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 2025-01-22.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	15% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	105434
	Night	16% 11% 4 8% 5% 4 4 4 5% 7% 32%	103894
Transparency	Day	28% 46% 7% 12% 6% 1	109057
	Night	29% 45% 7% 12% 7% 1	108361
Seeing	Day	18% 10% 27% 26% 14% 5%	14993
	Night	20% 9% 28% 29% 13% 2	24369

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	18% 16% 8% 12% 6% 5% 4 3 4 4 21%	2777
	11th to 20th	Day	13% 21% 7% 19% 10% 7% 4 3 3 3 10%	2930
	21st to end	Day	24% 20% 6% 11% 5% 4 5% 3 4 4 15%	3133
February	1st to 10th	Day	17% 17% 5% 12% 5% 6% 4 4 5% 5% 20%	1710
	11th to 20th	Day	15% 13% 8% 12% 6% 5% 4 4 4 5% 24%	1663
	21st to end	Day	19% 13% 4 10% 6% 4 5% 4 5% 6% 24%	1551
March	1st to 10th	Day	22% 11% 4 10% 6% 5% 4 4 5% 5% 27%	3388
	11th to 20th	Day	12% 14% 4 9% 6% 4 4 3 5% 8% 31%	3480
	21st to end	Day	19% 8% 3 7% 5% 5% 5% 3 5% 6% 35%	3815
April	1st to 10th	Day	16% 10% 3 8% 5% 4 5% 4 6% 8% 31%	2175
	11th to 20th	Day	17% 9% 4 7% 5% 4 3 3 6% 6% 34%	2390
	21st to end	Day	19% 9% 3 7% 4 4 4 4 5% 7% 36%	2470
May	1st to 10th	Day	20% 7% 3 7% 5% 4 5% 4 5% 7% 32%	4108
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 4 5% 8% 33%	4108
	21st to end	Day	11% 4 2 6% 4 4 4 3 6% 9% 46%	4837
June	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 7% 8% 41%	2660
	11th to 20th	Day	10% 5% 2 6% 5% 4 4 5% 8% 9% 40%	2691
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 7% 10% 43%	2850
July	1st to 10th	Day	9% 4 2 5% 4 4 5% 4 7% 9% 45%	4614
	11th to 20th	Day	10% 5% 2 6% 4 3 5% 4 7% 10% 46%	4155
	21st to end	Day	7% 4 2 6% 4 5% 5% 5% 7% 10% 45%	4466
August	1st to 10th	Day	16% 5% 2 4 4 4 4 4 7% 9% 41%	4104
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 5% 8% 10% 37%	4044
	21st to end	Day	9% 6% 2 6% 5% 4 5% 4 6% 9% 44%	4436
September	1st to 10th	Day	11% 5% 2 6% 4 6% 5% 4 5% 9% 44%	2252
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 8% 48%	2090
	21st to end	Day	16% 6% 2 6% 4 5% 5% 4 6% 7% 38%	2090
October	1st to 10th	Day	15% 7% 2 6% 5% 5% 5% 4 5% 7% 38%	1924
	11th to 20th	Day	19% 9% 3 8% 4 5% 5% 4 6% 7% 30%	1900
	21st to end	Day	23% 10% 3 9% 5% 4 5% 4 5% 7% 25%	2090
November	1st to 10th	Day	14% 8% 2 7% 5% 6% 5% 4 6% 7% 36%	1762
	11th to 20th	Day	17% 12% 4 8% 5% 4 5% 3 6% 7% 30%	1625
	21st to end	Day	21% 14% 5% 9% 6% 5% 4 4 6% 6% 19%	1600
December	1st to 10th	Day	20% 17% 5% 11% 6% 5% 4 4 6% 6% 16%	2600
	11th to 20th	Day	23% 17% 5% 10% 6% 5% 4 3 5% 5% 17%	2986
	21st to end	Day	28% 19% 5% 9% 5% 4 4 4 4 5% 13%	3960
January	1st to 10th	Night	18% 17% 7% 10% 5% 5% 4 3 4 5% 20%	4371
	11th to 20th	Night	17% 19% 7% 14% 7% 11% 4 3 4 4 12%	4250
	21st to end	Night	25% 18% 7% 15% 5% 4 3 2 4 4 13%	4546
February	1st to 10th	Night	17% 16% 4 10% 7% 5% 5% 3 5% 5% 22%	2470
