Salt Spring Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Salt Spring Island clear sky chart from 2005-11-06 to 2026-10-29.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 37%	154096
	Night	17% 10% 3 7% 5% 4 4 4 5% 6% 35%	146714
Transparency	Day	45% 7% 19% 20% 8% 1	153803
	Night	49% 6% 15% 19% 8% 1	146589
Seeing	Day	18% 6% 17% 29% 24% 6%	18047
	Night	23% 6% 16% 25% 23% 6%	26088

By Month

Percentage Cloud Cover NW (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	29% 16% 5% 11% 6% 5% 4 3 5% 5% 11%	4125
	11th to 20th	Day	17% 12% 5% 9% 5% 4 4 4 5% 7% 30%	4119
	21st to end	Day	29% 14% 4 10% 5% 5% 4 3 4 4 18%	5280
February	1st to 10th	Day	22% 16% 4 10% 6% 6% 4 4 6% 5% 17%	1890
	11th to 20th	Day	21% 15% 4 9% 7% 5% 5% 4 4 6% 22%	1845
	21st to end	Day	18% 14% 5% 10% 7% 7% 6% 5% 5% 6% 18%	1557
March	1st to 10th	Day	18% 13% 5% 11% 6% 6% 6% 4 6% 6% 18%	4838
	11th to 20th	Day	17% 12% 5% 8% 5% 6% 5% 4 5% 6% 26%	5110
	21st to end	Day	20% 13% 4 11% 7% 6% 6% 4 5% 6% 17%	5696
April	1st to 10th	Day	17% 11% 4 9% 6% 6% 6% 5% 8% 7% 21%	2520
	11th to 20th	Day	14% 11% 3 9% 6% 5% 7% 5% 7% 6% 27%	2617
	21st to end	Day	16% 10% 3 7% 6% 5% 6% 3 7% 7% 31%	2756
May	1st to 10th	Day	8% 6% 2 6% 5% 5% 5% 4 6% 7% 46%	8195
	11th to 20th	Day	9% 8% 3 8% 5% 6% 6% 5% 7% 10% 32%	8160
	21st to end	Day	12% 7% 3 8% 4 5% 5% 5% 6% 9% 36%	9209
June	1st to 10th	Day	13% 8% 3 8% 4 5% 6% 4 7% 8% 34%	3150
	11th to 20th	Day	11% 7% 3 9% 6% 6% 6% 6% 7% 9% 31%	3150
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 5% 7% 9% 39%	3150
July	1st to 10th	Day	5% 4 2 5% 4 3 4 3 5% 6% 58%	8820
	11th to 20th	Day	3 3 1 3 3 2 3 3 4 6% 69%	8820
	21st to end	Day	6% 4 2 5% 3 3 4 3 5% 8% 58%	9116
August	1st to 10th	Day	3 3 1 3 2 2 3 3 4 6% 71%	6289
	11th to 20th	Day	5% 5% 2 6% 4 4 4 3 6% 8% 52%	5923
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	6459
September	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 6% 8% 51%	2520
	11th to 20th	Day	12% 7% 3 7% 4 4 4 4 5% 6% 43%	2486
	21st to end	Day	15% 7% 3 7% 5% 4 4 5% 5% 7% 38%	2231
October	1st to 10th	Day	15% 8% 3 9% 5% 4 6% 5% 7% 7% 29%	3380
	11th to 20th	Day	23% 11% 4 8% 4 5% 4 3 4 6% 27%	3361
	21st to end	Day	22% 13% 4 9% 5% 5% 4 3 5% 7% 22%	3388
November	1st to 10th	Day	25% 14% 4 9% 7% 6% 5% 4 5% 5% 16%	1648
	11th to 20th	Day	25% 12% 5% 10% 5% 5% 5% 3 5% 5% 20%	1680
	21st to end	Day	27% 11% 5% 10% 7% 6% 5% 4 4 5% 16%	1680
December	1st to 10th	Day	18% 14% 5% 10% 6% 4 4 3 5% 6% 24%	2638
	11th to 20th	Day	31% 14% 4 9% 6% 6% 5% 4 5% 5% 12%	2715
	21st to end	Day	28% 17% 6% 13% 7% 5% 5% 3 4 4 10%	3575
January	1st to 10th	Night	29% 17% 5% 10% 6% 5% 4 3 4 4 12%	8770
	11th to 20th	Night	18% 11% 3 7% 4 4 4 3 5% 6% 35%	8779
	21st to end	Night	28% 12% 3 8% 4 4 4 3 4 5% 24%	8893
February	1st to 10th	Night	23% 13% 4 10% 5% 5% 5% 3 5% 5% 21%	2730
