Port Burwell Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Burwell Provincial Park clear sky chart from 2005-11-06 to 2024-01-22.

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
35%
23084
9%
74699
6%
23036
39%
23036
9%
61048

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%
758
4%
2535
1%
757
18%
757
3%
2293
January11th to 20thNight
15%
760
2%
2470
1%
760
16%
760
3%
2258
January21st to endNight
17%
800
5%
2599
2%
800
20%
800
5%
2294
February1st to 10thNight
16%
720
4%
2340
2%
720
20%
720
5%
2043
February11th to 20thNight
20%
700
6%
2275
2%
700
25%
700
5%
1960
February21st to endNight
18%
592
7%
1793
2%
592
24%
592
8%
1521
March1st to 10thNight
25%
720
12%
2010
6%
720
32%
720
10%
1642
March11th to 20thNight
27%
720
13%
1980
6%
720
33%
720
12%
1596
March21st to endNight
32%
792
11%
2178
6%
792
35%
792
11%
1790
April1st to 10thNight
27%
720
10%
1900
4%
720
31%
720
14%
1517
April11th to 20thNight
32%
597
14%
1661
6%
597
37%
597
13%
1306
April21st to endNight
37%
540
11%
1620
4%
540
43%
540
11%
1290
May1st to 10thNight
40%
540
10%
1620
7%
540
42%
540
13%
1273
May11th to 20thNight
44%
518
14%
1580
10%
518
49%
518
15%
1193
May21st to endNight
55%
388
13%
1551
15%
388
59%
388
14%
1070
June1st to 10thNight
50%
360
10%
1440
11%
360
56%
360
12%
1043
June11th to 20thNight
51%
360
12%
1401
14%
360
56%
360
13%
987
June21st to endNight
54%
360
15%
1260
13%
360
61%
360
14%
917
July1st to 10thNight
64%
350
12%
1289
16%
350
66%
350
15%
913
July11th to 20thNight
62%
498
12%
1542
12%
498
64%
498
17%
1132
July21st to endNight
62%
591
11%
1672
9%
558
63%
558
17%
1226
August1st to 10thNight
69%
537
11%
1600
9%
534
70%
534
17%
1211
August11th to 20thNight
65%
534
16%
1598
11%
534
67%
534
20%
1146
August21st to endNight
60%
630
15%
1818
10%
630
62%
630
19%
1335
September1st to 10thNight
56%
720
12%
1822
6%
720
59%
720
17%
1418
September11th to 20thNight
63%
720
17%
1980
12%
720
66%
720
18%
1479
September21st to endNight
47%
720
11%
1980
8%
720
50%
720
13%
1603
October1st to 10thNight
45%
720
12%
2137
11%
720
47%
720
13%
1671
October11th to 20thNight
32%
720
8%
2160
5%
720
36%
720
9%
1787
October21st to endNight
27%
792
8%
2376
5%
792
30%
792
8%
1988
November1st to 10thNight
37%
740
12%
2403
10%
740
41%
740
11%
1852
November11th to 20thNight
23%
760
9%
2635
6%
760
29%
760
6%
2230
November21st to endNight
23%
760
6%
2660
6%
760
24%
760
5%
2298
December1st to 10thNight
15%
760
2%
2660
1%
760
17%
760
3%
2428
December11th to 20thNight
13%
760
2%
3275
1%
759
17%
759
2%
2872
December21st to endNight
14%
827
1%
4879
0%
817
16%
817
1%
4466

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
15%8%47%6%35%5%6%8%34%
75008
Night
17%9%47%6%345%5%7%33%
74902
TransparencyDay
32%39%9%13%7%1
74729
Night
35%38%7%12%6%1
74717
SeeingDay
18%10%27%26%14%5%
13688
Night
20%9%28%29%13%2
23099

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 10thDay
18%13%5%11%8%46%5%5%5%20%
1626
11th to 20thDay
