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 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	26% 12% 4 8% 5% 4 4 3 4 6% 24%	104889
	Night	25% 12% 4 9% 5% 4 4 3 4 5% 24%	104615
Transparency	Day	60% 7% 13% 15% 5% 1	108343
	Night	61% 7% 12% 15% 5% 1	109268
Seeing	Day	32% 9% 22% 24% 10% 2	18164
	Night	32% 10% 25% 23% 9% 1	25307

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	13% 15% 10% 13% 8% 5% 4 3 4 4 23%	2606
	11th to 20th	Day	19% 14% 5% 16% 6% 6% 5% 3 4 5% 16%	2610
	21st to end	Day	11% 14% 8% 13% 7% 6% 5% 4 4 4 24%	2791
February	1st to 10th	Day	21% 14% 5% 13% 9% 5% 6% 4 5% 5% 14%	1551
	11th to 20th	Day	21% 15% 5% 11% 7% 6% 5% 4 6% 5% 16%	1764
	21st to end	Day	14% 12% 6% 12% 9% 6% 5% 4 4 5% 25%	1570
March	1st to 10th	Day	21% 12% 4 8% 6% 4 4 3 3 6% 29%	3114
	11th to 20th	Day	21% 19% 7% 13% 7% 5% 5% 3 3 4 13%	3242
	21st to end	Day	29% 13% 5% 11% 5% 3 3 3 5% 6% 17%	4167
April	1st to 10th	Day	25% 14% 5% 11% 6% 4 4 3 4 6% 19%	2280
	11th to 20th	Day	23% 12% 3 6% 4 4 3 4 4 6% 30%	2302
	21st to end	Day	30% 12% 3 6% 3 4 3 3 3 3 30%	2470
May	1st to 10th	Day	24% 12% 4 8% 5% 4 4 3 5% 5% 25%	4385
	11th to 20th	Day	24% 11% 4 8% 4 4 5% 3 5% 6% 26%	4398
	21st to end	Day	28% 14% 4 7% 4 4 5% 3 5% 6% 19%	4836
June	1st to 10th	Day	36% 12% 4 7% 3 3 3 3 4 6% 21%	2802
	11th to 20th	Day	26% 9% 3 6% 5% 4 5% 3 5% 7% 28%	2850
	21st to end	Day	43% 11% 3 7% 4 3 2 3 4 5% 16%	2819
July	1st to 10th	Day	37% 13% 3 7% 4 3 4 2 4 4 19%	4440
	11th to 20th	Day	36% 14% 3 7% 4 3 3 2 4 4 19%	4440
	21st to end	Day	28% 8% 3 4 3 3 4 3 4 6% 35%	4815
August	1st to 10th	Day	28% 11% 3 7% 5% 4 4 4 5% 8% 21%	4424
	11th to 20th	Day	26% 10% 3 6% 4 4 4 3 5% 7% 27%	4154
	21st to end	Day	25% 7% 3 7% 4 3 4 4 5% 6% 33%	4230
September	1st to 10th	Day	27% 7% 2 5% 4 4 4 3 5% 7% 32%	2280
	11th to 20th	Day	27% 7% 2 5% 4 4 4 3 5% 7% 32%	2167
	21st to end	Day	26% 8% 2 6% 4 3 4 4 4 6% 34%	2090
October	1st to 10th	Day	23% 7% 2 5% 4 4 4 3 5% 7% 34%	2005
	11th to 20th	Day	28% 8% 3 5% 4 4 3 3 4 7% 29%	1784
	21st to end	Day	26% 10% 4 6% 5% 5% 4 4 6% 7% 24%	1881
November	1st to 10th	Day	29% 13% 3 9% 4 4 3 4 4 6% 21%	1760
	11th to 20th	Day	28% 15% 4 9% 6% 4 3 3 4 5% 20%	1694
	21st to end	Day	25% 15% 4 9% 5% 4 4 3 6% 7% 19%	1505
December	1st to 10th	Day	17% 17% 4 10% 6% 6% 6% 4 6% 7% 18%	2290
	11th to 20th	Day	31% 14% 4 8% 5% 4 4 4 5% 4 17%	2628
	21st to end	Day	21% 14% 3 9% 5% 5% 5% 3 5% 6% 24%	3745
January	1st to 10th	Night	14% 12% 8% 11% 7% 6% 5% 4 5% 5% 23%	4569
	11th to 20th	Night	21% 16% 6% 17% 5% 4 4 4 5% 5% 12%	4580
	21st to end	Night	12% 13% 8% 13% 6% 5% 5% 4 4 5% 24%	4899
February	1st to 10th	Night	22% 13% 5% 11% 7% 5% 4 3 5% 6% 18%	2627
	11th to 20th	Night	19% 17% 5% 12% 7% 5% 5% 4 4 6% 17%	2301
	21st to end	Night	13% 13% 4 12% 7% 5% 5% 4 5% 6% 26%	1884
