Sandbanks Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sandbanks Provincial Park clear sky chart from 2005-11-06 to 2026-05-17.

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	26% 12% 4 9% 5% 4 4 3 4 5% 23%	131653
	Night	24% 13% 4 10% 5% 4 4 3 4 5% 23%	131420
Transparency	Day	61% 6% 12% 15% 5% 1	135089
	Night	62% 6% 11% 15% 6% 1	136090
Seeing	Day	32% 9% 22% 24% 11% 2	19996
	Night	31% 11% 25% 23% 9% 1	27102

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	16% 19% 8% 17% 6% 4 3 3 3 3 16%	4690
	11th to 20th	Day	24% 14% 5% 15% 5% 5% 5% 3 4 4 16%	4681
	21st to end	Day	8% 12% 9% 21% 13% 7% 5% 3 4 3 16%	5157
February	1st to 10th	Day	20% 13% 5% 13% 10% 6% 6% 4 5% 4 14%	1715
	11th to 20th	Day	20% 15% 5% 12% 7% 6% 5% 4 6% 5% 15%	1956
	21st to end	Day	15% 12% 5% 11% 9% 6% 5% 3 4 5% 24%	1730
March	1st to 10th	Day	23% 11% 5% 11% 7% 5% 4 3 4 5% 22%	4574
	11th to 20th	Day	23% 19% 7% 10% 5% 5% 4 2 4 5% 16%	4746
	21st to end	Day	31% 12% 4 10% 4 3 4 3 5% 5% 18%	6103
April	1st to 10th	Day	25% 14% 5% 10% 5% 4 4 3 4 5% 21%	2520
	11th to 20th	Day	23% 12% 3 7% 4 4 3 3 4 6% 30%	2548
	21st to end	Day	29% 11% 3 6% 3 4 3 3 3 4 30%	2730
May	1st to 10th	Day	30% 13% 3 7% 4 4 3 3 4 4 25%	6430
	11th to 20th	Day	22% 11% 3 7% 4 5% 5% 3 5% 6% 29%	6402
	21st to end	Day	25% 14% 4 7% 4 4 4 3 5% 6% 24%	6948
June	1st to 10th	Day	36% 11% 4 6% 3 3 3 3 4 6% 22%	2950
	11th to 20th	Day	26% 9% 3 6% 5% 4 5% 3 5% 7% 28%	3000
	21st to end	Day	42% 10% 3 7% 4 3 2 3 4 5% 18%	2967
July	1st to 10th	Day	35% 14% 3 8% 4 4 4 3 4 4 17%	6360
	11th to 20th	Day	31% 12% 3 8% 4 3 3 2 4 4 24%	6360
	21st to end	Day	28% 9% 3 5% 4 4 4 3 4 6% 32%	6927
August	1st to 10th	Day	27% 10% 3 7% 5% 4 4 4 5% 8% 23%	4564
	11th to 20th	Day	26% 10% 3 6% 4 4 4 3 5% 7% 28%	4288
	21st to end	Day	25% 7% 3 7% 4 3 4 4 5% 6% 33%	4364
September	1st to 10th	Day	27% 7% 2 5% 4 4 4 3 5% 7% 32%	2400
	11th to 20th	Day	27% 7% 2 5% 3 4 4 3 5% 7% 32%	2281
	21st to end	Day	25% 7% 2 6% 4 3 4 4 4 6% 35%	2200
October	1st to 10th	Day	23% 7% 2 5% 4 4 4 3 6% 7% 34%	2110
	11th to 20th	Day	27% 8% 3 6% 4 4 3 3 4 7% 30%	1878
	21st to end	Day	26% 11% 4 7% 5% 5% 4 4 6% 7% 24%	1980
November	1st to 10th	Day	29% 13% 4 9% 4 4 4 4 4 6% 20%	1850
	11th to 20th	Day	28% 15% 4 9% 6% 4 4 3 4 5% 19%	1778
	21st to end	Day	24% 15% 4 9% 5% 4 3 3 6% 7% 19%	1580
December	1st to 10th	Day	17% 17% 4 10% 6% 6% 6% 4 6% 7% 18%	2360
	11th to 20th	Day	31% 14% 4 8% 5% 4 4 4 5% 4 17%	2698
	21st to end	Day	21% 14% 3 9% 5% 5% 5% 4 5% 6% 24%	3828
January	1st to 10th	Night	17% 18% 8% 14% 6% 5% 4 3 4 4 16%	8234
	11th to 20th	Night	23% 15% 6% 17% 5% 4 4 3 4 5% 14%	8234
	21st to end	Night	8% 12% 8% 18% 10% 7% 5% 4 4 4 19%	9056
February	1st to 10th	Night	20% 14% 5% 12% 8% 6% 4 3 5% 6% 17%	2903
	11th to 20th	Night	18% 17% 5% 13% 8% 5% 5% 4 4 6% 16%	2549
