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 2024-11-04.

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% 42%	105564
	Night	6% 7% 3 8% 6% 5% 5% 4 6% 8% 41%	102097
Transparency	Day	37% 8% 16% 25% 12% 2	105287
	Night	37% 8% 16% 25% 12% 2	101964
Seeing	Day	11% 12% 31% 29% 14% 3	15635
	Night	10% 11% 35% 31% 11% 1	24894

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% 9% 6% 6% 6% 5% 8% 10% 28%	2219
	11th to 20th	Day	1 6% 4 14% 7% 6% 9% 7% 10% 9% 28%	2220
	21st to end	Day	2 6% 3 9% 7% 6% 6% 4 5% 8% 44%	2707
February	1st to 10th	Day	5% 10% 5% 12% 8% 7% 7% 5% 7% 8% 26%	1710
	11th to 20th	Day	4 9% 6% 11% 7% 8% 6% 5% 7% 10% 27%	1665
	21st to end	Day	4 10% 5% 12% 9% 7% 6% 6% 7% 7% 26%	1413
March	1st to 10th	Day	3 8% 4 11% 7% 7% 6% 5% 7% 11% 32%	3279
	11th to 20th	Day	5% 8% 3 8% 6% 4 4 4 7% 12% 39%	3490
	21st to end	Day	7% 17% 6% 16% 11% 5% 5% 4 5% 6% 19%	3841
April	1st to 10th	Day	6% 10% 3 8% 7% 7% 6% 5% 7% 8% 33%	2280
	11th to 20th	Day	9% 14% 4 11% 7% 5% 6% 4 6% 6% 29%	2427
	21st to end	Day	11% 11% 4 9% 5% 4 5% 4 7% 8% 33%	2470
May	1st to 10th	Day	15% 14% 5% 9% 5% 4 4 4 4 5% 30%	4430
	11th to 20th	Day	7% 7% 3 8% 5% 6% 6% 6% 7% 10% 34%	4388
	21st to end	Day	15% 9% 3 8% 6% 5% 5% 5% 7% 8% 29%	5122
June	1st to 10th	Day	14% 9% 3 6% 6% 5% 5% 4 6% 7% 35%	2850
	11th to 20th	Day	17% 8% 3 7% 5% 5% 5% 5% 6% 8% 33%	2850
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 44%	2850
July	1st to 10th	Day	4 3 2 6% 5% 5% 5% 4 7% 9% 49%	4740
	11th to 20th	Day	4 3 1 4 3 4 5% 4 6% 7% 58%	4740
	21st to end	Day	3 2 1 3 3 3 3 4 5% 7% 67%	5065
August	1st to 10th	Day	5% 4 2 5% 4 4 6% 5% 7% 8% 51%	4262
	11th to 20th	Day	5% 3 1 4 3 3 5% 4 7% 10% 54%	4028
	21st to end	Day	6% 4 1 4 3 3 4 3 5% 7% 60%	4521
September	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 4 7% 52%	2285
	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% 13% 6% 8% 6% 5% 4 4 6% 7% 32%	1512
	11th to 20th	Day	4 9% 3 10% 7% 7% 5% 4 5% 7% 39%	1520
	21st to end	Day	5% 10% 4 8% 7% 5% 7% 6% 8% 7% 33%	1520
December	1st to 10th	Day	4 10% 5% 11% 9% 9% 7% 5% 6% 6% 29%	1368
	11th to 20th	Day	4 9% 3 11% 7% 6% 6% 5% 7% 8% 34%	1685
	21st to end	Day	3 9% 3 7% 5% 5% 5% 4 6% 7% 47%	2442
January	1st to 10th	Night	2 9% 4 9% 6% 6% 8% 5% 8% 12% 32%	4726
	11th to 20th	Night	2 8% 5% 12% 8% 7% 6% 6% 8% 9% 28%	4740
	21st to end	Night	2 6% 3 9% 8% 6% 5% 4 7% 9% 40%	4982
February	1st to 10th	Night	5% 11% 4 10% 7% 7% 7% 5% 7% 8% 29%	2470
	11th to 20th	Night	3 9% 5% 10% 8% 7% 8% 5% 9% 8% 28%	2402
