Port Crescent State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Crescent State Park clear sky chart from 2005-11-06 to 2025-04-11.

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	13% 10% 4 9% 5% 5% 5% 4 6% 7% 33%	112911
	Night	14% 12% 5% 11% 6% 5% 4 3 5% 6% 29%	115494
Transparency	Day	50% 4 12% 22% 11% 1	116495
	Night	53% 4 11% 20% 11% 1	120050
Seeing	Day	18% 9% 29% 25% 13% 5%	15867
	Night	20% 9% 29% 28% 12% 2	25536

By Month

Percentage Cloud Cover SE (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	11% 14% 9% 24% 7% 5% 5% 3 4 3 15%	3617
	11th to 20th	Day	11% 16% 7% 18% 13% 8% 5% 4 5% 4 10%	3620
	21st to end	Day	16% 15% 7% 12% 7% 5% 4 3 5% 6% 19%	4260
February	1st to 10th	Day	12% 16% 4 12% 9% 6% 5% 4 5% 6% 22%	1800
	11th to 20th	Day	11% 13% 5% 11% 9% 7% 6% 4 6% 6% 24%	1838
	21st to end	Day	13% 12% 3 10% 5% 6% 5% 4 6% 8% 27%	1650
March	1st to 10th	Day	13% 10% 3 9% 7% 5% 4 4 5% 6% 34%	4607
	11th to 20th	Day	11% 12% 5% 10% 5% 5% 5% 4 7% 9% 29%	4980
	21st to end	Day	16% 11% 4 11% 6% 5% 5% 3 5% 6% 28%	5465
April	1st to 10th	Day	15% 11% 3 7% 5% 4 4 4 6% 8% 31%	2324
	11th to 20th	Day	16% 9% 2 7% 4 4 4 4 5% 7% 38%	2442
	21st to end	Day	15% 9% 4 7% 5% 5% 4 4 5% 7% 37%	2470
May	1st to 10th	Day	13% 8% 2 7% 5% 5% 4 4 6% 7% 39%	4082
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 6% 8% 38%	4081
	21st to end	Day	10% 7% 2 5% 4 3 4 3 5% 7% 50%	4778
June	1st to 10th	Day	10% 6% 2 5% 5% 4 5% 5% 6% 8% 43%	2850
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 5% 7% 9% 45%	2850
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 44%	2850
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 7% 9% 41%	4602
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 7% 9% 50%	4440
	21st to end	Day	7% 4 2 6% 5% 5% 5% 4 7% 9% 45%	4635
August	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 8% 9% 42%	4104
	11th to 20th	Day	12% 5% 2 6% 4 5% 4 5% 6% 8% 44%	4044
	21st to end	Day	9% 6% 2 6% 4 4 5% 4 6% 8% 45%	4532
September	1st to 10th	Day	11% 6% 2 7% 4 4 4 4 6% 8% 43%	2177
	11th to 20th	Day	13% 6% 2 6% 3 3 3 3 6% 8% 47%	2090
	21st to end	Day	15% 7% 3 6% 4 5% 5% 4 5% 7% 37%	2090
October	1st to 10th	Day	17% 8% 3 7% 4 4 4 3 5% 7% 39%	2010
	11th to 20th	Day	21% 11% 4 8% 5% 5% 5% 3 4 6% 27%	1900
	21st to end	Day	23% 12% 4 9% 5% 5% 5% 4 5% 7% 21%	1921
November	1st to 10th	Day	14% 14% 3 10% 5% 6% 4 3 6% 7% 28%	1762
	11th to 20th	Day	15% 16% 4 9% 6% 5% 6% 4 6% 7% 21%	1738
