June1st to 15thNight
34%5%12%25%18%3
1440
16th to endNight
35%7%13%22%17%4
1440
July1st to 15thNight
31%7%12%26%17%3
1360
16th to endNight
26%7%14%27%19%4
1417
August1st to 15thNight
26%6%15%29%19%2
1613
16th to endNight
30%7%10%26%19%4
1910
September1st to 15thNight
29%39%26%25%5%
1800
16th to endNight
31%5%11%27%21%2
1965
October1st to 15thNight
34%49%26%22%3
2097
16th to endNight
43%39%25%16%1
2411
November1st to 15thNight
40%5%8%23%16%4
2471
16th to endNight
45%412%25%12%
2584
December1st to 15thNight
54%5%10%19%9%
2730
16th to endNight
66%38%14%6%
2912

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
28%13%25%22%9%
135
16th to endDay
18%13%40%17%9%
144
February1st to 15thDay
25%12%40%19%2
135
16th to endDay
25%15%37%14%8%
120
March1st to 15thDay
28%16%27%23%4
121
16th to endDay
28%12%30%17%9%1
222
April1st to 15thDay
22%11%31%22%10%
270
16th to endDay
22%9%25%24%12%4
270
May1st to 15thDay
21%13%29%19%11%3
321
16th to endDay
19%7%28%25%13%5%
517
June1st to 15thDay
11%227%33%20%5%
495
16th to endDay
11%7%30%27%17%4
495
July1st to 15thDay
10%323%28%22%11%
475
16th to endDay
6%121%31%26%11%
515
August1st to 15thDay
9%114%31%26%15%
413
16th to endDay
7%215%30%29%14%
332
September1st to 15thDay
10%313%30%31%9%
315
16th to endDay
9%415%29%30%9%
314
October1st to 15thDay
21%8%21%26%20%3
195
16th to endDay
27%7%30%27%6%
144
November1st to 15thDay
17%5%32%20%14%8%
135
16th to endDay
31%9%31%17%9%
135
December1st to 15thDay
15%24%30%22%7%
135
16th to endDay
27%15%46%9%2
144
January1st to 15thNight
20%11%40%20%6%
975
16th to endNight
19%13%36%27%3
1040
February1st to 15thNight
22%10%36%26%3
882
16th to endNight
22%11%35%25%4
683
March1st to 15thNight
22%10%34%25%6%
764
16th to endNight
20%8%37%24%8%1
591
April1st to 15thNight
20%12%34%26%5%
539
16th to endNight
21%8%32%28%9%
540
May1st to 15thNight
22%5%32%29%9%
540
16th to endNight
11%428%39%14%1
563
June1st to 15thNight
13%224%45%12%
540
16th to endNight
11%227%42%17%
540
July1st to 15thNight
10%21%37%28%2
510
16th to endNight
4112%46%31%3
564
August1st to 15thNight
5%12%42%33%5%
539
16th to endNight
9%14%38%34%2
573
September1st to 15thNight
13%315%34%29%4
540
16th to endNight
8%419%35%28%2
702
October1st to 15thNight
15%5%25%32%18%1
720
16th to endNight
21%11%33%24%9%
768
November1st to 15thNight
16%10%37%24%10%
760
16th to endNight
19%12%35%24%7%
829
December1st to 15thNight
23%11%35%23%5%
975
16th to endNight
29%10%34%21%3
1040
Page generated at 2018-03-12 12:28:12. Version ac04

Copyright 2018 A. Danko


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