March	1st to 10th	Night	20% 13% 4 10% 7% 5% 4 3 3 5% 27%	3726
	11th to 20th	Night	20% 18% 6% 12% 6% 4 4 3 4 5% 18%	3713
	21st to end	Night	27% 12% 6% 10% 4 4 4 3 4 4 20%	3465
April	1st to 10th	Night	27% 15% 4 6% 4 5% 3 3 4 5% 24%	1900
	11th to 20th	Night	22% 11% 3 8% 5% 4 5% 3 4 5% 30%	1827
	21st to end	Night	27% 11% 4 7% 4 3 3 3 4 5% 29%	1710
May	1st to 10th	Night	24% 12% 3 7% 5% 4 4 3 4 6% 29%	2562
	11th to 20th	Night	24% 11% 3 7% 5% 5% 5% 3 5% 6% 26%	2506
	21st to end	Night	34% 14% 3 6% 4 3 3 2 4 6% 22%	2749
June	1st to 10th	Night	38% 13% 3 6% 5% 3 3 1 3 4 20%	1373
	11th to 20th	Night	26% 11% 3 6% 5% 4 3 3 4 7% 28%	1330
	21st to end	Night	40% 13% 3 6% 3 3 3 2 4 4 20%	1355
July	1st to 10th	Night	43% 11% 3 6% 3 3 3 3 4 4 18%	2530
	11th to 20th	Night	37% 16% 3 7% 3 4 3 2 3 3 19%	2530
	21st to end	Night	27% 9% 3 6% 3 3 3 2 4 6% 36%	2750
August	1st to 10th	Night	28% 9% 3 6% 5% 4 3 4 6% 7% 26%	2516
	11th to 20th	Night	27% 11% 3 7% 4 3 4 3 5% 5% 28%	2682
	21st to end	Night	27% 8% 2 5% 3 2 3 2 4 6% 38%	3412
September	1st to 10th	Night	27% 6% 2 6% 4 3 4 3 5% 6% 34%	1900
	11th to 20th	Night	29% 7% 2 5% 3 3 4 3 4 5% 37%	2012
	21st to end	Night	26% 6% 2 5% 4 3 4 3 5% 6% 37%	2090
October	1st to 10th	Night	22% 6% 2 6% 4 4 5% 4 5% 6% 36%	2174
	11th to 20th	Night	28% 8% 3 6% 4 4 4 3 5% 5% 32%	2395
	21st to end	Night	26% 11% 3 7% 4 5% 3 4 5% 7% 26%	2717
November	1st to 10th	Night	28% 11% 3 7% 5% 4 4 4 6% 6% 23%	2538
	11th to 20th	Night	31% 14% 3 8% 5% 4 4 3 4 6% 19%	2705
	21st to end	Night	26% 16% 4 8% 5% 4 4 3 4 5% 20%	2891
December	1st to 10th	Night	20% 15% 5% 10% 6% 5% 5% 4 6% 6% 19%	4900
	11th to 20th	Night	30% 13% 4 9% 6% 4 3 3 4 5% 19%	5581
	21st to end	Night	20% 13% 5% 10% 7% 5% 5% 3 4 6% 21%	7216

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	66% 5% 9% 14% 5%	2607
	11th to 20th	Day	66% 9% 12% 10% 3	2610
	21st to end	Day	63% 8% 10% 9% 4 6%	2791
February	1st to 10th	Day	72% 6% 11% 7% 3	1551
	11th to 20th	Day	69% 6% 12% 9% 3 1	1772
	21st to end	Day	61% 6% 12% 15% 6% 1	1570
March	1st to 10th	Day	58% 4 14% 14% 10% 1	3118
	11th to 20th	Day	71% 9% 7% 8% 4	3242
	21st to end	Day	67% 6% 8% 14% 5% 1	4167
April	1st to 10th	Day	65% 7% 9% 11% 6% 2	2280
	11th to 20th	Day	53% 6% 9% 19% 11% 1	2302
	21st to end	Day	57% 6% 11% 16% 8% 1	2470
May	1st to 10th	Day	56% 10% 14% 15% 4	4400
	11th to 20th	Day	55% 9% 14% 16% 6% 1	4402
	21st to end	Day	62% 9% 11% 14% 4	4836
June	1st to 10th	Day	67% 5% 9% 13% 6%	2802
	11th to 20th	Day	54% 8% 15% 17% 6% 1	2850
	21st to end	Day	72% 5% 9% 9% 4 1	2819
July	1st to 10th	Day	69% 5% 9% 13% 5%	4370
	11th to 20th	Day	71% 5% 7% 13% 4	4364
	21st to end	Day	51% 6% 20% 17% 5%	4662
August	1st to 10th	Day	61% 8% 16% 13% 3	4410
	11th to 20th	Day	54% 8% 17% 16% 4	4196