	21st to end	Night	3 10% 4 10% 8% 7% 6% 5% 7% 8% 32%	2041
March	1st to 10th	Night	3 8% 4 11% 8% 8% 8% 5% 7% 8% 29%	3588
	11th to 20th	Night	7% 6% 2 5% 4 4 5% 5% 6% 11% 45%	3490
	21st to end	Night	8% 16% 6% 15% 11% 8% 5% 4 5% 5% 17%	3811
April	1st to 10th	Night	7% 9% 4 9% 7% 7% 5% 4 6% 8% 34%	1900
	11th to 20th	Night	9% 12% 4 10% 6% 5% 6% 4 6% 8% 32%	1698
	21st to end	Night	9% 9% 4 8% 5% 5% 4 4 6% 7% 37%	1709
May	1st to 10th	Night	18% 13% 4 7% 5% 4 5% 3 5% 5% 32%	2540
	11th to 20th	Night	7% 6% 3 7% 6% 6% 5% 6% 8% 9% 37%	2517
	21st to end	Night	12% 7% 3 8% 6% 6% 6% 4 7% 8% 33%	2450
June	1st to 10th	Night	14% 7% 2 7% 3 4 4 4 6% 7% 42%	1330
	11th to 20th	Night	11% 6% 2 7% 6% 4 5% 4 5% 7% 43%	1330
	21st to end	Night	7% 3 1 5% 4 3 4 5% 7% 9% 53%	1330
July	1st to 10th	Night	3 3 2 5% 4 3 4 3 7% 9% 57%	2220
	11th to 20th	Night	3 2 1 3 2 3 4 4 5% 7% 64%	2220
	21st to end	Night	2 1 2 2 3 4 3 5% 7% 69%	2475
August	1st to 10th	Night	8% 3 2 5% 4 3 3 3 5% 8% 57%	2675
	11th to 20th	Night	4 3 2 6% 4 5% 5% 4 7% 10% 51%	2811
	21st to end	Night	9% 5% 2 5% 3 3 3 3 4 5% 58%	3146
September	1st to 10th	Night	10% 4 2 5% 3 3 4 3 5% 7% 55%	1895
	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% 4 6% 8% 34%	2639
	11th to 20th	Night	4 8% 3 9% 8% 7% 6% 5% 7% 9% 36%	2660
	21st to end	Night	4 10% 4 9% 6% 5% 6% 4 6% 9% 37%	2660
December	1st to 10th	Night	3 10% 4 10% 9% 8% 6% 5% 7% 8% 31%	2809
	11th to 20th	Night	2 9% 4 9% 9% 6% 6% 6% 7% 8% 34%	3506
	21st to end	Night	3 7% 3 6% 4 5% 4 4 6% 7% 50%	5214

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	42% 13% 21% 19% 4 1	2219
	11th to 20th	Day	45% 9% 14% 19% 12% 1	2220
	21st to end	Day	36% 12% 23% 23% 6%	2707
February	1st to 10th	Day	52% 10% 15% 16% 7%	1710
	11th to 20th	Day	48% 11% 16% 16% 8% 1	1674
	21st to end	Day	51% 10% 15% 14% 9% 1	1413
March	1st to 10th	Day	38% 13% 20% 24% 5%	3279
	11th to 20th	Day	34% 11% 24% 22% 8%	3490
	21st to end	Day	54% 18% 14% 10% 4	3841
April	1st to 10th	Day	44% 9% 18% 20% 8%	2280
	11th to 20th	Day	51% 8% 14% 20% 6% 1	2430
	21st to end	Day	45% 9% 15% 24% 6% 1	2470
May	1st to 10th	Day	52% 10% 14% 19% 5%	4430
	11th to 20th	Day	34% 14% 17% 26% 8%	4392
	21st to end	Day	44% 13% 15% 21% 6%	5122
June	1st to 10th	Day	44% 9% 18% 20% 9% 1	2850
	11th to 20th	Day	48% 7% 14% 20% 11% 1	2850
	21st to end	Day	32% 9% 18% 28% 11% 2	2850
July	1st to 10th	Day	30% 5% 19% 24% 17% 5%	4666
	11th to 20th	Day	23% 5% 13% 32% 21% 5%	4659