	11th to 20th	Night	16% 14% 4 9% 5% 5% 4 4 6% 6% 25%	2403
	21st to end	Night	19% 12% 4 9% 6% 5% 4 4 5% 7% 24%	1902
March	1st to 10th	Night	20% 10% 4 7% 6% 4 4 3 4 6% 32%	3450
	11th to 20th	Night	13% 10% 3 6% 5% 4 4 4 5% 8% 38%	3479
	21st to end	Night	16% 11% 3 7% 4 4 4 4 4 5% 39%	3817
April	1st to 10th	Night	20% 9% 3 7% 4 4 4 4 5% 6% 33%	2005
	11th to 20th	Night	17% 8% 3 8% 5% 4 4 4 5% 7% 36%	1754
	21st to end	Night	16% 6% 2 8% 5% 5% 5% 4 5% 7% 36%	1710
May	1st to 10th	Night	21% 8% 2 7% 4 3 3 3 5% 6% 37%	2833
	11th to 20th	Night	12% 7% 3 8% 6% 6% 6% 4 6% 6% 37%	2785
	21st to end	Night	12% 4 2 4 4 3 4 4 6% 9% 48%	2738
June	1st to 10th	Night	12% 6% 2 5% 5% 4 4 4 6% 8% 44%	1520
	11th to 20th	Night	10% 5% 2 5% 4 5% 5% 4 7% 10% 42%	1478
	21st to end	Night	10% 5% 2 6% 3 4 4 4 6% 9% 46%	1330
July	1st to 10th	Night	8% 4 2 5% 4 4 3 4 6% 10% 50%	2329
	11th to 20th	Night	9% 4 2 5% 4 4 3 4 6% 9% 50%	2800
	21st to end	Night	6% 4 2 6% 4 4 5% 5% 6% 9% 49%	3087
August	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	2825
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 9% 47%	2785
	21st to end	Night	9% 4 2 6% 5% 4 4 4 6% 8% 49%	3188
September	1st to 10th	Night	10% 6% 2 6% 3 4 5% 4 6% 7% 46%	1924
	11th to 20th	Night	10% 4 1 4 3 4 4 4 6% 6% 53%	2090
	21st to end	Night	16% 5% 2 7% 5% 5% 5% 4 5% 7% 39%	2090
October	1st to 10th	Night	15% 6% 2 6% 4 4 4 4 6% 7% 43%	2256
	11th to 20th	Night	18% 9% 3 8% 4 5% 4 3 6% 6% 35%	2280
	21st to end	Night	22% 9% 3 7% 5% 4 4 4 6% 6% 30%	2508
November	1st to 10th	Night	17% 6% 2 6% 4 4 4 3 7% 6% 40%	2533
	11th to 20th	Night	17% 10% 3 8% 6% 5% 5% 4 6% 7% 28%	2774
	21st to end	Night	22% 14% 4 7% 6% 5% 5% 4 5% 7% 23%	2800
December	1st to 10th	Night	17% 16% 5% 12% 6% 5% 5% 4 5% 7% 17%	4580
	11th to 20th	Night	20% 19% 6% 11% 6% 4 4 3 4 5% 20%	5208
	21st to end	Night	26% 18% 5% 10% 5% 4 4 3 5% 5% 16%	6996

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	45% 40% 4 6% 5%	2778
	11th to 20th	Day	53% 39% 3 3 2	2930
	21st to end	Day	47% 42% 6% 3 2	3133
February	1st to 10th	Day	24% 65% 3 5% 2	1710
	11th to 20th	Day	23% 64% 2 8% 3	1672
	21st to end	Day	21% 66% 4 6% 3 1	1551
March	1st to 10th	Day	38% 43% 3 13% 2	3391
	11th to 20th	Day	30% 41% 14% 11% 3	3480
	21st to end	Day	28% 42% 8% 13% 8% 1	3815
April	1st to 10th	Day	22% 65% 3 6% 3	2175
	11th to 20th	Day	18% 66% 3 8% 4 1	2390
	21st to end	Day	19% 66% 4 6% 5% 1	2470
May	1st to 10th	Day	32% 42% 9% 11% 5% 2	4120
	11th to 20th	Day	30% 46% 11% 11% 1	4112
	21st to end	Day	21% 43% 7% 13% 12% 4	4837
June	1st to 10th	Day	15% 66% 4 9% 6% 1	2660
	11th to 20th	Day	15% 66% 5% 7% 6% 1	2691
	21st to end	Day	13% 64% 5% 10% 8%	2850
July	1st to 10th	Day	24% 37% 9% 18% 10% 2	4544
	11th to 20th	Day	20% 37% 10% 24% 9%	4084
	21st to end	Day	20% 38% 12% 15% 14% 1	4324
August	1st to 10th	Day	27% 38% 10% 15% 9% 1	4091
