Cypress Hills Dark-Sky Preserve - SSSP
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cypress Hills Dark-Sky Preserve - SSSP clear sky chart from 2005-11-06 to 2025-09-04.

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	7% 7% 3 8% 5% 5% 5% 4 6% 8% 41%	135433
	Night	6% 7% 3 8% 6% 5% 6% 5% 6% 8% 40%	130579
Transparency	Day	38% 7% 15% 25% 12% 2	130047
	Night	39% 7% 16% 24% 12% 2	126975
Seeing	Day	12% 12% 32% 28% 14% 3	16773
	Night	10% 11% 35% 31% 11% 1	25965

By Month

Percentage Cloud Cover SW (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	4 13% 6% 12% 8% 7% 6% 5% 7% 8% 24%	3179
	11th to 20th	Day	1 4 3 12% 6% 7% 10% 7% 10% 9% 31%	3180
	21st to end	Day	2 6% 3 8% 7% 6% 6% 5% 5% 8% 44%	3889
February	1st to 10th	Day	5% 11% 4 11% 8% 7% 7% 5% 7% 8% 26%	1800
	11th to 20th	Day	4 9% 6% 11% 7% 8% 6% 5% 8% 10% 27%	1755
	21st to end	Day	4 10% 5% 12% 9% 6% 6% 6% 7% 8% 27%	1485
March	1st to 10th	Day	3 7% 3 10% 6% 7% 6% 5% 7% 11% 35%	4721
	11th to 20th	Day	4 7% 3 8% 6% 5% 6% 6% 8% 11% 36%	5000
	21st to end	Day	6% 15% 6% 15% 9% 6% 6% 4 6% 7% 20%	5502
April	1st to 10th	Day	6% 10% 3 8% 7% 7% 6% 5% 7% 8% 34%	2400
	11th to 20th	Day	9% 14% 4 10% 6% 5% 6% 4 6% 6% 29%	2557
	21st to end	Day	10% 11% 4 9% 5% 4 5% 4 7% 8% 33%	2600
May	1st to 10th	Day	12% 11% 4 7% 4 4 4 4 5% 6% 39%	6340
	11th to 20th	Day	11% 10% 3 11% 6% 7% 6% 5% 6% 8% 27%	6298
	21st to end	Day	11% 8% 3 8% 5% 5% 5% 5% 6% 7% 37%	7352
June	1st to 10th	Day	13% 9% 3 6% 6% 5% 5% 5% 7% 7% 35%	3000
	11th to 20th	Day	16% 8% 3 6% 5% 5% 5% 5% 6% 8% 33%	3000
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 6% 9% 44%	3000
July	1st to 10th	Day	6% 3 2 5% 4 5% 5% 4 6% 8% 52%	6779
	11th to 20th	Day	5% 4 2 6% 4 5% 6% 5% 7% 8% 50%	6780
	21st to end	Day	6% 3 1 4 3 4 4 4 5% 7% 58%	7283
August	1st to 10th	Day	7% 6% 3 6% 4 5% 5% 5% 7% 8% 44%	6016
	11th to 20th	Day	3 3 1 4 3 4 5% 4 8% 10% 54%	5798
	21st to end	Day	8% 4 1 4 2 3 3 2 4 6% 63%	6465
September	1st to 10th	Day	10% 5% 2 5% 4 3 4 3 4 7% 52%	2322
	11th to 20th	Day	12% 6% 2 6% 4 3 4 4 5% 8% 45%	2200
	21st to end	Day	10% 6% 1 4 3 3 3 3 6% 7% 52%	2052
October	1st to 10th	Day	5% 5% 2 6% 3 4 4 4 6% 8% 52%	3170
	11th to 20th	Day	4 5% 2 6% 4 4 4 4 7% 10% 52%	3150
	21st to end	Day	5% 7% 3 8% 4 5% 6% 3 5% 7% 48%	3093
November	1st to 10th	Day	10% 12% 6% 8% 7% 5% 4 3 6% 7% 32%	1568
	11th to 20th	Day	4 8% 3 10% 7% 7% 5% 5% 5% 8% 39%	1600
	21st to end	Day	6% 10% 4 9% 7% 6% 7% 6% 8% 7% 32%	1600
December	1st to 10th	Day	3 7% 4 12% 9% 10% 9% 6% 6% 7% 27%	2356
	11th to 20th	Day	7% 9% 4 12% 8% 7% 6% 5% 6% 7% 28%	2645
	21st to end	Day	3 7% 3 8% 7% 6% 6% 5% 6% 7% 41%	3498
January	1st to 10th	Night	2 11% 5% 11% 7% 7% 8% 5% 8% 10% 28%	6766
	11th to 20th	Night	2 6% 4 10% 8% 8% 10% 7% 8% 10% 29%	6780
	21st to end	Night	2 5% 3 8% 7% 7% 9% 6% 7% 9% 39%	7104
February	1st to 10th	Night	5% 11% 4 10% 6% 7% 7% 5% 8% 9% 28%	2600
