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 2024-01-27.

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	27% 11% 4 7% 6% 3 4 4 4 6% 24%	74662
	Night	26% 11% 4 7% 6% 3 4 4 4 6% 24%	75368
Transparency	Day	61% 7% 12% 14% 6% 1	74365
	Night	62% 6% 12% 14% 6%	75200
Seeing	Day	33% 9% 23% 23% 10% 2	16777
	Night	32% 10% 25% 23% 9% 1	23953

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	20% 14% 9% 13% 9% 4 5% 4 4 4 14%	1516
	11th to 20th	Day	21% 15% 6% 12% 6% 4 6% 4 4 6% 16%	1520
	21st to end	Day	16% 15% 7% 12% 9% 5% 6% 6% 5% 4 14%	1633
February	1st to 10th	Day	21% 12% 6% 12% 11% 4 6% 6% 5% 5% 13%	1470
	11th to 20th	Day	22% 14% 5% 10% 8% 5% 5% 5% 5% 6% 17%	1669
	21st to end	Day	13% 12% 6% 10% 11% 5% 5% 5% 4 5% 25%	1480
March	1st to 10th	Day	16% 12% 7% 11% 8% 3 4 5% 4 5% 24%	1796
	11th to 20th	Day	21% 13% 4 9% 8% 4 6% 4 3 6% 22%	1840
	21st to end	Day	20% 14% 5% 7% 7% 2 4 4 5% 6% 26%	2376
April	1st to 10th	Day	26% 14% 6% 10% 6% 3 4 4 4 5% 19%	2160
	11th to 20th	Day	23% 11% 4 6% 5% 3 3 4 4 7% 31%	2179
	21st to end	Day	30% 11% 4 5% 4 2 3 4 3 4 30%	2340
May	1st to 10th	Day	28% 10% 3 6% 4 2 3 4 5% 6% 27%	2494
	11th to 20th	Day	27% 10% 4 6% 4 2 4 5% 4 6% 29%	2478
	21st to end	Day	26% 10% 3 5% 5% 4 6% 4 6% 8% 24%	2724
June	1st to 10th	Day	37% 10% 4 6% 4 2 3 4 4 6% 21%	2654
	11th to 20th	Day	27% 8% 3 5% 5% 3 5% 4 5% 7% 28%	2700
	21st to end	Day	44% 10% 3 6% 4 2 3 3 3 5% 16%	2671
July	1st to 10th	Day	32% 10% 3 6% 5% 3 5% 4 4 6% 24%	2520
	11th to 20th	Day	36% 9% 2 5% 4 3 3 4 5% 5% 25%	2520
	21st to end	Day	39% 8% 3 4 4 3 4 4 3 5% 22%	2745
August	1st to 10th	Day	27% 8% 2 6% 6% 3 4 5% 4 8% 26%	2506
	11th to 20th	Day	29% 7% 3 6% 5% 3 5% 4 4 6% 28%	2374
	21st to end	Day	26% 6% 3 5% 5% 3 5% 6% 5% 7% 29%	2412
September	1st to 10th	Day	28% 6% 2 4 5% 3 5% 4 5% 7% 31%	2160
	11th to 20th	Day	28% 7% 3 5% 4 3 4 4 4 7% 30%	2053
	21st to end	Day	26% 8% 2 5% 4 2 4 4 4 6% 34%	1980
October	1st to 10th	Day	23% 7% 3 5% 4 3 5% 5% 5% 7% 34%	1900
	11th to 20th	Day	29% 8% 3 5% 5% 3 3 4 4 7% 29%	1691
	21st to end	Day	27% 10% 4 6% 5% 3 4 5% 6% 7% 24%	1782
November	1st to 10th	Day	30% 12% 4 8% 5% 3 4 4 4 5% 20%	1670
	11th to 20th	Day	27% 14% 4 8% 6% 2 4 4 4 6% 21%	1610
	21st to end	Day	24% 14% 5% 8% 5% 3 4 4 5% 7% 20%	1430
December	1st to 10th	Day	28% 15% 4 8% 6% 4 5% 4 5% 5% 15%	1330
	11th to 20th	Day	32% 13% 4 8% 5% 3 4 5% 5% 5% 16%	1668
	21st to end	Day	23% 15% 5% 7% 5% 4 5% 5% 5% 6% 21%	2611
January	1st to 10th	Night	22% 14% 7% 8% 8% 4 4 5% 5% 5% 17%	2649
	11th to 20th	Night	22% 17% 7% 11% 6% 3 4 5% 6% 5% 14%	2660
	21st to end	Night	19% 12% 7% 10% 9% 4 6% 5% 4 6% 18%	2867
February	1st to 10th	Night	22% 13% 5% 11% 9% 4 5% 4 5% 6% 17%	2488
	11th to 20th	Night	20% 15% 5% 10% 8% 4 5% 5% 5% 6% 17%	2176