	11th to 20th	Night	20% 13% 4 8% 5% 4 4 4 4 5% 28%	2662
	21st to end	Night	21% 13% 4 8% 6% 4 4 4 4 6% 26%	2249
March	1st to 10th	Night	16% 11% 4 10% 6% 5% 5% 4 6% 7% 25%	5271
	11th to 20th	Night	14% 11% 4 8% 5% 5% 5% 4 6% 7% 32%	5109
	21st to end	Night	24% 13% 5% 10% 6% 5% 4 3 5% 5% 21%	5521
April	1st to 10th	Night	16% 10% 4 9% 7% 5% 5% 3 6% 8% 27%	2100
	11th to 20th	Night	14% 9% 3 7% 5% 6% 5% 4 5% 8% 34%	1950
	21st to end	Night	14% 9% 3 7% 6% 5% 5% 4 6% 8% 34%	1864
May	1st to 10th	Night	9% 6% 2 6% 3 4 4 3 4 5% 52%	4724
	11th to 20th	Night	9% 7% 3 8% 5% 5% 4 3 7% 8% 41%	4700
	21st to end	Night	11% 7% 3 7% 5% 6% 6% 4 7% 9% 35%	4945
June	1st to 10th	Night	13% 8% 2 7% 6% 5% 4 5% 6% 6% 39%	1470
	11th to 20th	Night	9% 6% 1 7% 4 5% 5% 4 10% 9% 40%	1470
	21st to end	Night	8% 4 2 6% 3 4 5% 5% 7% 10% 46%	1470
July	1st to 10th	Night	5% 3 1 3 3 3 4 3 5% 7% 61%	4140
	11th to 20th	Night	2 2 1 3 2 2 2 2 4 5% 75%	4140
	21st to end	Night	5% 4 2 4 3 3 3 3 5% 7% 61%	4949
August	1st to 10th	Night	2 2 1 2 2 2 2 2 3 5% 78%	3866
	11th to 20th	Night	7% 5% 2 4 3 3 4 3 5% 8% 56%	4142
	21st to end	Night	8% 4 2 5% 3 4 4 4 6% 8% 52%	4693
September	1st to 10th	Night	5% 3 2 4 3 4 4 4 5% 7% 60%	2100
	11th to 20th	Night	11% 6% 2 6% 5% 4 4 4 4 6% 47%	2131
	21st to end	Night	14% 7% 2 7% 4 4 4 4 5% 7% 41%	2389
October	1st to 10th	Night	13% 8% 3 8% 5% 5% 5% 3 5% 6% 40%	4040
	11th to 20th	Night	20% 9% 3 7% 5% 5% 5% 4 5% 6% 31%	4017
	21st to end	Night	22% 11% 4 8% 5% 4 4 3 4 6% 29%	4589
November	1st to 10th	Night	27% 12% 3 9% 6% 5% 5% 4 4 5% 20%	2870
	11th to 20th	Night	25% 12% 3 7% 5% 5% 4 4 5% 5% 24%	2940
	21st to end	Night	24% 11% 4 9% 6% 5% 5% 4 5% 5% 22%	2940
December	1st to 10th	Night	18% 13% 5% 10% 6% 6% 5% 4 5% 6% 22%	4758
	11th to 20th	Night	33% 16% 4 10% 5% 5% 4 3 4 4 12%	5710
	21st to end	Night	26% 14% 4 11% 6% 5% 5% 4 5% 5% 16%	7623

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	74% 8% 8% 9% 2	4125
	11th to 20th	Day	53% 5% 14% 20% 6% 1	4140
	21st to end	Day	71% 5% 9% 10% 4	5281
February	1st to 10th	Day	68% 9% 9% 8% 4 1	1890
	11th to 20th	Day	64% 8% 10% 14% 4 1	1854
	21st to end	Day	63% 10% 13% 10% 3 1	1557
March	1st to 10th	Day	59% 11% 12% 12% 5%	4838
	11th to 20th	Day	55% 8% 12% 19% 5%	5110
	21st to end	Day	64% 9% 17% 8% 2	5696
April	1st to 10th	Day	56% 13% 17% 13% 2	2520
	11th to 20th	Day	51% 10% 15% 13% 9% 2	2617
	21st to end	Day	49% 12% 16% 16% 7% 1	2756
May	1st to 10th	Day	35% 6% 20% 28% 11% 1	8195
	11th to 20th	Day	42% 9% 25% 19% 4	8163
	21st to end	Day	41% 9% 25% 19% 5% 1	9210
June	1st to 10th	Day	44% 10% 21% 17% 6% 2	3150
	11th to 20th	Day	43% 11% 23% 17% 5%	3150
	21st to end	Day	38% 10% 23% 20% 8% 2	3150
July	1st to 10th	Day	26% 5% 23% 25% 17% 5%	8746
	11th to 20th	Day	17% 4 20% 37% 20% 2	8739
	21st to end	Day	25% 4 31% 28% 11% 1	8919
August	1st to 10th	Day	15% 5% 15% 41% 21% 3	6272