	11th to 20th	Day	27% 40% 10% 19% 4	4083
	21st to end	Day	23% 39% 8% 21% 8%	4436
September	1st to 10th	Day	14% 60% 7% 12% 6%	2252
	11th to 20th	Day	13% 61% 5% 12% 9%	2090
	21st to end	Day	18% 60% 6% 11% 6%	2090
October	1st to 10th	Day	22% 39% 10% 16% 14% 1	3197
	11th to 20th	Day	20% 37% 10% 20% 13%	3140
	21st to end	Day	27% 37% 12% 19% 4	3428
November	1st to 10th	Day	25% 56% 6% 9% 3 1	1762
	11th to 20th	Day	23% 57% 6% 9% 5%	1625
	21st to end	Day	29% 58% 7% 5% 2	1600
December	1st to 10th	Day	44% 38% 9% 7% 2	2600
	11th to 20th	Day	48% 33% 8% 6% 5%	2986
	21st to end	Day	55% 30% 6% 7% 2	3960
January	1st to 10th	Night	42% 42% 6% 7% 2	4371
	11th to 20th	Night	48% 43% 3 4 1	4250
	21st to end	Night	51% 40% 4 4 1	4546
February	1st to 10th	Night	22% 65% 4 6% 2	2470
	11th to 20th	Night	20% 64% 4 8% 4	2405
	21st to end	Night	21% 65% 3 6% 3 1	1902
March	1st to 10th	Night	34% 42% 8% 12% 5%	3460
	11th to 20th	Night	25% 42% 13% 12% 8% 1	3480
	21st to end	Night	26% 42% 9% 11% 11% 1	3817
April	1st to 10th	Night	21% 65% 3 7% 3	2005
	11th to 20th	Night	18% 66% 3 7% 5% 1	1754
	21st to end	Night	15% 65% 4 9% 5% 1	1710
May	1st to 10th	Night	29% 41% 7% 11% 8% 3	2840
	11th to 20th	Night	29% 44% 9% 14% 3	2786
	21st to end	Night	20% 41% 8% 13% 16% 2	2739
June	1st to 10th	Night	14% 64% 4 11% 6% 1	1520
	11th to 20th	Night	13% 65% 5% 11% 5% 1	1478
	21st to end	Night	13% 64% 5% 9% 8%	1330
July	1st to 10th	Night	20% 37% 9% 18% 12% 5%	2291
	11th to 20th	Night	20% 37% 9% 23% 10% 1	2748
	21st to end	Night	21% 38% 11% 14% 14% 2	2988
August	1st to 10th	Night	25% 38% 8% 16% 11% 2	2814
	11th to 20th	Night	25% 38% 11% 21% 5%	2812
	21st to end	Night	21% 39% 8% 22% 10%	3188
September	1st to 10th	Night	13% 60% 6% 12% 9%	1924
	11th to 20th	Night	11% 60% 4 13% 11% 1	2090
	21st to end	Night	18% 60% 5% 12% 6%	2090
October	1st to 10th	Night	16% 38% 4 22% 19% 1	3763
	11th to 20th	Night	25% 37% 9% 17% 12%	3779
	21st to end	Night	21% 37% 12% 20% 10%	4120
November	1st to 10th	Night	23% 56% 5% 9% 6%	2533
	11th to 20th	Night	21% 57% 5% 12% 5%	2774
	21st to end	Night	27% 58% 7% 6% 2	2800
December	1st to 10th	Night	41% 38% 11% 8% 2	4580
	11th to 20th	Night	45% 34% 6% 10% 5%	5208
	21st to end	Night	52% 28% 8% 8% 4	6996

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	25% 18% 33% 16% 6% 2	257
	11th to 20th	Day	26% 17% 37% 14% 5% 1	300
	21st to end	Day	26% 17% 33% 19% 4 1	300
February	1st to 10th	Day	22% 17% 42% 14% 4	270
	11th to 20th	Day	25% 22% 37% 15% 1	270
	21st to end	Day	27% 24% 38% 10% 1	225
March	1st to 10th	Day	24% 13% 32% 23% 7% 1	427
	11th to 20th	Day	22% 14% 35% 23% 4 1	460
	21st to end	Day	29% 13% 32% 19% 6% 1	506
April	1st to 10th	Day	18% 18% 33% 23% 6% 1	460
	11th to 20th	Day	25% 14% 29% 20% 9% 4	452
	21st to end	Day	23% 9% 34% 23% 8% 3	460