	21st to end	Day	17% 20% 6% 14% 6% 5% 4 3 5% 5% 16%	1600
December	1st to 10th	Day	15% 21% 12% 15% 7% 6% 5% 3 4 3 10%	2578
	11th to 20th	Day	14% 19% 7% 15% 9% 7% 5% 4 4 4 13%	2625
	21st to end	Day	25% 22% 6% 15% 6% 4 4 2 3 4 9%	3499
January	1st to 10th	Night	13% 13% 8% 24% 8% 5% 4 3 4 4 14%	6348
	11th to 20th	Night	11% 15% 7% 17% 13% 8% 5% 3 5% 5% 12%	6360
	21st to end	Night	12% 15% 7% 12% 7% 6% 6% 4 6% 6% 19%	6702
February	1st to 10th	Night	12% 16% 5% 12% 7% 6% 6% 4 6% 6% 20%	2600
	11th to 20th	Night	13% 14% 5% 11% 6% 5% 4 3 5% 6% 26%	2447
	21st to end	Night	14% 13% 4 11% 6% 6% 5% 4 5% 6% 25%	1980
March	1st to 10th	Night	13% 11% 4 8% 6% 4 4 3 5% 7% 37%	5245
	11th to 20th	Night	9% 10% 4 9% 5% 5% 5% 4 6% 9% 35%	4980
	21st to end	Night	16% 11% 4 10% 6% 4 4 3 4 5% 32%	5467
April	1st to 10th	Night	17% 13% 3 8% 5% 4 3 3 5% 6% 34%	2092
	11th to 20th	Night	17% 8% 2 6% 5% 4 4 3 5% 8% 37%	1693
	21st to end	Night	17% 9% 4 8% 4 5% 3 3 6% 6% 34%	1710
May	1st to 10th	Night	11% 9% 3 8% 4 5% 5% 4 5% 8% 38%	2813
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 4 6% 8% 38%	2812
	21st to end	Night	10% 4 2 6% 4 4 5% 4 6% 7% 47%	2775
June	1st to 10th	Night	14% 6% 3 8% 5% 4 3 4 5% 7% 42%	1330
	11th to 20th	Night	10% 5% 1 7% 5% 5% 4 4 6% 9% 44%	1330
	21st to end	Night	9% 7% 3 6% 5% 4 4 4 5% 8% 43%	1330
July	1st to 10th	Night	7% 6% 3 8% 4 4 5% 4 6% 8% 44%	2362
	11th to 20th	Night	9% 4 1 4 4 4 4 3 6% 8% 53%	2530
	21st to end	Night	6% 4 2 7% 4 4 5% 5% 6% 9% 47%	2920
August	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 46%	2825
	11th to 20th	Night	11% 6% 2 5% 3 4 4 4 7% 10% 45%	2785
	21st to end	Night	7% 5% 2 7% 5% 5% 5% 4 7% 8% 45%	3124
September	1st to 10th	Night	11% 6% 3 6% 5% 3 5% 3 5% 7% 46%	1981
	11th to 20th	Night	11% 6% 2 5% 4 3 4 3 4 6% 51%	2090
	21st to end	Night	15% 8% 3 7% 4 4 4 3 5% 7% 40%	2090
October	1st to 10th	Night	16% 7% 3 7% 5% 4 4 4 5% 7% 39%	2169
	11th to 20th	Night	21% 13% 3 8% 5% 5% 3 3 4 6% 30%	2280
	21st to end	Night	23% 13% 4 10% 5% 4 4 4 4 5% 24%	2674
November	1st to 10th	Night	15% 14% 4 8% 5% 4 4 3 5% 6% 32%	2536
	11th to 20th	Night	15% 16% 6% 13% 7% 5% 5% 4 5% 5% 20%	2660
	21st to end	Night	21% 19% 6% 12% 5% 5% 4 3 4 4 18%	2800
December	1st to 10th	Night	14% 19% 9% 17% 6% 5% 5% 3 4 5% 12%	4598
	11th to 20th	Night	12% 17% 7% 16% 9% 7% 5% 4 4 5% 15%	5582
	21st to end	Night	22% 20% 8% 13% 6% 5% 5% 3 4 4 10%	7474