	11th to 20th	Day	29% 4 36% 24% 6% 1	5962
	21st to end	Day	37% 7% 27% 21% 7% 1	6458
September	1st to 10th	Day	31% 10% 22% 24% 11% 3	2520
	11th to 20th	Day	40% 9% 18% 20% 12% 1	2486
	21st to end	Day	45% 9% 17% 18% 9% 1	2231
October	1st to 10th	Day	50% 9% 17% 20% 5%	3380
	11th to 20th	Day	58% 7% 12% 16% 6%	3361
	21st to end	Day	61% 7% 14% 14% 5%	3388
November	1st to 10th	Day	68% 8% 12% 8% 4 1	1648
	11th to 20th	Day	65% 7% 11% 11% 4 1	1680
	21st to end	Day	68% 10% 8% 10% 3	1680
December	1st to 10th	Day	62% 6% 11% 16% 5%	2638
	11th to 20th	Day	72% 8% 11% 7% 2	2718
	21st to end	Day	75% 8% 9% 6% 2	3575
January	1st to 10th	Night	74% 6% 8% 9% 3	8770
	11th to 20th	Night	49% 5% 15% 19% 10% 1	8820
	21st to end	Night	64% 5% 10% 17% 4	8893
February	1st to 10th	Night	65% 7% 11% 9% 6% 1	2730
	11th to 20th	Night	57% 7% 12% 16% 7% 1	2664
	21st to end	Night	58% 8% 11% 15% 7% 1	2249
March	1st to 10th	Night	52% 11% 13% 16% 8%	5271
	11th to 20th	Night	50% 9% 13% 23% 5%	5110
	21st to end	Night	64% 8% 13% 12% 3	5521
April	1st to 10th	Night	54% 8% 17% 17% 4	2100
	11th to 20th	Night	47% 8% 14% 19% 9% 2	1950
	21st to end	Night	47% 8% 16% 18% 10% 1	1864
May	1st to 10th	Night	34% 5% 13% 32% 15% 1	4721
	11th to 20th	Night	40% 7% 22% 24% 7%	4700
	21st to end	Night	44% 6% 23% 21% 4	4949
June	1st to 10th	Night	43% 9% 17% 20% 8% 3	1470
	11th to 20th	Night	36% 11% 21% 24% 7%	1470
	21st to end	Night	33% 8% 22% 24% 10% 3	1470
July	1st to 10th	Night	24% 3 23% 28% 15% 7%	4105
	11th to 20th	Night	14% 3 16% 36% 26% 4	4098
	21st to end	Night	25% 3 25% 30% 16% 2	4841
August	1st to 10th	Night	11% 3 16% 39% 26% 4	3858
	11th to 20th	Night	28% 3 33% 27% 6% 2	4169
	21st to end	Night	30% 7% 25% 28% 9% 1	4693
September	1st to 10th	Night	23% 8% 20% 29% 16% 5%	2100
	11th to 20th	Night	38% 6% 15% 20% 16% 4	2131
	21st to end	Night	41% 7% 17% 23% 9% 2	2389
October	1st to 10th	Night	45% 5% 21% 21% 8%	4040
	11th to 20th	Night	53% 5% 14% 22% 6%	4017
	21st to end	Night	55% 7% 14% 17% 7% 1	4589
November	1st to 10th	Night	65% 8% 11% 12% 3 1	2870
	11th to 20th	Night	61% 8% 13% 11% 5% 2	2940
	21st to end	Night	65% 8% 10% 10% 6%	2940
December	1st to 10th	Night	61% 8% 12% 15% 4	4758
	11th to 20th	Night	75% 7% 10% 6% 2	5706
	21st to end	Night	67% 7% 12% 12% 2	7623

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	36% 9% 29% 16% 6% 5%	220
	11th to 20th	Day	33% 14% 17% 20% 16%	220
	21st to end	Day	36% 7% 20% 21% 12% 3	308
February	1st to 10th	Day	29% 11% 24% 22% 13% 1	430
	11th to 20th	Day	31% 8% 24% 25% 10% 2	425
	21st to end	Day	26% 12% 23% 26% 10% 3	355
March	1st to 10th	Day	26% 9% 20% 27% 15% 3	540
	11th to 20th	Day	27% 7% 21% 26% 16% 4	540
	21st to end	Day	26% 7% 23% 25% 14% 4	594
April	1st to 10th	Day	21% 9% 20% 28% 19% 3	540
	11th to 20th	Day	19% 7% 26% 27% 17% 5%	532
	21st to end	Day	21% 5% 18% 33% 19% 5%	540