	21st to end	Day	50% 6% 15% 25% 4	4230
September	1st to 10th	Day	50% 7% 14% 19% 9% 1	2280
	11th to 20th	Day	50% 7% 15% 20% 7% 1	2167
	21st to end	Day	49% 7% 16% 19% 9%	2090
October	1st to 10th	Day	46% 7% 15% 23% 8%	3330
	11th to 20th	Day	49% 6% 19% 17% 7% 2	2942
	21st to end	Day	53% 6% 11% 23% 6%	3092
November	1st to 10th	Day	63% 7% 12% 14% 4	1760
	11th to 20th	Day	66% 7% 12% 11% 5%	1694
	21st to end	Day	66% 7% 15% 9% 3	1505
December	1st to 10th	Day	63% 8% 10% 15% 3	2290
	11th to 20th	Day	69% 6% 14% 8% 3	2627
	21st to end	Day	61% 7% 14% 15% 4	3745
January	1st to 10th	Night	60% 10% 12% 11% 6% 1	4569
	11th to 20th	Night	73% 7% 12% 6% 3	4580
	21st to end	Night	61% 6% 13% 8% 7% 4	4899
February	1st to 10th	Night	71% 5% 11% 9% 3	2627
	11th to 20th	Night	71% 7% 12% 9% 2	2304
	21st to end	Night	60% 5% 14% 15% 5% 1	1884
March	1st to 10th	Night	61% 6% 10% 17% 6%	3735
	11th to 20th	Night	67% 8% 9% 11% 4	3714
	21st to end	Night	66% 5% 8% 14% 6% 1	3465
April	1st to 10th	Night	61% 6% 10% 14% 8% 1	1900
	11th to 20th	Night	56% 6% 11% 15% 11% 1	1827
	21st to end	Night	59% 5% 10% 16% 9% 1	1710
May	1st to 10th	Night	53% 9% 15% 18% 5%	2567
	11th to 20th	Night	57% 10% 12% 17% 5%	2507
	21st to end	Night	63% 7% 9% 16% 4	2750
June	1st to 10th	Night	71% 4 6% 13% 6%	1373
	11th to 20th	Night	57% 5% 11% 20% 6%	1330
	21st to end	Night	69% 5% 8% 10% 8%	1355
July	1st to 10th	Night	70% 4 9% 12% 4	2491
	11th to 20th	Night	71% 4 7% 10% 8%	2482
	21st to end	Night	50% 6% 16% 23% 6%	2663
August	1st to 10th	Night	56% 8% 15% 17% 3	2505
	11th to 20th	Night	57% 6% 15% 17% 4	2706
	21st to end	Night	49% 5% 14% 27% 5%	3411
September	1st to 10th	Night	50% 6% 13% 21% 9%	1900
	11th to 20th	Night	51% 6% 13% 19% 10% 1	2012
	21st to end	Night	47% 6% 15% 21% 10% 1	2090
October	1st to 10th	Night	45% 9% 14% 23% 9%	3629
	11th to 20th	Night	50% 5% 16% 21% 8%	3983
	21st to end	Night	55% 7% 14% 17% 7%	4467
November	1st to 10th	Night	60% 8% 14% 14% 3	2538
	11th to 20th	Night	67% 7% 11% 11% 4	2705
	21st to end	Night	67% 7% 14% 8% 4	2891
December	1st to 10th	Night	63% 8% 10% 15% 4	4900
	11th to 20th	Night	69% 6% 13% 10% 2	5583
	21st to end	Night	63% 7% 11% 14% 4	7216

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% 34% 17% 5% 1	400
	11th to 20th	Day	30% 14% 29% 19% 6% 2	400
	21st to end	Day	23% 16% 33% 21% 7%	410
February	1st to 10th	Day	30% 18% 31% 16% 5% 1	370
	11th to 20th	Day	29% 18% 34% 16% 2	366
	21st to end	Day	20% 16% 28% 23% 10% 2	307
March	1st to 10th	Day	23% 20% 32% 19% 5% 1	370
	11th to 20th	Day	28% 13% 25% 21% 9% 3	373
	21st to end	Day	31% 15% 24% 20% 6% 3	506
April	1st to 10th	Day	33% 16% 27% 18% 5%	460
	11th to 20th	Day	29% 10% 24% 25% 10% 2	500
	21st to end	Day	33% 8% 25% 25% 8% 1	650
May	1st to 10th	Day	36% 5% 22% 27% 9% 2	653