	21st to end	Night	13% 12% 5% 11% 8% 4 5% 5% 5% 6% 27%	1776
March	1st to 10th	Night	18% 11% 6% 10% 7% 4 5% 4 4 5% 26%	2151
	11th to 20th	Night	19% 12% 5% 8% 7% 3 4 5% 5% 6% 27%	2115
	21st to end	Night	22% 13% 5% 8% 5% 3 4 4 4 5% 26%	1980
April	1st to 10th	Night	29% 13% 5% 6% 4 3 3 4 4 6% 24%	1800
	11th to 20th	Night	21% 10% 3 6% 6% 4 5% 5% 4 5% 30%	1730
	21st to end	Night	27% 11% 4 6% 4 2 4 3 4 5% 29%	1620
May	1st to 10th	Night	27% 11% 3 5% 6% 3 3 4 3 5% 29%	1463
	11th to 20th	Night	30% 10% 3 5% 4 2 3 3 4 5% 31%	1416
	21st to end	Night	30% 9% 4 5% 6% 2 3 4 4 6% 27%	1550
June	1st to 10th	Night	38% 12% 4 5% 5% 2 3 2 3 5% 21%	1301
	11th to 20th	Night	27% 9% 3 6% 5% 2 4 4 4 6% 28%	1260
	21st to end	Night	41% 13% 3 5% 4 2 3 3 3 5% 19%	1283
July	1st to 10th	Night	37% 10% 4 5% 5% 3 3 4 4 4 21%	1440
	11th to 20th	Night	39% 11% 3 5% 3 2 3 3 3 4 25%	1440
	21st to end	Night	38% 10% 3 5% 4 2 4 4 4 6% 21%	1573
August	1st to 10th	Night	29% 10% 2 5% 5% 3 4 4 5% 6% 26%	1433
	11th to 20th	Night	30% 10% 3 5% 5% 2 4 3 5% 5% 27%	1525
	21st to end	Night	25% 10% 2 6% 4 2 4 4 4 6% 33%	1942
September	1st to 10th	Night	28% 6% 2 5% 5% 3 3 4 4 6% 34%	1800
	11th to 20th	Night	31% 7% 2 5% 3 2 4 4 4 5% 35%	1906
	21st to end	Night	27% 6% 3 4 4 2 3 3 5% 6% 37%	1980
October	1st to 10th	Night	22% 6% 2 5% 5% 3 5% 5% 4 6% 37%	2059
	11th to 20th	Night	29% 8% 3 5% 4 3 4 4 4 4 32%	2268
	21st to end	Night	27% 10% 3 6% 5% 3 4 5% 5% 6% 26%	2574
November	1st to 10th	Night	29% 10% 3 6% 6% 3 4 4 6% 6% 23%	2408
	11th to 20th	Night	30% 13% 3 7% 5% 3 5% 4 4 6% 20%	2569
	21st to end	Night	26% 15% 4 7% 5% 3 5% 4 5% 5% 21%	2746
December	1st to 10th	Night	27% 15% 5% 8% 6% 4 4 4 4 5% 18%	2850
	11th to 20th	Night	34% 10% 5% 8% 7% 3 4 4 4 5% 16%	3531
	21st to end	Night	24% 14% 6% 8% 7% 3 5% 5% 4 6% 19%	5039

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	76% 5% 8% 9% 3	1517
	11th to 20th	Day	70% 6% 12% 9% 2	1520
	21st to end	Day	72% 7% 11% 7% 3	1633
February	1st to 10th	Day	73% 6% 11% 7% 2	1470
	11th to 20th	Day	69% 6% 12% 10% 3 1	1677
	21st to end	Day	61% 6% 12% 14% 6% 1	1480
March	1st to 10th	Day	62% 6% 12% 14% 7% 1	1800
	11th to 20th	Day	63% 5% 9% 14% 8%	1840
	21st to end	Day	58% 7% 11% 14% 8% 2	2376
April	1st to 10th	Day	66% 6% 9% 10% 6% 2	2160
	11th to 20th	Day	54% 6% 9% 18% 11% 1	2179
	21st to end	Day	58% 6% 11% 16% 8% 1	2340
May	1st to 10th	Day	56% 7% 12% 17% 7% 1	2494
	11th to 20th	Day	55% 6% 12% 16% 9% 1	2482
	21st to end	Day	57% 7% 12% 17% 6% 1	2724
June	1st to 10th	Day	66% 5% 9% 14% 6%	2654
	11th to 20th	Day	55% 8% 14% 17% 5%	2700
	21st to end	Day	72% 6% 9% 8% 4 1	2671
July	1st to 10th	Day	62% 6% 13% 16% 4	2450
	11th to 20th	Day	63% 5% 10% 15% 7%	2444
	21st to end	Day	65% 8% 10% 14% 4	2592
August	1st to 10th	Day	55% 9% 18% 13% 4	2492
	11th to 20th	Day	55% 9% 14% 15% 6%	2374