18%16%6%13%8%45%5%46%17%
1710
21st to endDay
17%14%7%12%8%46%6%45%18%
1791
February1st to 10thDay
18%15%7%11%6%5%5%5%5%5%19%
1620
11th to 20thDay
16%10%8%12%8%45%5%45%24%
1573
21st to endDay
19%12%5%10%6%35%5%5%6%23%
1462
March1st to 10thDay
16%11%49%7%35%5%6%6%28%
1945
11th to 20thDay
14%11%6%9%6%4445%8%30%
1980
21st to endDay
21%9%48%6%44346%30%
2178
April1st to 10thDay
16%9%47%6%35%6%6%8%32%
2060
11th to 20thDay
17%9%47%6%3446%6%34%
2262
21st to endDay
19%8%36%4345%5%7%36%
2340
May1st to 10thDay
18%7%35%6%35%6%6%8%35%
2340
11th to 20thDay
16%8%45%5%35%5%5%7%37%
2314
21st to endDay
11%425%5%35%5%6%9%44%
2725
June1st to 10thDay
12%5%36%5%345%6%8%42%
2520
11th to 20thDay
11%5%25%6%35%6%7%9%40%
2549
21st to endDay
10%5%25%4245%7%10%45%
2700
July1st to 10thDay
8%3245%35%6%7%9%48%
2624
11th to 20thDay
10%5%25%435%5%7%11%42%
2361
21st to endDay
8%425%5%45%6%8%11%42%
2547
August1st to 10thDay
8%4235%35%6%8%10%44%
2327
11th to 20thDay
10%325%6%46%7%8%10%39%
2303
21st to endDay
10%6%35%5%345%6%9%44%
2520
September1st to 10thDay
12%5%25%5%46%5%6%9%43%
2134
11th to 20thDay
9%434435%5%6%9%47%
1980
21st to endDay
16%6%25%5%45%6%6%7%39%
1980
October1st to 10thDay
16%7%35%6%45%6%5%7%37%
1823
11th to 20thDay
20%9%37%6%46%5%5%7%29%
1800
21st to endDay
24%10%48%6%35%5%5%6%24%
1980
November1st to 10thDay
14%8%35%6%46%6%5%7%36%
1672
11th to 20thDay
17%11%47%5%445%6%7%30%
1544
21st to endDay
22%13%5%8%7%35%5%5%6%21%
1520
December1st to 10thDay
19%16%7%9%8%4445%6%19%
1520
11th to 20thDay
20%15%8%9%7%35%5%5%6%18%
1906
21st to endDay
30%18%6%7%6%34445%12%
2772
January1st to 10thNight
20%13%6%10%8%45%5%5%5%21%
2535
11th to 20thNight
22%18%6%9%6%44445%18%
2470
21st to endNight
15%14%7%12%8%45%45%6%22%
2599
February1st to 10thNight
18%14%5%10%8%45%45%6%21%
2340
11th to 20thNight
18%13%5%8%6%45%5%6%6%25%
2273
21st to endNight
20%11%5%8%6%345%5%7%25%
1793
March1st to 10thNight
16%8%5%7%6%45%6%6%7%32%
2000
11th to 20thNight
17%9%45%6%345%5%8%35%
1979
21st to endNight
17%11%37%5%345%45%34%
2178
April1st to 10thNight
19%8%46%435%5%5%7%34%
1900
11th to 20thNight
16%8%37%5%345%5%7%37%
1661
21st to endNight
16%6%37%5%35%5%5%7%37%
1620
May1st to 10thNight
18%7%37%5%346%6%8%34%
1620
11th to 20thNight
14%6%35%6%45%5%6%6%41%
1579
21st to endNight
11%5%33425%5%6%9%48%
1550
June1st to 10thNight
12%5%25%5%345%6%8%45%
1440
11th to 20thNight
10%5%25%5%35%5%6%11%43%
1401
21st to endNight
10%5%35%4335%6%9%47%
1260
July1st to 10thNight
7%42443445%8%55%
1327
11th to 20thNight
10%4245%345%6%10%48%
1594
21st to endNight
9%425%5%35%5%6%10%47%
1771
August1st to 10thNight
8%4146%35%6%7%9%47%
1611
11th to 20thNight
9%43443447%10%48%
1598
21st to endNight
10%425%5%35%45%9%48%
1818
September1st to 10thNight
10%6%36%4345%6%8%45%
1822
11th to 20thNight
11%4243345%6%7%52%
1980
21st to endNight
15%5%26%6%445%5%7%41%
1980
October1st to 10thNight
15%6%26%5%345%5%7%42%
2137
11th to 20thNight
19%9%37%6%3445%6%34%
2160
21st to endNight
24%9%37%6%335%5%6%29%