	11th to 20th	Night	3 9% 4 10% 8% 7% 8% 5% 9% 9% 28%	2532
	21st to end	Night	4 10% 4 10% 8% 7% 6% 5% 7% 8% 32%	2145
March	1st to 10th	Night	3 7% 3 9% 7% 7% 9% 5% 7% 9% 34%	5163
	11th to 20th	Night	5% 7% 2 7% 4 5% 6% 5% 7% 10% 41%	5000
	21st to end	Night	7% 14% 6% 14% 10% 8% 6% 4 5% 7% 19%	5458
April	1st to 10th	Night	7% 9% 4 9% 7% 7% 4 4 6% 8% 35%	2000
	11th to 20th	Night	9% 11% 4 10% 5% 5% 6% 4 6% 8% 32%	1788
	21st to end	Night	9% 9% 4 9% 5% 5% 5% 4 6% 7% 37%	1799
May	1st to 10th	Night	14% 9% 3 6% 4 3 4 3 5% 6% 45%	3640
	11th to 20th	Night	13% 8% 3 9% 6% 6% 6% 5% 7% 8% 29%	3617
	21st to end	Night	10% 6% 3 7% 5% 5% 5% 3 6% 8% 43%	3520
June	1st to 10th	Night	13% 7% 2 7% 3 4 4 4 6% 7% 42%	1400
	11th to 20th	Night	11% 6% 1 7% 6% 5% 5% 4 5% 8% 42%	1400
	21st to end	Night	7% 3 1 5% 4 3 4 5% 7% 9% 53%	1400
July	1st to 10th	Night	5% 3 1 4 3 3 3 3 6% 8% 60%	3180
	11th to 20th	Night	6% 4 2 5% 3 3 5% 4 6% 7% 55%	3180
	21st to end	Night	5% 2 1 3 3 4 4 4 6% 8% 60%	3558
August	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 5% 8% 49%	3794
	11th to 20th	Night	4 2 2 5% 4 5% 5% 4 7% 10% 52%	4051
	21st to end	Night	10% 5% 2 4 2 3 3 2 3 5% 62%	4509
September	1st to 10th	Night	10% 4 2 5% 3 3 4 3 5% 7% 56%	1925
	11th to 20th	Night	9% 7% 3 6% 3 5% 4 4 6% 7% 46%	1976
	21st to end	Night	7% 6% 2 5% 4 3 3 4 6% 8% 51%	2128
October	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 8% 51%	3800
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 4 5% 9% 50%	3778
	21st to end	Night	5% 7% 3 7% 5% 4 5% 4 5% 7% 49%	4431
November	1st to 10th	Night	9% 10% 5% 9% 5% 5% 5% 5% 5% 8% 34%	2730
	11th to 20th	Night	4 8% 3 9% 8% 7% 6% 5% 7% 9% 36%	2800
	21st to end	Night	4 11% 4 9% 6% 5% 6% 5% 7% 8% 35%	2800
December	1st to 10th	Night	2 8% 3 11% 9% 8% 9% 5% 8% 8% 29%	4823
	11th to 20th	Night	3 10% 5% 11% 9% 7% 6% 7% 9% 7% 26%	5546
	21st to end	Night	3 7% 3 7% 4 5% 5% 5% 7% 7% 46%	7458

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	52% 9% 17% 18% 3 1	3179
	11th to 20th	Day	46% 7% 13% 20% 12% 2	3180
	21st to end	Day	38% 8% 22% 26% 6%	3889
February	1st to 10th	Day	52% 10% 14% 16% 8%	1800
	11th to 20th	Day	47% 11% 16% 17% 8% 2	1764
	21st to end	Day	50% 9% 15% 16% 9% 1	1485
March	1st to 10th	Day	38% 9% 20% 22% 10% 1	4721
	11th to 20th	Day	39% 8% 18% 24% 10%	5000
	21st to end	Day	56% 13% 16% 11% 4	5502
April	1st to 10th	Day	44% 9% 17% 21% 8%	2400
	11th to 20th	Day	51% 8% 14% 20% 7% 1	2560
	21st to end	Day	45% 9% 15% 24% 7% 1	2600
May	1st to 10th	Day	42% 7% 12% 25% 10% 3	6340
	11th to 20th	Day	47% 10% 14% 22% 6%	6302
	21st to end	Day	39% 10% 14% 26% 11%	7353
June	1st to 10th	Day	44% 8% 17% 21% 9% 1	3000
	11th to 20th	Day	47% 7% 14% 21% 10% 1	3000
	21st to end	Day	32% 8% 18% 29% 11% 1	3000
July	1st to 10th	Day	29% 4 18% 23% 20% 6%	6706
	11th to 20th	Day	30% 4 17% 29% 16% 4	6699
	21st to end	Day	25% 3 13% 30% 21% 8%	7072