	21st to end	Night	13% 14% 4 12% 7% 5% 5% 4 6% 6% 25%	2076
March	1st to 10th	Night	21% 12% 4 12% 8% 5% 4 3 4 5% 22%	5486
	11th to 20th	Night	21% 17% 5% 10% 5% 4 4 3 4 4 22%	5429
	21st to end	Night	26% 13% 6% 11% 5% 4 5% 4 5% 5% 18%	5071
April	1st to 10th	Night	27% 14% 4 6% 3 5% 3 3 4 5% 24%	2100
	11th to 20th	Night	23% 11% 3 7% 5% 4 5% 3 4 5% 29%	2021
	21st to end	Night	27% 11% 4 7% 4 3 4 3 4 5% 28%	1890
May	1st to 10th	Night	26% 14% 3 7% 4 4 4 3 4 5% 25%	3747
	11th to 20th	Night	26% 11% 3 7% 5% 4 4 3 5% 5% 27%	3645
	21st to end	Night	30% 13% 3 6% 4 3 3 2 3 6% 26%	3948
June	1st to 10th	Night	38% 12% 3 6% 5% 3 3 1 3 4 21%	1445
	11th to 20th	Night	25% 11% 3 6% 5% 4 3 3 4 7% 29%	1400
	21st to end	Night	39% 13% 3 6% 4 3 3 2 4 4 20%	1427
July	1st to 10th	Night	41% 14% 3 7% 3 3 3 3 3 4 15%	3619
	11th to 20th	Night	33% 13% 3 7% 3 3 3 2 3 4 27%	3620
	21st to end	Night	30% 10% 3 5% 3 3 3 3 4 6% 32%	3948
August	1st to 10th	Night	27% 9% 3 6% 5% 4 3 4 6% 7% 27%	2596
	11th to 20th	Night	26% 10% 3 7% 4 3 4 3 5% 5% 29%	2768
	21st to end	Night	27% 8% 2 5% 3 2 3 2 4 6% 37%	3520
September	1st to 10th	Night	27% 7% 2 6% 4 3 4 3 5% 6% 35%	2000
	11th to 20th	Night	28% 7% 2 5% 3 3 4 3 4 5% 37%	2118
	21st to end	Night	25% 6% 2 5% 4 3 4 3 5% 6% 38%	2200
October	1st to 10th	Night	21% 6% 2 6% 4 4 5% 4 5% 6% 36%	2289
	11th to 20th	Night	27% 8% 3 6% 4 4 4 3 5% 5% 33%	2521
	21st to end	Night	26% 11% 3 7% 4 5% 3 4 5% 6% 26%	2860
November	1st to 10th	Night	28% 11% 3 7% 5% 4 4 4 6% 6% 23%	2668
	11th to 20th	Night	31% 14% 3 8% 4 4 4 3 4 6% 18%	2840
	21st to end	Night	27% 16% 4 8% 4 4 4 3 5% 5% 19%	3036
December	1st to 10th	Night	20% 15% 5% 10% 6% 5% 5% 4 6% 6% 19%	5050
	11th to 20th	Night	30% 13% 4 9% 6% 4 3 3 4 5% 19%	5731
	21st to end	Night	20% 13% 5% 10% 7% 5% 5% 3 5% 6% 21%	7375

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	73% 4 7% 11% 4	4691
	11th to 20th	Day	69% 6% 10% 12% 3	4710
	21st to end	Day	73% 7% 6% 8% 4 3	5157
February	1st to 10th	Day	73% 6% 11% 7% 3	1715
	11th to 20th	Day	68% 6% 11% 10% 3 1	1964
	21st to end	Day	62% 5% 11% 15% 6% 1	1730
March	1st to 10th	Day	63% 4 11% 11% 9% 1	4578
	11th to 20th	Day	69% 7% 8% 10% 6% 1	4746
	21st to end	Day	67% 5% 7% 14% 7% 1	6103
April	1st to 10th	Day	64% 6% 9% 12% 7% 2	2520
	11th to 20th	Day	54% 6% 9% 19% 10% 1	2548
	21st to end	Day	57% 6% 11% 16% 9% 1	2730
May	1st to 10th	Day	60% 7% 11% 16% 5%	6442
	11th to 20th	Day	54% 7% 14% 17% 8% 1	6406
	21st to end	Day	59% 7% 11% 19% 4	6948
June	1st to 10th	Day	65% 5% 9% 15% 6%	2950
	11th to 20th	Day	55% 8% 14% 18% 5% 1	3000
	21st to end	Day	71% 5% 9% 10% 5% 1	2967
July	1st to 10th	Day	71% 5% 7% 13% 4	6290
	11th to 20th	Day	65% 5% 9% 16% 4	6284
	21st to end	Day	54% 6% 17% 18% 5%	6730
August	1st to 10th	Day	59% 7% 16% 14% 4	4550