2376
November1st to 10thNight
17%6%26%5%25%47%6%40%
2403
11th to 20thNight
17%9%47%7%45%6%6%7%28%
2635
21st to endNight
22%13%46%6%35%5%5%7%24%
2660
December1st to 10thNight
23%14%5%8%6%35%45%7%20%
2660
11th to 20thNight
18%17%7%9%7%3445%6%21%
3288
21st to endNight
29%18%6%8%6%3444414%
4884

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
43%42%6%7%2
1627
11th to 20thDay
47%41%5%5%2
1710
21st to endDay
47%39%7%5%3
1791
February1st to 10thDay
44%38%8%8%2
1620
11th to 20thDay
41%38%8%8%4
1582
21st to endDay
43%38%8%9%21
1462
March1st to 10thDay
35%38%10%13%3
1948
11th to 20thDay
35%38%8%11%6%1
1980
21st to endDay
37%37%8%13%5%1
2178
April1st to 10thDay
29%38%10%13%10%1
2060
11th to 20thDay
33%36%9%13%9%1
2262
21st to endDay
31%38%8%13%8%1
2340
May1st to 10thDay
28%38%10%13%9%1
2340
11th to 20thDay
28%39%7%12%12%2
2318
21st to endDay
22%39%12%15%11%2
2725
June1st to 10thDay
25%39%10%16%8%1
2520
11th to 20thDay
22%39%12%16%10%1
2549
21st to endDay
23%38%11%18%9%1
2700
July1st to 10thDay
21%40%9%18%11%1
2554
11th to 20thDay
22%40%13%16%8%1
2290
21st to endDay
21%42%12%16%9%1
2405
August1st to 10thDay
21%40%11%19%9%
2314
11th to 20thDay
20%40%12%16%9%1
2303
21st to endDay
24%38%11%16%10%1
2520
September1st to 10thDay
25%39%10%16%9%1
2134
11th to 20thDay
22%39%12%19%8%
1980
21st to endDay
31%39%8%15%6%1
1980
October1st to 10thDay
29%39%10%13%8%1
1823
11th to 20thDay
38%39%10%10%4
1800
21st to endDay
40%39%8%9%4
1980
November1st to 10thDay
27%45%8%14%6%1
1672
11th to 20thDay
32%42%11%9%5%
1544
21st to endDay
41%43%6%9%2
1520
December1st to 10thDay
44%43%6%6%1
1520
11th to 20thDay
48%36%8%5%2
1906
21st to endDay
60%29%7%4
2772
January1st to 10thNight
45%42%5%6%2
2535
11th to 20thNight
46%42%6%5%2
2470
21st to endNight
44%39%6%8%3
2599
February1st to 10thNight
44%39%7%8%3
2340
11th to 20thNight
40%40%7%9%3
2275
21st to endNight
40%37%8%11%4
1793
March1st to 10thNight
33%39%8%15%6%
2010
11th to 20thNight
32%37%8%14%7%1
1980
21st to endNight
35%37%6%14%6%1
2178
April1st to 10thNight
31%37%8%13%10%2
1900
11th to 20thNight
31%36%7%14%11%1
1661
21st to endNight
32%38%6%12%10%2
1620
May1st to 10thNight
30%38%6%14%9%3
1620
11th to 20thNight
27%37%7%14%11%4
1580
21st to endNight
20%38%9%17%13%2
1551
June1st to 10thNight
24%39%9%15%10%2
1440
11th to 20thNight
23%38%10%14%14%1
1401
21st to endNight
24%38%9%18%11%1
1260
July1st to 10thNight
21%39%6%17%13%3
1289
11th to 20thNight
22%38%8%18%11%2
1542
21st to endNight
20%41%11%15%12%2
1672
August1st to 10thNight
23%40%8%20%8%1
1600
11th to 20thNight
19%38%11%20%12%1
1598
21st to endNight
21%38%9%19%11%2
1818
September1st to 10thNight
26%38%8%17%9%2
1822
11th to 20thNight
22%38%8%21%10%
1980
21st to endNight
32%38%6%15%8%
1980
October1st to 10thNight
28%39%7%16%9%1
2137
11th to 20thNight
36%38%7%13%6%
2160
21st to endNight
37%39%8%10%5%1
2376
November1st to 10thNight
23%44%8%17%8%
2403
11th to 20thNight
35%44%7%9%5%1
2635
21st to endNight