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	72% 4 8% 10% 4 1	3618
	11th to 20th	Day	76% 4 4 8% 7%	3620
	21st to end	Day	67% 3 12% 9% 8% 1	4260
February	1st to 10th	Day	61% 5% 10% 18% 6%	1800
	11th to 20th	Day	61% 4 10% 16% 8% 1	1847
	21st to end	Day	55% 3 12% 21% 8% 1	1650
March	1st to 10th	Day	52% 3 14% 19% 10% 2	4607
	11th to 20th	Day	52% 3 14% 21% 8% 1	4980
	21st to end	Day	58% 3 11% 18% 9% 1	5465
April	1st to 10th	Day	53% 3 12% 20% 11% 1	2324
	11th to 20th	Day	47% 3 12% 22% 15% 1	2442
	21st to end	Day	48% 3 13% 20% 13% 2	2470
May	1st to 10th	Day	44% 2 11% 22% 18% 2	4120
	11th to 20th	Day	44% 3 14% 26% 11% 2	4085
	21st to end	Day	35% 3 12% 22% 21% 7%	4792
June	1st to 10th	Day	37% 5% 13% 27% 16% 1	2850
	11th to 20th	Day	35% 4 13% 28% 18% 2	2850
	21st to end	Day	37% 5% 13% 28% 16% 1	2850
July	1st to 10th	Day	40% 4 14% 24% 16% 2	4532
	11th to 20th	Day	30% 4 13% 38% 13% 1	4365
	21st to end	Day	34% 5% 15% 26% 18% 2	4488
August	1st to 10th	Day	37% 5% 14% 29% 14% 1	4091
	11th to 20th	Day	38% 4 18% 30% 10% 1	4083
	21st to end	Day	37% 4 13% 31% 13% 1	4531
September	1st to 10th	Day	39% 5% 14% 30% 11% 1	2177
	11th to 20th	Day	37% 4 13% 32% 14%	2090
	21st to end	Day	46% 4 15% 24% 10%	2090
October	1st to 10th	Day	35% 3 11% 36% 12% 2	3335
	11th to 20th	Day	50% 3 12% 22% 12%	3140
	21st to end	Day	54% 4 12% 22% 7%	3145
November	1st to 10th	Day	55% 4 11% 21% 9% 1	1762
	11th to 20th	Day	61% 5% 13% 13% 8%	1738
	21st to end	Day	70% 3 11% 13% 3	1600
December	1st to 10th	Day	76% 5% 10% 7% 1	2578
	11th to 20th	Day	73% 3 9% 11% 3	2621
	21st to end	Day	81% 3 6% 7% 3	3499
January	1st to 10th	Night	71% 4 9% 12% 4 1	6348
	11th to 20th	Night	72% 4 9% 9% 5% 1	6360
	21st to end	Night	62% 4 10% 14% 9%	6702
February	1st to 10th	Night	61% 4 9% 18% 7% 1	2600
	11th to 20th	Night	58% 4 10% 19% 7% 1	2449
	21st to end	Night	60% 3 11% 17% 8%	1980
March	1st to 10th	Night	48% 2 15% 23% 10% 1	5245
	11th to 20th	Night	47% 3 18% 22% 9% 1	4980
	21st to end	Night	54% 3 10% 20% 11% 1	5467
April	1st to 10th	Night	52% 3 8% 21% 14% 2	2092
	11th to 20th	Night	45% 3 10% 22% 18% 2	1693
	21st to end	Night	50% 3 8% 20% 16% 3	1710
May	1st to 10th	Night	44% 3 11% 22% 16% 4	2840
	11th to 20th	Night	44% 3 10% 27% 14% 3	2813
	21st to end	Night	36% 2 11% 25% 18% 7%	2782
June	1st to 10th	Night	42% 3 8% 28% 17% 2	1330
	11th to 20th	Night	36% 5% 13% 22% 22% 3	1330
	21st to end	Night	38% 3 12% 25% 19% 2	1330
July	1st to 10th	Night	38% 4 12% 25% 16% 6%	2323
	11th to 20th	Night	29% 4 13% 37% 16% 1	2482
	21st to end	Night	32% 5% 18% 23% 20% 2	2827
August	1st to 10th	Night	36% 4 14% 32% 14% 1	2814
	11th to 20th	Night	34% 4 15% 30% 14% 3	2812
	21st to end	Night	35% 5% 13% 32% 14% 1	3124
September	1st to 10th	Night	38% 5% 11% 30% 16% 1	1981
	11th to 20th	Night	34% 3 11% 35% 16% 1	2090
	21st to end	Night	44% 3 12% 30% 11% 1	2090
October	1st to 10th	Night	31% 4 10% 33% 21% 1	3624
	11th to 20th	Night	50% 2 8% 25% 14%	3779
	21st to end	Night	51% 3 10% 26% 9%	4400
November	1st to 10th	Night	52% 4 10% 23% 10% 1	2536
	11th to 20th	Night	64% 4 12% 15% 6% 1	2660
	21st to end	Night	68% 4 13% 13% 3 1	2800
December	1st to 10th	Night	71% 4 12% 9% 3	4598
	11th to 20th	Night	69% 3 10% 12% 6%	5585
	21st to end	Night	76% 3 8% 8% 4	7474