	11th to 20th	Day	54% 8% 17% 16% 4	4330
	21st to end	Day	50% 6% 15% 25% 4	4364
September	1st to 10th	Day	50% 7% 13% 21% 9% 1	2400
	11th to 20th	Day	50% 6% 16% 20% 8% 1	2281
	21st to end	Day	48% 6% 16% 20% 9%	2200
October	1st to 10th	Day	46% 7% 15% 23% 8%	3435
	11th to 20th	Day	49% 6% 19% 18% 7% 2	3036
	21st to end	Day	53% 6% 11% 23% 6%	3191
November	1st to 10th	Day	64% 7% 12% 14% 4	1850
	11th to 20th	Day	67% 7% 12% 10% 5%	1778
	21st to end	Day	66% 7% 14% 9% 3	1580
December	1st to 10th	Day	64% 8% 10% 15% 3	2360
	11th to 20th	Day	69% 6% 13% 8% 3	2697
	21st to end	Day	61% 7% 14% 15% 4	3828
January	1st to 10th	Night	71% 7% 9% 9% 4	8234
	11th to 20th	Night	73% 5% 9% 10% 3	8280
	21st to end	Night	67% 6% 9% 7% 9% 3	9056
February	1st to 10th	Night	71% 5% 11% 9% 3	2903
	11th to 20th	Night	71% 6% 11% 9% 3	2552
	21st to end	Night	60% 6% 13% 15% 5% 1	2076
March	1st to 10th	Night	65% 6% 8% 13% 7% 1	5495
	11th to 20th	Night	65% 7% 10% 10% 7% 2	5430
	21st to end	Night	68% 4 7% 15% 6% 1	5071
April	1st to 10th	Night	60% 6% 9% 15% 9% 1	2100
	11th to 20th	Night	56% 6% 11% 16% 10% 1	2021
	21st to end	Night	59% 5% 10% 17% 9% 1	1890
May	1st to 10th	Night	59% 7% 11% 18% 5%	3752
	11th to 20th	Night	57% 8% 10% 20% 5%	3646
	21st to end	Night	60% 6% 8% 22% 4	3949
June	1st to 10th	Night	69% 4 6% 14% 7%	1445
	11th to 20th	Night	57% 5% 11% 21% 6%	1400
	21st to end	Night	68% 5% 7% 11% 8%	1427
July	1st to 10th	Night	73% 3 7% 12% 4	3581
	11th to 20th	Night	64% 3 8% 14% 11% 1	3572
	21st to end	Night	55% 5% 14% 22% 4	3831
August	1st to 10th	Night	55% 8% 14% 18% 4	2585
	11th to 20th	Night	56% 6% 15% 18% 4	2792
	21st to end	Night	49% 5% 14% 27% 5%	3519
September	1st to 10th	Night	50% 6% 13% 23% 8%	2000
	11th to 20th	Night	50% 6% 13% 20% 10% 1	2118
	21st to end	Night	46% 6% 15% 22% 11% 1	2200
October	1st to 10th	Night	45% 8% 14% 23% 9%	3744
	11th to 20th	Night	50% 5% 16% 21% 9%	4109
	21st to end	Night	55% 7% 14% 18% 6%	4610
November	1st to 10th	Night	61% 8% 14% 14% 3	2668
	11th to 20th	Night	68% 6% 11% 10% 4	2840
	21st to end	Night	67% 7% 14% 9% 4	3036
December	1st to 10th	Night	63% 7% 10% 15% 4	5050
	11th to 20th	Night	69% 6% 12% 10% 2	5733
	21st to end	Night	63% 7% 11% 14% 4	7375

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	27% 17% 33% 17% 5%	430
	11th to 20th	Day	31% 14% 30% 18% 6% 2	430
	21st to end	Day	21% 18% 34% 21% 6%	473
February	1st to 10th	Day	28% 16% 30% 19% 6% 1	430
	11th to 20th	Day	28% 18% 34% 17% 3 1	426
	21st to end	Day	21% 16% 28% 23% 10% 2	355
March	1st to 10th	Day	24% 20% 32% 19% 5%	430
	11th to 20th	Day	29% 13% 25% 22% 9% 3	434
	21st to end	Day	32% 14% 25% 20% 6% 3	594
April	1st to 10th	Day	33% 17% 27% 18% 5%	540
	11th to 20th	Day	28% 10% 25% 26% 9% 2	586
	21st to end	Day	32% 8% 24% 24% 9% 2	750
May	1st to 10th	Day	38% 5% 21% 26% 9% 2	753