	21st to end	Day	16% 4 9% 29% 30% 12%	4905
August	1st to 10th	Day	29% 6% 10% 33% 19% 2	4247
	11th to 20th	Day	24% 5% 17% 39% 14% 1	4067
	21st to end	Day	23% 4 12% 40% 18% 2	4520
September	1st to 10th	Day	32% 6% 14% 23% 18% 7%	2285
	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% 9% 14% 18% 8% 1	1512
	11th to 20th	Day	40% 9% 20% 21% 8% 1	1520
	21st to end	Day	44% 11% 17% 19% 7% 1	1520
December	1st to 10th	Day	52% 7% 17% 16% 6% 1	1368
	11th to 20th	Day	43% 9% 21% 21% 4 1	1684
	21st to end	Day	35% 8% 13% 24% 12% 8%	2442
January	1st to 10th	Night	38% 13% 24% 19% 6% 1	4726
	11th to 20th	Night	46% 9% 15% 16% 11% 2	4740
	21st to end	Night	35% 11% 20% 27% 6% 1	4982
February	1st to 10th	Night	49% 7% 16% 16% 10% 2	2470
	11th to 20th	Night	47% 10% 16% 16% 10% 1	2403
	21st to end	Night	46% 7% 13% 23% 9% 2	2041
March	1st to 10th	Night	43% 13% 20% 15% 9%	3588
	11th to 20th	Night	30% 8% 26% 26% 9%	3490
	21st to end	Night	56% 16% 13% 10% 4 1	3811
April	1st to 10th	Night	44% 9% 16% 22% 8%	1900
	11th to 20th	Night	46% 8% 13% 21% 10% 2	1698
	21st to end	Night	43% 9% 13% 24% 9% 1	1709
May	1st to 10th	Night	48% 11% 11% 22% 8% 1	2540
	11th to 20th	Night	32% 13% 18% 26% 11% 1	2518
	21st to end	Night	39% 14% 19% 21% 6%	2450
June	1st to 10th	Night	39% 8% 18% 24% 9% 1	1330
	11th to 20th	Night	38% 8% 13% 24% 15% 2	1330
	21st to end	Night	26% 7% 19% 33% 13% 2	1330
July	1st to 10th	Night	23% 4 15% 35% 20% 2	2185
	11th to 20th	Night	20% 4 11% 34% 24% 7%	2178
	21st to end	Night	13% 4 9% 31% 32% 12%	2397
August	1st to 10th	Night	26% 5% 10% 34% 22% 3	2667
	11th to 20th	Night	28% 4 15% 35% 14% 3	2838
	21st to end	Night	29% 4 11% 34% 19% 3	3146
September	1st to 10th	Night	29% 5% 13% 26% 18% 9%	1895
	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	45% 8% 15% 21% 10% 1	2639
	11th to 20th	Night	41% 9% 21% 19% 10%	2660
	21st to end	Night	41% 9% 23% 19% 8% 1	2660
December	1st to 10th	Night	45% 12% 17% 16% 9% 1	2809
	11th to 20th	Night	41% 11% 23% 20% 4 1	3507
	21st to end	Night	31% 6% 15% 24% 16% 7%	5214

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	9% 14% 33% 28% 10% 6%	180
	11th to 20th	Day	7% 12% 38% 26% 15% 3	180
	21st to end	Day	7% 16% 38% 28% 10% 1	229
February	1st to 10th	Day	12% 18% 41% 20% 7% 1	270
	11th to 20th	Day	10% 13% 39% 27% 9% 3	270
	21st to end	Day	6% 10% 37% 33% 11% 2	225
March	1st to 10th	Day	9% 14% 36% 29% 10% 1	398
	11th to 20th	Day	6% 16% 38% 27% 9% 5%	460
	21st to end	Day	11% 12% 38% 25% 13% 2	506
April	1st to 10th	Day	10% 19% 38% 25% 8%	460