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	19% 14% 42% 18% 6% 1	300
	11th to 20th	Day	20% 16% 40% 18% 6% 1	300
	21st to end	Day	23% 12% 38% 21% 5% 1	330
February	1st to 10th	Day	20% 21% 38% 15% 4 1	300
	11th to 20th	Day	19% 21% 44% 14% 2	300
	21st to end	Day	23% 23% 35% 16% 2	249
March	1st to 10th	Day	22% 19% 39% 16% 3 1	349
	11th to 20th	Day	21% 16% 32% 24% 6% 2	500
	21st to end	Day	27% 12% 32% 22% 6% 1	550
April	1st to 10th	Day	24% 13% 36% 21% 6% 1	500
	11th to 20th	Day	27% 12% 28% 18% 11% 4	452
	21st to end	Day	24% 9% 33% 23% 8% 3	460
May	1st to 10th	Day	20% 11% 32% 24% 11% 3	463
	11th to 20th	Day	17% 7% 29% 26% 15% 7%	487
	21st to end	Day	13% 5% 27% 31% 17% 6%	595
June	1st to 10th	Day	14% 6% 33% 29% 15% 4	680
	11th to 20th	Day	13% 6% 30% 33% 14% 4	680
	21st to end	Day	15% 5% 31% 31% 15% 4	680
July	1st to 10th	Day	11% 4 22% 32% 23% 8%	671
	11th to 20th	Day	13% 4 24% 34% 18% 8%	668
	21st to end	Day	10% 3 23% 36% 20% 8%	636
August	1st to 10th	Day	13% 3 20% 29% 23% 13%	486
	11th to 20th	Day	11% 3 17% 32% 24% 14%	479
	21st to end	Day	16% 4 19% 30% 24% 8%	539
September	1st to 10th	Day	13% 5% 26% 28% 19% 10%	490
	11th to 20th	Day	13% 4 18% 26% 24% 15%	490
	21st to end	Day	18% 6% 25% 23% 19% 8%	490
October	1st to 10th	Day	22% 8% 25% 22% 16% 6%	490
	11th to 20th	Day	27% 12% 28% 25% 6% 1	490
	21st to end	Day	31% 13% 32% 19% 5% 1	370
November	1st to 10th	Day	22% 16% 34% 20% 7% 2	300
	11th to 20th	Day	23% 17% 34% 20% 6% 1	268
	21st to end	Day	23% 18% 35% 21% 5%	200
December	1st to 10th	Day	26% 14% 37% 20% 5%	200
	11th to 20th	Day	27% 21% 34% 14% 4 1	200
	21st to end	Day	32% 15% 33% 16% 4	225
January	1st to 10th	Night	22% 13% 36% 22% 6% 1	1000
	11th to 20th	Night	22% 16% 35% 21% 6% 1	1000
	21st to end	Night	17% 11% 37% 26% 9%	975
February	1st to 10th	Night	22% 14% 37% 22% 4	800
	11th to 20th	Night	22% 14% 35% 22% 7%	783
	21st to end	Night	21% 16% 37% 22% 4	660
March	1st to 10th	Night	18% 11% 36% 26% 8% 1	800
	11th to 20th	Night	17% 13% 38% 24% 7% 1	800
	21st to end	Night	24% 10% 29% 27% 9% 1	880
April	1st to 10th	Night	24% 11% 36% 22% 7%	693
	11th to 20th	Night	23% 10% 31% 24% 11% 2	565
	21st to end	Night	24% 8% 24% 34% 10% 1	570
May	1st to 10th	Night	17% 4 27% 39% 11% 2	570
	11th to 20th	Night	19% 6% 22% 36% 16% 1	561
	21st to end	Night	13% 3 28% 34% 20% 1	509
June	1st to 10th	Night	16% 5% 25% 37% 17% 1	380
	11th to 20th	Night	14% 3 27% 39% 17% 1	380
	21st to end	Night	13% 3 24% 37% 20% 2	380
July	1st to 10th	Night	9% 1 19% 43% 26% 1	453
	11th to 20th	Night	11% 2 17% 38% 26% 5%	552
	21st to end	Night	9% 1 19% 44% 24% 3	624
August	1st to 10th	Night	10% 2 12% 41% 32% 3	567
	11th to 20th	Night	11% 2 14% 33% 33% 7%	564
	21st to end	Night	13% 3 18% 36% 26% 4	627
September	1st to 10th	Night	14% 4 22% 32% 23% 6%	682
	11th to 20th	Night	13% 3 17% 34% 24% 8%	760
	21st to end	Night	18% 6% 20% 32% 17% 7%	760
October	1st to 10th	Night	20% 7% 27% 28% 16% 2	760
	11th to 20th	Night	28% 11% 26% 28% 7% 1	760
	21st to end	Night	30% 8% 29% 27% 5% 1	836
November	1st to 10th	Night	23% 13% 28% 24% 11% 1	780
	11th to 20th	Night	24% 14% 33% 22% 8%	800
	21st to end	Night	30% 14% 31% 21% 4	800
December	1st to 10th	Night	25% 16% 36% 17% 6%	805
	11th to 20th	Night	24% 16% 37% 19% 4 1	1000
	21st to end	Night	29% 13% 33% 21% 3	1100

Page generated at 2025-04-08 09:17:29. Version ac07

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