May	1st to 10th	Day	10% 5% 15% 37% 29% 3	543
	11th to 20th	Day	14% 4 12% 34% 27% 10%	568
	21st to end	Day	14% 4 14% 33% 26% 9%	690
June	1st to 10th	Day	15% 5% 15% 33% 25% 6%	780
	11th to 20th	Day	11% 5% 18% 38% 22% 6%	780
	21st to end	Day	11% 2 12% 32% 34% 8%	780
July	1st to 10th	Day	9% 2 10% 30% 36% 13%	771
	11th to 20th	Day	4 2 11% 34% 37% 12%	768
	21st to end	Day	6% 1 6% 28% 45% 14%	692
August	1st to 10th	Day	5% 2 8% 29% 41% 15%	567
	11th to 20th	Day	6% 2 8% 31% 41% 13%	557
	21st to end	Day	8% 2 14% 33% 35% 8%	627
September	1st to 10th	Day	9% 3 14% 36% 31% 7%	570
	11th to 20th	Day	16% 3 16% 31% 25% 9%	570
	21st to end	Day	19% 5% 21% 29% 22% 3	570
October	1st to 10th	Day	20% 7% 18% 28% 22% 5%	570
	11th to 20th	Day	26% 7% 20% 24% 18% 5%	570
	21st to end	Day	29% 10% 25% 23% 11% 3	488
November	1st to 10th	Day	29% 11% 26% 23% 11%	220
	11th to 20th	Day	32% 7% 20% 20% 17% 4	220
	21st to end	Day	34% 10% 20% 20% 11% 6%	220
December	1st to 10th	Day	35% 8% 17% 18% 20% 4	220
	11th to 20th	Day	36% 9% 23% 20% 12%	220
	21st to end	Day	35% 15% 22% 19% 9%	242
January	1st to 10th	Night	38% 10% 20% 18% 11% 2	950
	11th to 20th	Night	34% 8% 15% 23% 19% 2	950
	21st to end	Night	32% 7% 17% 24% 16% 4	941
February	1st to 10th	Night	31% 9% 20% 24% 13% 3	840
	11th to 20th	Night	25% 8% 20% 27% 18% 2	824
	21st to end	Night	27% 12% 21% 25% 12% 3	692
March	1st to 10th	Night	24% 8% 21% 27% 16% 5%	840
	11th to 20th	Night	27% 8% 21% 23% 17% 4	840
	21st to end	Night	27% 9% 16% 27% 17% 4	924
April	1st to 10th	Night	20% 8% 17% 28% 23% 5%	840
	11th to 20th	Night	17% 7% 21% 29% 20% 5%	702
	21st to end	Night	17% 4 16% 34% 23% 5%	604
May	1st to 10th	Night	12% 2 17% 31% 31% 8%	420
	11th to 20th	Night	14% 3 12% 28% 34% 11%	414
	21st to end	Night	14% 3 9% 33% 35% 7%	455
June	1st to 10th	Night	17% 4 13% 31% 29% 6%	420
	11th to 20th	Night	9% 5% 16% 34% 30% 7%	420
	21st to end	Night	10% 4 10% 32% 37% 7%	420
July	1st to 10th	Night	9% 2 8% 25% 43% 14%	410
	11th to 20th	Night	5% 2 7% 31% 41% 13%	408
	21st to end	Night	5% 1 4 23% 49% 17%	460
August	1st to 10th	Night	6% 2 6% 20% 44% 22%	484
	11th to 20th	Night	6% 2 6% 22% 47% 18%	624
	21st to end	Night	9% 2 9% 28% 39% 12%	742
September	1st to 10th	Night	8% 1 8% 32% 37% 14%	840
	11th to 20th	Night	13% 5% 11% 21% 32% 18%	840
	21st to end	Night	18% 3 16% 26% 29% 8%	840
October	1st to 10th	Night	17% 4 16% 26% 27% 10%	840
	11th to 20th	Night	27% 4 17% 22% 23% 7%	840
	21st to end	Night	29% 6% 19% 26% 15% 4	912
November	1st to 10th	Night	33% 7% 19% 27% 14% 1	820
	11th to 20th	Night	31% 9% 20% 24% 13% 3	840
	21st to end	Night	30% 9% 19% 23% 14% 4	840
December	1st to 10th	Night	27% 10% 18% 26% 17% 3	857
	11th to 20th	Night	38% 11% 22% 19% 9% 1	950
	21st to end	Night	36% 12% 22% 20% 8% 1	1045

Page generated at 2026-10-26 01:37:50. Version ac07

Copyright © 2026 Attilla Danko.