	11th to 20th	Day	27% 5% 24% 25% 15% 3	754
	21st to end	Day	31% 8% 23% 25% 12% 1	790
June	1st to 10th	Day	43% 5% 14% 26% 11% 2	730
	11th to 20th	Day	31% 4 17% 31% 15% 2	730
	21st to end	Day	48% 5% 12% 24% 9% 2	730
July	1st to 10th	Day	40% 4 14% 27% 13% 2	720
	11th to 20th	Day	41% 4 11% 29% 13% 2	718
	21st to end	Day	41% 5% 12% 25% 14% 2	795
August	1st to 10th	Day	28% 3 14% 33% 19% 2	725
	11th to 20th	Day	33% 3 16% 26% 19% 3	717
	21st to end	Day	27% 5% 17% 31% 17% 3	622
September	1st to 10th	Day	27% 4 20% 30% 14% 4	530
	11th to 20th	Day	29% 7% 21% 28% 13% 3	464
	21st to end	Day	30% 7% 23% 27% 10% 3	420
October	1st to 10th	Day	22% 8% 29% 26% 15% 1	420
	11th to 20th	Day	32% 7% 24% 18% 15% 3	420
	21st to end	Day	30% 11% 26% 23% 9% 1	462
November	1st to 10th	Day	33% 17% 25% 21% 4 1	425
	11th to 20th	Day	34% 14% 25% 18% 7% 2	430
	21st to end	Day	36% 17% 26% 16% 5%	430
December	1st to 10th	Day	31% 15% 30% 15% 8%	430
	11th to 20th	Day	34% 20% 26% 15% 3 1	430
	21st to end	Day	29% 16% 28% 18% 8% 2	473
January	1st to 10th	Night	30% 17% 30% 18% 4 1	950
	11th to 20th	Night	31% 19% 27% 18% 5% 1	950
	21st to end	Night	22% 17% 33% 23% 4	1045
February	1st to 10th	Night	28% 18% 31% 17% 6%	931
	11th to 20th	Night	28% 16% 35% 17% 5%	823
	21st to end	Night	18% 15% 32% 26% 7% 2	692
March	1st to 10th	Night	23% 16% 35% 20% 5%	840
	11th to 20th	Night	28% 11% 30% 23% 8% 1	798
	21st to end	Night	28% 11% 32% 22% 7% 1	693
April	1st to 10th	Night	33% 12% 27% 21% 5% 1	630
	11th to 20th	Night	29% 10% 23% 30% 8% 1	624
	21st to end	Night	33% 7% 23% 27% 9% 1	630
May	1st to 10th	Night	32% 5% 22% 27% 13% 2	630
	11th to 20th	Night	33% 4 21% 29% 11% 2	611
	21st to end	Night	34% 4 21% 27% 12% 1	649
June	1st to 10th	Night	42% 6% 17% 26% 9% 1	600
	11th to 20th	Night	30% 5% 13% 32% 19% 2	600
	21st to end	Night	44% 3 14% 26% 13% 1	600
July	1st to 10th	Night	43% 2 11% 29% 14% 1	586
	11th to 20th	Night	43% 2 13% 27% 14% 1	582
	21st to end	Night	40% 3 11% 26% 19% 1	656
August	1st to 10th	Night	33% 2 12% 28% 22% 3	598
	11th to 20th	Night	31% 3 13% 30% 22% 2	592
	21st to end	Night	29% 4 17% 29% 19% 2	660
September	1st to 10th	Night	29% 7% 20% 29% 13% 2	600
	11th to 20th	Night	32% 6% 20% 31% 12% 1	600
	21st to end	Night	28% 5% 28% 26% 13%	600
October	1st to 10th	Night	24% 6% 30% 30% 10% 1	689
	11th to 20th	Night	30% 7% 26% 26% 11% 1	867
	21st to end	Night	30% 11% 27% 24% 7%	1001
November	1st to 10th	Night	32% 14% 27% 21% 6%	930
	11th to 20th	Night	40% 13% 22% 18% 6%	950
	21st to end	Night	37% 17% 27% 15% 5%	950
December	1st to 10th	Night	32% 17% 28% 17% 6%	950
	11th to 20th	Night	34% 20% 29% 14% 3	950
	21st to end	Night	28% 15% 30% 20% 6% 1	1045

Page generated at 2026-05-14 02:58:58. Version ac07

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