	21st to end	Day	51% 7% 19% 19% 4	2412
September	1st to 10th	Day	50% 7% 14% 18% 9% 1	2160
	11th to 20th	Day	52% 7% 14% 19% 7% 1	2053
	21st to end	Day	50% 7% 16% 19% 9%	1980
October	1st to 10th	Day	47% 9% 14% 20% 9% 1	1900
	11th to 20th	Day	55% 6% 15% 18% 6%	1691
	21st to end	Day	58% 8% 12% 18% 4	1782
November	1st to 10th	Day	64% 7% 13% 13% 4	1670
	11th to 20th	Day	64% 7% 12% 11% 5%	1610
	21st to end	Day	65% 7% 15% 9% 4	1430
December	1st to 10th	Day	70% 8% 10% 8% 3	1330
	11th to 20th	Day	72% 7% 10% 8% 3	1667
	21st to end	Day	63% 9% 16% 11% 2	2611
January	1st to 10th	Night	72% 7% 10% 8% 3	2649
	11th to 20th	Night	74% 6% 10% 7% 3	2660
	21st to end	Night	69% 5% 13% 10% 3	2867
February	1st to 10th	Night	72% 5% 11% 8% 3	2488
	11th to 20th	Night	70% 6% 12% 9% 2	2179
	21st to end	Night	59% 5% 14% 16% 5% 1	1776
March	1st to 10th	Night	62% 5% 13% 13% 7%	2160
	11th to 20th	Night	58% 6% 11% 17% 7% 1	2116
	21st to end	Night	61% 5% 10% 15% 9% 1	1980
April	1st to 10th	Night	62% 6% 10% 14% 8% 1	1800
	11th to 20th	Night	55% 6% 11% 15% 11% 2	1730
	21st to end	Night	59% 5% 10% 16% 9% 1	1620
May	1st to 10th	Night	59% 5% 11% 17% 8%	1463
	11th to 20th	Night	56% 5% 8% 20% 9% 1	1417
	21st to end	Night	60% 5% 10% 17% 7%	1551
June	1st to 10th	Night	69% 4 7% 14% 6%	1301
	11th to 20th	Night	59% 5% 10% 20% 6%	1260
	21st to end	Night	70% 5% 7% 10% 7%	1283
July	1st to 10th	Night	67% 5% 11% 11% 6%	1401
	11th to 20th	Night	64% 4 9% 14% 8%	1392
	21st to end	Night	64% 7% 10% 13% 5%	1486
August	1st to 10th	Night	56% 10% 12% 17% 5%	1422
	11th to 20th	Night	58% 6% 12% 15% 7% 1	1525
	21st to end	Night	53% 7% 13% 22% 5%	1942
September	1st to 10th	Night	50% 6% 14% 20% 9% 1	1800
	11th to 20th	Night	52% 6% 12% 19% 10% 1	1906
	21st to end	Night	48% 6% 15% 20% 10% 1	1980
October	1st to 10th	Night	46% 9% 15% 20% 10% 1	2059
	11th to 20th	Night	55% 5% 15% 19% 6%	2268
	21st to end	Night	59% 7% 13% 16% 5% 1	2574
November	1st to 10th	Night	60% 8% 15% 13% 3	2408
	11th to 20th	Night	66% 7% 12% 11% 5%	2569
	21st to end	Night	66% 7% 14% 9% 4	2746
December	1st to 10th	Night	69% 8% 11% 10% 3	2850
	11th to 20th	Night	72% 7% 10% 9% 2	3533
	21st to end	Night	65% 9% 13% 11% 2	5039

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	26% 17% 35% 17% 4	370
	11th to 20th	Day	31% 15% 31% 18% 5% 1	370
	21st to end	Day	23% 15% 33% 22% 6%	393
February	1st to 10th	Day	30% 19% 32% 16% 3	340
	11th to 20th	Day	30% 18% 33% 16% 2	336
	21st to end	Day	19% 16% 29% 24% 10% 2	280
March	1st to 10th	Day	22% 20% 34% 19% 5% 1	340
	11th to 20th	Day	29% 13% 25% 21% 9% 3	342
	21st to end	Day	30% 14% 24% 21% 7% 4	462
April	1st to 10th	Day	34% 17% 26% 17% 5%	420
	11th to 20th	Day	29% 10% 24% 25% 10% 2	457
	21st to end	Day	34% 7% 24% 25% 9% 2	600
May	1st to 10th	Day	38% 4 22% 26% 8% 2	603