38%43%9%8%2
2660
December1st to 10thNight
45%43%6%5%1
2660
11th to 20thNight
48%36%8%6%1
3288
21st to endNight
62%28%7%21
4884

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
26%18%32%16%7%2
231
11th to 20thDay
26%15%38%14%5%1
270
21st to endDay
24%18%34%19%41
267
February1st to 10thDay
24%18%45%13%1
240
11th to 20thDay
25%23%38%14%1
240
21st to endDay
27%25%37%10%2
198
March1st to 10thDay
23%13%32%23%7%1
388
11th to 20thDay
22%13%35%23%5%1
420
21st to endDay
30%12%30%20%6%1
462
April1st to 10thDay
18%19%34%22%7%1
420
11th to 20thDay
24%13%29%20%10%4
412
21st to endDay
23%9%33%23%9%3
420
May1st to 10thDay
26%10%29%21%11%4
423
11th to 20thDay
20%9%24%28%15%5%
447
21st to endDay
14%5%21%32%23%6%
485
June1st to 10thDay
13%432%34%15%2
450
11th to 20thDay
13%9%23%32%19%4
479
21st to endDay
13%5%28%35%15%4
630
July1st to 10thDay
8%321%31%27%11%
549
11th to 20thDay
15%321%32%19%10%
444
21st to endDay
10%221%37%23%7%
488
August1st to 10thDay
7%219%33%24%14%
446
11th to 20thDay
12%414%35%23%11%
439
21st to endDay
13%318%34%23%10%
495
September1st to 10thDay
13%420%30%21%12%
450
11th to 20thDay
7%5%17%28%30%13%
450
21st to endDay
16%9%23%30%15%8%
450
October1st to 10thDay
20%8%24%24%20%6%
450
11th to 20thDay
19%17%30%25%7%2
450
21st to endDay
27%12%31%22%7%
495
November1st to 10thDay
17%17%34%19%9%3
270
11th to 20thDay
26%21%28%17%7%2
192
21st to endDay
28%17%34%18%3
180
December1st to 10thDay
29%17%32%16%6%1
180
11th to 20thDay
27%21%33%16%3
180
21st to endDay
29%21%30%17%4
198
January1st to 10thNight
25%17%36%15%7%
760
11th to 20thNight
30%14%32%21%3
760
21st to endNight
21%12%36%24%6%
800
February1st to 10thNight
26%15%35%22%3
720
11th to 20thNight
24%13%34%25%4
703
21st to endNight
26%12%38%21%3
592
March1st to 10thNight
20%9%37%26%7%
720
11th to 20thNight
20%8%37%27%8%
720
21st to endNight
22%8%30%28%10%1
792
April1st to 10thNight
23%10%33%28%6%1
720
11th to 20thNight
21%9%31%28%9%1
597
21st to endNight
18%5%32%35%9%1
540
May1st to 10thNight
21%427%31%15%2
540
11th to 20thNight
17%425%40%13%2
518
21st to endNight
12%322%36%23%3
389
June1st to 10thNight
15%126%40%16%1
360
11th to 20thNight
13%225%41%19%
360
21st to endNight
13%421%42%19%1
360
July1st to 10thNight
7%317%41%27%4
350
11th to 20thNight
12%314%41%27%4
498
21st to endNight
9%216%45%25%3
591
August1st to 10thNight
9%212%42%31%4
537
11th to 20thNight
10%214%36%34%4
534
21st to endNight
10%316%40%27%4
630
September1st to 10thNight
15%417%34%25%5%
720
11th to 20thNight
12%314%36%30%5%
720
21st to endNight
16%5%23%30%20%6%
720
October1st to 10thNight
19%6%22%32%18%4
720
11th to 20thNight
21%12%29%27%10%1
720
21st to endNight
26%11%29%28%6%
792
November1st to 10thNight
19%11%27%29%13%1
740
11th to 20thNight
22%15%32%21%8%1
760
21st to endNight
28%12%31%23%7%
760
December1st to 10thNight
31%16%31%16%6%1
760
11th to 20thNight
25%16%35%19%4
760
21st to endNight
31%12%32%23%2
836
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