August	1st to 10th	Day	30% 6% 11% 32% 19% 2	4382
	11th to 20th	Day	24% 5% 17% 39% 14% 1	4197
	21st to end	Day	23% 4 12% 40% 19% 2	4663
September	1st to 10th	Day	32% 6% 14% 23% 18% 7%	2322
	11th to 20th	Day	36% 6% 16% 26% 13% 3	2200
	21st to end	Day	29% 7% 14% 31% 17% 2	2052
October	1st to 10th	Day	28% 5% 13% 36% 14% 3	3170
	11th to 20th	Day	27% 4 18% 36% 12% 2	3150
	21st to end	Day	36% 5% 11% 37% 12%	3093
November	1st to 10th	Day	50% 8% 14% 18% 8% 1	1568
	11th to 20th	Day	40% 9% 20% 22% 8% 1	1600
	21st to end	Day	46% 11% 17% 18% 7% 1	1600
December	1st to 10th	Day	54% 5% 20% 16% 4 1	2356
	11th to 20th	Day	52% 6% 20% 19% 3	2644
	21st to end	Day	41% 6% 10% 24% 13% 5%	3498
January	1st to 10th	Night	46% 9% 19% 18% 6% 1	6766
	11th to 20th	Night	48% 7% 16% 13% 12% 4	6780
	21st to end	Night	40% 8% 20% 26% 6% 1	7104
February	1st to 10th	Night	49% 7% 15% 16% 11% 2	2600
	11th to 20th	Night	46% 9% 15% 16% 11% 2	2533
	21st to end	Night	46% 7% 13% 23% 9% 2	2145
March	1st to 10th	Night	40% 9% 21% 15% 14% 1	5163
	11th to 20th	Night	35% 6% 19% 27% 12% 1	5000
	21st to end	Night	56% 12% 15% 11% 5% 1	5458
April	1st to 10th	Night	44% 9% 15% 23% 9% 1	2000
	11th to 20th	Night	46% 8% 13% 21% 11% 2	1788
	21st to end	Night	43% 9% 13% 25% 9% 1	1799
May	1st to 10th	Night	37% 8% 9% 29% 16% 2	3640
	11th to 20th	Night	44% 9% 17% 20% 8%	3618
	21st to end	Night	33% 10% 19% 29% 9% 1	3520
June	1st to 10th	Night	38% 8% 18% 25% 10% 1	1400
	11th to 20th	Night	38% 8% 13% 24% 15% 2	1400
	21st to end	Night	26% 7% 18% 34% 13% 2	1400
July	1st to 10th	Night	24% 3 15% 31% 23% 4	3145
	11th to 20th	Night	28% 3 13% 31% 19% 5%	3138
	21st to end	Night	22% 3 13% 32% 22% 8%	3457
August	1st to 10th	Night	27% 5% 10% 34% 21% 3	2752
	11th to 20th	Night	28% 4 16% 35% 14% 3	2928
	21st to end	Night	29% 4 11% 33% 20% 3	3245
September	1st to 10th	Night	29% 5% 13% 27% 18% 9%	1925
	11th to 20th	Night	35% 7% 13% 25% 15% 5%	1976
	21st to end	Night	29% 4 16% 29% 19% 2	2128
October	1st to 10th	Night	31% 5% 12% 35% 16% 1	3800
	11th to 20th	Night	30% 5% 15% 32% 16% 2	3778
	21st to end	Night	34% 5% 11% 37% 13%	4431
November	1st to 10th	Night	46% 8% 14% 21% 10% 1	2730
	11th to 20th	Night	42% 9% 20% 19% 10%	2800
	21st to end	Night	43% 9% 22% 18% 7% 1	2800
December	1st to 10th	Night	50% 8% 20% 15% 6% 1	4823
	11th to 20th	Night	51% 7% 23% 16% 3	5547
	21st to end	Night	35% 5% 12% 26% 16% 5%	7458

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	13% 14% 32% 27% 10% 5%	200
	11th to 20th	Day	7% 14% 41% 23% 14% 3	200
	21st to end	Day	9% 18% 36% 27% 9% 1	255
February	1st to 10th	Day	13% 19% 42% 19% 7% 1	300
	11th to 20th	Day	10% 12% 40% 27% 9% 2	300
	21st to end	Day	9% 10% 39% 30% 10% 2	249
March	1st to 10th	Day	10% 15% 35% 28% 10% 1	435
	11th to 20th	Day	6% 17% 38% 25% 9% 4	500
	21st to end	Day	11% 13% 38% 24% 12% 2	550
April	1st to 10th	Day	9% 19% 38% 25% 8%	500