	11th to 20th	Day	26% 5% 25% 26% 15% 3	624
	21st to end	Day	32% 8% 23% 24% 12% 1	680
June	1st to 10th	Day	43% 4 15% 26% 11% 2	630
	11th to 20th	Day	31% 4 17% 31% 14% 2	630
	21st to end	Day	50% 4 11% 22% 10% 3	630
July	1st to 10th	Day	39% 5% 16% 26% 13% 2	620
	11th to 20th	Day	41% 4 12% 29% 12% 1	618
	21st to end	Day	43% 6% 13% 24% 13% 2	685
August	1st to 10th	Day	30% 3 15% 32% 19% 1	625
	11th to 20th	Day	33% 2 17% 27% 18% 2	617
	21st to end	Day	29% 5% 18% 29% 16% 3	531
September	1st to 10th	Day	28% 5% 22% 31% 12% 3	450
	11th to 20th	Day	32% 8% 22% 25% 10% 3	396
	21st to end	Day	33% 6% 25% 26% 8% 3	360
October	1st to 10th	Day	21% 8% 32% 25% 12% 1	360
	11th to 20th	Day	35% 8% 24% 16% 14% 3	360
	21st to end	Day	31% 11% 27% 23% 8% 1	396
November	1st to 10th	Day	33% 17% 24% 20% 5% 1	365
	11th to 20th	Day	32% 14% 25% 19% 7% 2	370
	21st to end	Day	36% 17% 26% 16% 5%	370
December	1st to 10th	Day	33% 14% 30% 15% 7% 1	370
	11th to 20th	Day	35% 20% 26% 15% 4 1	370
	21st to end	Day	29% 18% 28% 17% 7% 2	407
January	1st to 10th	Night	29% 17% 31% 18% 4	850
	11th to 20th	Night	30% 19% 28% 18% 3 1	850
	21st to end	Night	24% 13% 34% 24% 4	914
February	1st to 10th	Night	29% 17% 32% 18% 4	786
	11th to 20th	Night	29% 15% 37% 16% 4	703
	21st to end	Night	18% 14% 32% 27% 7% 2	592
March	1st to 10th	Night	23% 15% 37% 20% 5%	720
	11th to 20th	Night	26% 11% 30% 24% 8% 1	684
	21st to end	Night	27% 10% 32% 22% 7% 1	594
April	1st to 10th	Night	35% 11% 26% 21% 6% 1	540
	11th to 20th	Night	27% 9% 24% 31% 8% 1	534
	21st to end	Night	33% 6% 24% 28% 8% 1	540
May	1st to 10th	Night	31% 5% 21% 29% 12% 2	540
	11th to 20th	Night	33% 3 20% 30% 11% 2	532
	21st to end	Night	34% 4 23% 26% 11% 1	583
June	1st to 10th	Night	43% 5% 17% 26% 9% 1	540
	11th to 20th	Night	30% 5% 14% 31% 18% 2	540
	21st to end	Night	45% 3 13% 24% 13% 1	540
July	1st to 10th	Night	43% 2 12% 29% 13% 1	526
	11th to 20th	Night	44% 2 13% 27% 13% 1	522
	21st to end	Night	42% 3 11% 26% 17% 1	590
August	1st to 10th	Night	35% 3 11% 27% 22% 2	538
	11th to 20th	Night	33% 3 13% 30% 20% 1	532
	21st to end	Night	29% 4 17% 28% 20% 2	594
September	1st to 10th	Night	29% 7% 21% 28% 12% 2	540
	11th to 20th	Night	34% 6% 20% 30% 10% 1	540
	21st to end	Night	30% 5% 28% 24% 12%	540
October	1st to 10th	Night	25% 7% 30% 29% 9%	619
	11th to 20th	Night	32% 7% 25% 26% 10% 1	774
	21st to end	Night	31% 12% 28% 22% 7%	891
November	1st to 10th	Night	33% 12% 26% 21% 7%	830
	11th to 20th	Night	37% 14% 24% 19% 7%	850
	21st to end	Night	35% 17% 28% 15% 4	850
December	1st to 10th	Night	33% 16% 27% 18% 6%	850
	11th to 20th	Night	34% 19% 30% 14% 3	850
	21st to end	Night	28% 15% 31% 19% 6% 1	935

Page generated at 2024-01-24 10:37:32. Version ac07

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