	11th to 20th	Day	12% 19% 36% 25% 8% 1	452
	21st to end	Day	16% 13% 30% 31% 9% 2	460
May	1st to 10th	Day	15% 8% 24% 32% 17% 4	653
	11th to 20th	Day	12% 9% 28% 30% 17% 4	675
	21st to end	Day	20% 10% 24% 23% 19% 5%	734
June	1st to 10th	Day	14% 13% 27% 28% 16% 2	680
	11th to 20th	Day	19% 15% 33% 20% 11% 1	680
	21st to end	Day	13% 10% 25% 27% 21% 4	680
July	1st to 10th	Day	7% 4 23% 43% 20% 3	671
	11th to 20th	Day	8% 7% 29% 36% 17% 3	668
	21st to end	Day	5% 6% 27% 35% 21% 6%	739
August	1st to 10th	Day	7% 7% 25% 37% 19% 5%	592
	11th to 20th	Day	8% 5% 26% 37% 20% 4	477
	21st to end	Day	8% 8% 29% 31% 20% 5%	539
September	1st to 10th	Day	12% 10% 30% 31% 15% 1	490
	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	14% 21% 35% 23% 8%	279
	11th to 20th	Day	9% 26% 36% 20% 7% 1	270
	21st to end	Day	9% 15% 43% 20% 10% 4	270
December	1st to 10th	Day	10% 12% 40% 30% 6% 3	198
	11th to 20th	Day	9% 24% 38% 24% 4	180
	21st to end	Day	10% 12% 29% 37% 10% 3	198
January	1st to 10th	Night	8% 17% 41% 25% 8% 1	950
	11th to 20th	Night	7% 17% 40% 26% 8% 1	950
	21st to end	Night	8% 17% 38% 27% 9% 1	968
February	1st to 10th	Night	9% 14% 33% 31% 11% 2	760
	11th to 20th	Night	6% 15% 44% 26% 8% 1	744
	21st to end	Night	7% 9% 36% 31% 14% 3	628
March	1st to 10th	Night	8% 13% 39% 31% 9% 1	760
	11th to 20th	Night	9% 10% 40% 29% 11% 2	760
	21st to end	Night	11% 10% 35% 31% 12% 1	831
April	1st to 10th	Night	9% 10% 40% 29% 10% 1	570
	11th to 20th	Night	13% 10% 36% 30% 9% 1	563
	21st to end	Night	14% 9% 30% 36% 11%	570
May	1st to 10th	Night	15% 7% 25% 35% 17% 1	570
	11th to 20th	Night	11% 6% 28% 36% 16% 2	561
	21st to end	Night	18% 9% 24% 31% 17% 2	435
June	1st to 10th	Night	15% 10% 26% 30% 18% 2	380
	11th to 20th	Night	14% 10% 32% 34% 10%	380
	21st to end	Night	9% 6% 25% 42% 16% 2	380
July	1st to 10th	Night	8% 4 24% 48% 16% 1	370
	11th to 20th	Night	6% 5% 28% 45% 14% 1	368
	21st to end	Night	4 4 24% 44% 23% 1	454
August	1st to 10th	Night	8% 4 23% 43% 20% 2	567
	11th to 20th	Night	8% 4 20% 44% 23% 1	564
	21st to end	Night	11% 5% 25% 39% 19% 1	627
September	1st to 10th	Night	11% 4 30% 38% 15% 2	570
	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%	943
	11th to 20th	Night	9% 17% 44% 22% 6% 1	950
	21st to end	Night	8% 13% 43% 29% 6%	950
December	1st to 10th	Night	8% 14% 40% 27% 10% 2	950
	11th to 20th	Night	6% 17% 40% 28% 8% 1	950
	21st to end	Night	10% 12% 40% 28% 8% 1	1045

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