	11th to 20th	Day	13% 19% 35% 24% 7% 1	492
	21st to end	Day	16% 12% 31% 30% 9% 1	500
May	1st to 10th	Day	15% 9% 25% 31% 16% 4	703
	11th to 20th	Day	14% 9% 28% 29% 16% 4	725
	21st to end	Day	19% 10% 26% 23% 18% 5%	789
June	1st to 10th	Day	14% 13% 27% 28% 16% 2	730
	11th to 20th	Day	18% 16% 34% 20% 11% 1	730
	21st to end	Day	13% 10% 26% 27% 20% 4	730
July	1st to 10th	Day	7% 4 24% 42% 19% 2	721
	11th to 20th	Day	9% 7% 30% 35% 16% 2	718
	21st to end	Day	6% 6% 27% 35% 21% 5%	794
August	1st to 10th	Day	8% 7% 26% 36% 18% 5%	637
	11th to 20th	Day	8% 6% 27% 37% 19% 4	517
	21st to end	Day	8% 8% 29% 31% 20% 4	583
September	1st to 10th	Day	12% 10% 30% 32% 15% 1	503
	11th to 20th	Day	14% 10% 30% 30% 14% 2	490
	21st to end	Day	15% 11% 33% 26% 11% 3	452
October	1st to 10th	Day	16% 12% 28% 24% 16% 4	300
	11th to 20th	Day	9% 16% 36% 25% 12% 2	300
	21st to end	Day	12% 19% 39% 23% 7% 1	330
November	1st to 10th	Day	15% 21% 34% 22% 7%	300
	11th to 20th	Day	10% 28% 36% 19% 7% 1	300
	21st to end	Day	11% 15% 43% 19% 9% 4	300
December	1st to 10th	Day	12% 13% 40% 27% 6% 2	220
	11th to 20th	Day	9% 25% 41% 22% 4	200
	21st to end	Day	10% 12% 31% 35% 9% 2	220
January	1st to 10th	Night	9% 17% 40% 26% 8% 1	1000
	11th to 20th	Night	8% 18% 40% 25% 8% 1	1000
	21st to end	Night	9% 18% 38% 26% 8% 1	1018
February	1st to 10th	Night	10% 15% 33% 30% 10% 2	800
	11th to 20th	Night	6% 16% 44% 25% 8% 1	784
	21st to end	Night	8% 10% 36% 30% 13% 3	660
March	1st to 10th	Night	8% 13% 38% 31% 9% 1	800
	11th to 20th	Night	10% 10% 40% 29% 10% 2	800
	21st to end	Night	11% 11% 36% 30% 11% 1	874
April	1st to 10th	Night	9% 10% 40% 30% 10% 1	600
	11th to 20th	Night	14% 11% 36% 30% 9% 1	593
	21st to end	Night	14% 10% 29% 36% 11%	600
May	1st to 10th	Night	15% 7% 26% 34% 17% 1	600
	11th to 20th	Night	13% 6% 28% 35% 16% 2	591
	21st to end	Night	17% 10% 24% 31% 16% 2	458
June	1st to 10th	Night	15% 10% 26% 30% 18% 2	400
	11th to 20th	Night	15% 10% 31% 34% 10%	400
	21st to end	Night	9% 6% 25% 43% 16% 2	400
July	1st to 10th	Night	7% 4 25% 46% 16% 1	390
	11th to 20th	Night	7% 5% 29% 45% 14% 1	388
	21st to end	Night	5% 3 24% 45% 22% 1	478
August	1st to 10th	Night	9% 4 22% 43% 20% 2	597
	11th to 20th	Night	8% 4 21% 45% 22% 1	594
	21st to end	Night	11% 5% 25% 39% 19% 1	660
September	1st to 10th	Night	11% 3 30% 39% 15% 2	579
	11th to 20th	Night	13% 7% 27% 36% 15% 2	646
	21st to end	Night	9% 7% 36% 33% 12% 3	760
October	1st to 10th	Night	14% 10% 29% 32% 15% 1	760
	11th to 20th	Night	10% 11% 36% 31% 10% 1	760
	21st to end	Night	11% 16% 38% 28% 7%	900
November	1st to 10th	Night	16% 13% 39% 26% 5%	975
	11th to 20th	Night	10% 18% 44% 21% 6% 1	1000
	21st to end	Night	9% 14% 42% 29% 6%	1000
December	1st to 10th	Night	9% 15% 39% 26% 10% 2	1000
	11th to 20th	Night	7% 17% 40% 28% 8% 1	1000
	21st to end	Night	10% 12% 41% 28% 8% 1	1100

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