May	1st to 10th	Day	24% 10% 28% 23% 11% 4	463
	11th to 20th	Day	19% 9% 24% 28% 16% 5%	487
	21st to end	Day	13% 6% 22% 32% 22% 6%	529
June	1st to 10th	Day	13% 6% 31% 32% 15% 3	490
	11th to 20th	Day	12% 9% 23% 33% 19% 4	521
	21st to end	Day	14% 6% 29% 34% 14% 3	680
July	1st to 10th	Day	8% 4 21% 31% 26% 10%	594
	11th to 20th	Day	15% 4 22% 31% 18% 10%	484
	21st to end	Day	10% 2 20% 36% 23% 8%	532
August	1st to 10th	Day	9% 4 20% 33% 22% 13%	486
	11th to 20th	Day	12% 4 16% 34% 22% 11%	479
	21st to end	Day	13% 3 17% 34% 23% 10%	539
September	1st to 10th	Day	12% 4 21% 29% 21% 12%	490
	11th to 20th	Day	7% 5% 16% 27% 31% 15%	490
	21st to end	Day	16% 10% 22% 30% 15% 7%	490
October	1st to 10th	Day	18% 8% 23% 25% 19% 6%	490
	11th to 20th	Day	18% 16% 30% 26% 8% 3	490
	21st to end	Day	25% 13% 31% 22% 8%	539
November	1st to 10th	Day	17% 18% 35% 19% 8% 3	300
	11th to 20th	Day	25% 21% 29% 17% 7% 1	213
	21st to end	Day	29% 17% 35% 17% 3	200
December	1st to 10th	Day	30% 16% 31% 18% 5% 1	200
	11th to 20th	Day	30% 19% 32% 17% 3	200
	21st to end	Day	30% 19% 30% 17% 4	220
January	1st to 10th	Night	25% 17% 36% 16% 7%	800
	11th to 20th	Night	29% 15% 33% 21% 3	800
	21st to end	Night	23% 13% 35% 24% 6%	841
February	1st to 10th	Night	25% 15% 34% 23% 3	760
	11th to 20th	Night	23% 13% 34% 26% 4	743
	21st to end	Night	25% 12% 37% 22% 3	628
March	1st to 10th	Night	21% 9% 36% 26% 8%	760
	11th to 20th	Night	20% 8% 38% 26% 7%	760
	21st to end	Night	22% 9% 31% 28% 9% 1	836
April	1st to 10th	Night	23% 10% 34% 27% 6% 1	760
	11th to 20th	Night	22% 9% 31% 28% 9% 1	630
	21st to end	Night	18% 6% 31% 35% 9% 1	570
May	1st to 10th	Night	22% 4 26% 32% 15% 2	570
	11th to 20th	Night	16% 4 24% 41% 13% 2	547
	21st to end	Night	13% 3 23% 36% 22% 3	411
June	1st to 10th	Night	15% 1 27% 40% 16% 1	380
	11th to 20th	Night	12% 3 24% 42% 20%	380
	21st to end	Night	13% 4 21% 41% 19% 1	380
July	1st to 10th	Night	7% 3 18% 42% 26% 4	370
	11th to 20th	Night	12% 3 14% 41% 28% 4	527
	21st to end	Night	8% 2 16% 45% 26% 3	624
August	1st to 10th	Night	9% 2 14% 41% 30% 4	567
	11th to 20th	Night	11% 2 14% 35% 34% 4	564
	21st to end	Night	9% 3 16% 40% 28% 4	665
September	1st to 10th	Night	14% 4 18% 33% 26% 5%	760
	11th to 20th	Night	11% 3 14% 35% 32% 5%	760
	21st to end	Night	17% 5% 22% 31% 19% 5%	760
October	1st to 10th	Night	18% 7% 23% 31% 18% 3	760
	11th to 20th	Night	20% 12% 28% 27% 11% 2	760
	21st to end	Night	25% 11% 29% 28% 6%	836
November	1st to 10th	Night	19% 12% 28% 28% 12% 1	780
	11th to 20th	Night	22% 15% 32% 22% 8% 1	800
	21st to end	Night	28% 12% 31% 23% 6%	800
December	1st to 10th	Night	30% 16% 31% 17% 6% 1	800
	11th to 20th	Night	26% 17% 34% 19% 4	800
	21st to end	Night	30% 12% 32% 24% 2	880

Page generated at 2025-01-19 03:06:48. Version ac07

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