	11th to 20th	Day	25% 5% 24% 26% 16% 3	674
	21st to end	Day	31% 8% 23% 25% 12% 1	735
June	1st to 10th	Day	43% 5% 15% 25% 10% 1	680
	11th to 20th	Day	31% 4 18% 30% 15% 2	680
	21st to end	Day	49% 4 11% 24% 9% 3	680
July	1st to 10th	Day	40% 5% 15% 26% 13% 2	670
	11th to 20th	Day	42% 4 12% 28% 12% 2	668
	21st to end	Day	41% 5% 13% 24% 14% 2	740
August	1st to 10th	Day	30% 3 15% 32% 19% 1	675
	11th to 20th	Day	33% 3 16% 27% 19% 3	667
	21st to end	Day	28% 5% 17% 30% 17% 4	576
September	1st to 10th	Day	28% 4 21% 31% 13% 3	490
	11th to 20th	Day	29% 8% 21% 27% 12% 3	430
	21st to end	Day	31% 6% 23% 26% 10% 3	390
October	1st to 10th	Day	22% 8% 30% 25% 13% 1	390
	11th to 20th	Day	34% 8% 25% 17% 14% 3	390
	21st to end	Day	30% 11% 27% 23% 8% 1	429
November	1st to 10th	Day	32% 17% 25% 20% 4 1	395
	11th to 20th	Day	34% 14% 24% 19% 7% 2	400
	21st to end	Day	37% 16% 26% 16% 5%	400
December	1st to 10th	Day	31% 15% 30% 16% 8% 1	400
	11th to 20th	Day	34% 20% 26% 16% 4 1	400
	21st to end	Day	28% 17% 27% 18% 8% 2	440
January	1st to 10th	Night	30% 17% 30% 18% 4 1	900
	11th to 20th	Night	29% 18% 27% 18% 5% 1	900
	21st to end	Night	23% 14% 34% 24% 5%	941
February	1st to 10th	Night	29% 17% 31% 17% 5%	835
	11th to 20th	Night	28% 16% 36% 16% 4	743
	21st to end	Night	18% 15% 32% 26% 7% 2	628
March	1st to 10th	Night	23% 15% 36% 21% 5%	760
	11th to 20th	Night	27% 11% 30% 23% 8% 1	722
	21st to end	Night	28% 11% 31% 22% 7% 1	627
April	1st to 10th	Night	34% 11% 27% 21% 6% 1	570
	11th to 20th	Night	27% 10% 23% 30% 8% 1	564
	21st to end	Night	33% 7% 23% 28% 8% 1	570
May	1st to 10th	Night	31% 5% 21% 29% 13% 2	570
	11th to 20th	Night	33% 4 20% 29% 12% 2	562
	21st to end	Night	34% 5% 22% 27% 11% 1	616
June	1st to 10th	Night	43% 5% 17% 26% 8% 1	570
	11th to 20th	Night	30% 5% 13% 32% 18% 2	570
	21st to end	Night	44% 3 13% 25% 13% 1	570
July	1st to 10th	Night	43% 2 12% 29% 14% 1	556
	11th to 20th	Night	44% 2 13% 26% 14% 1	552
	21st to end	Night	40% 3 11% 26% 18% 1	623
August	1st to 10th	Night	34% 2 12% 28% 21% 2	568
	11th to 20th	Night	32% 3 12% 30% 21% 1	562
	21st to end	Night	29% 4 17% 28% 20% 2	627
September	1st to 10th	Night	29% 7% 21% 29% 12% 2	570
	11th to 20th	Night	32% 5% 20% 30% 12% 1	570
	21st to end	Night	29% 5% 28% 25% 12%	570
October	1st to 10th	Night	24% 6% 30% 29% 10%	654
	11th to 20th	Night	31% 7% 26% 25% 10% 1	821
	21st to end	Night	31% 11% 28% 23% 6%	946
November	1st to 10th	Night	32% 12% 27% 21% 7%	880
	11th to 20th	Night	39% 13% 23% 18% 6%	900
	21st to end	Night	37% 16% 27% 15% 5%	900
December	1st to 10th	Night	32% 16% 28% 18% 6%	900
	11th to 20th	Night	34% 19% 29% 14% 3	900
	21st to end	Night	28% 14% 30% 20% 6% 1	990

Page generated at 2025-01-19 04:06:46. Version ac07

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