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 2024-10-24.

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% 3 8% 5% 5% 5% 4 6% 7% 35%	101104
	Night	14% 11% 4 10% 6% 5% 4 3 5% 6% 31%	97679
Transparency	Day	49% 4 12% 22% 11% 1	100899
	Night	53% 4 11% 21% 10% 1	97555
Seeing	Day	18% 9% 29% 26% 13% 5%	15370
	Night	20% 9% 29% 28% 12% 2	24819

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	16% 17% 10% 17% 6% 5% 5% 3 4 3 14%	2527
	11th to 20th	Day	13% 18% 8% 19% 14% 8% 3 3 4 4 7%	2530
	21st to end	Day	20% 17% 6% 12% 8% 5% 4 3 5% 5% 14%	2970
February	1st to 10th	Day	12% 16% 4 12% 9% 6% 5% 4 5% 6% 21%	1710
	11th to 20th	Day	11% 13% 4 11% 9% 7% 6% 4 6% 6% 24%	1743
	21st to end	Day	14% 12% 3 10% 5% 6% 5% 4 6% 8% 27%	1570
March	1st to 10th	Day	16% 13% 4 9% 6% 5% 4 4 5% 5% 30%	3205
	11th to 20th	Day	11% 12% 5% 10% 5% 5% 5% 4 6% 7% 31%	3480
	21st to end	Day	15% 10% 4 11% 6% 5% 5% 4 5% 6% 29%	3815
April	1st to 10th	Day	15% 11% 3 8% 5% 4 4 4 6% 8% 31%	2208
	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	24% 12% 4 9% 5% 5% 5% 4 5% 6% 21%	1849
November	1st to 10th	Day	13% 14% 3 10% 5% 6% 4 4 6% 7% 28%	1672
	11th to 20th	Day	14% 17% 5% 9% 7% 5% 5% 4 6% 7% 21%	1652
	21st to end	Day	17% 20% 5% 14% 6% 5% 3 3 5% 5% 17%	1520
December	1st to 10th	Day	13% 22% 10% 14% 8% 6% 5% 4 4 4 12%	1511
	11th to 20th	Day	15% 17% 6% 13% 8% 6% 4 4 4 5% 17%	1675
	21st to end	Day	25% 24% 7% 13% 6% 5% 4 2 3 3 8%	2440
January	1st to 10th	Night	16% 15% 8% 16% 7% 5% 4 3 4 4 17%	4428
	11th to 20th	Night	13% 15% 8% 19% 14% 8% 4 3 3 3 9%	4440
	21st to end	Night	17% 16% 8% 14% 8% 7% 5% 3 5% 4 13%	4688
February	1st to 10th	Night	13% 16% 5% 12% 7% 5% 6% 4 6% 6% 20%	2470
	11th to 20th	Night	13% 14% 5% 11% 6% 5% 4 3 5% 7% 26%	2322
	21st to end	Night	15% 14% 4 11% 6% 6% 5% 4 5% 6% 26%	1884
March	1st to 10th	Night	12% 12% 4 7% 4 4 5% 3 4 7% 39%	3647
	11th to 20th	Night	9% 11% 4 9% 6% 5% 5% 4 5% 6% 38%	3480
	21st to end	Night	14% 11% 5% 10% 6% 5% 5% 3 5% 6% 32%	3817
April	1st to 10th	Night	18% 13% 3 7% 5% 3 3 3 5% 6% 34%	1988
	11th to 20th	Night	17% 7% 2 6% 5% 4 4 3 6% 8% 37%	1687
	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	24% 13% 4 10% 5% 4 4 4 4 5% 23%	2571
November	1st to 10th	Night	15% 14% 4 8% 5% 4 4 3 5% 6% 32%	2406
	11th to 20th	Night	15% 16% 6% 13% 7% 5% 5% 4 5% 5% 20%	2527
	21st to end	Night	21% 19% 5% 12% 5% 5% 4 3 4 4 18%	2660
December	1st to 10th	Night	18% 20% 7% 13% 6% 5% 4 3 4 6% 13%	2664
	11th to 20th	Night	14% 16% 6% 16% 8% 6% 5% 4 5% 7% 13%	3522
	21st to end	Night	24% 22% 9% 11% 5% 5% 5% 3 3 4 9%	5222

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 11% 9% 3	2528
	11th to 20th	Day	82% 4 5% 7% 2	2530
	21st to end	Day	73% 3 13% 8% 3	2970
February	1st to 10th	Day	62% 5% 10% 18% 5%	1710
	11th to 20th	Day	60% 4 11% 16% 8% 1	1752
	21st to end	Day	55% 3 12% 20% 8% 1	1570
March	1st to 10th	Day	57% 2 11% 22% 7% 1	3205
	11th to 20th	Day	54% 3 11% 22% 8% 2	3480
	21st to end	Day	57% 3 11% 18% 10% 1	3815
April	1st to 10th	Day	53% 3 12% 20% 11% 1	2208
	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	47% 3 10% 27% 11% 2	2010
	11th to 20th	Day	57% 3 12% 20% 7%	1900
	21st to end	Day	62% 5% 12% 16% 5% 1	1849
November	1st to 10th	Day	55% 4 11% 21% 9% 1	1672
	11th to 20th	Day	61% 5% 14% 12% 8%	1652
	21st to end	Day	69% 3 11% 13% 3	1520
December	1st to 10th	Day	74% 4 11% 10% 2	1511
	11th to 20th	Day	68% 4 11% 14% 3	1671
	21st to end	Day	82% 2 7% 7% 1	2440
January	1st to 10th	Night	67% 4 11% 14% 4	4428
	11th to 20th	Night	77% 3 9% 9% 3	4440
	21st to end	Night	71% 5% 10% 11% 3	4688
February	1st to 10th	Night	62% 4 9% 18% 6% 1	2470
	11th to 20th	Night	58% 5% 11% 19% 7% 1	2324
	21st to end	Night	60% 3 11% 17% 9%	1884
March	1st to 10th	Night	47% 2 15% 29% 7% 1	3647
	11th to 20th	Night	46% 3 15% 23% 12% 1	3480
	21st to end	Night	54% 3 11% 23% 8% 1	3817
April	1st to 10th	Night	52% 3 8% 21% 14% 2	1988
	11th to 20th	Night	45% 3 10% 22% 18% 2	1687
	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	44% 4 11% 25% 15% 1	2169
	11th to 20th	Night	57% 3 10% 22% 8% 1	2280
	21st to end	Night	61% 3 10% 18% 7%	2571
November	1st to 10th	Night	51% 4 10% 23% 10% 1	2406
	11th to 20th	Night	64% 4 12% 15% 5% 1	2527
	21st to end	Night	67% 4 13% 13% 3	2660
December	1st to 10th	Night	70% 3 10% 13% 4	2664
	11th to 20th	Night	68% 4 13% 11% 3	3525
	21st to end	Night	78% 3 10% 6% 2	5222

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	20% 14% 41% 17% 7% 1	270
	11th to 20th	Day	21% 16% 38% 19% 6% 1	270
	21st to end	Day	25% 9% 38% 22% 5% 1	297
February	1st to 10th	Day	20% 20% 39% 16% 4 1	270
	11th to 20th	Day	19% 20% 43% 15% 2	270
	21st to end	Day	22% 25% 35% 16% 2	225
March	1st to 10th	Day	23% 18% 38% 16% 4 1	316
	11th to 20th	Day	20% 16% 31% 24% 7% 2	460
	21st to end	Day	27% 11% 32% 22% 7% 1	506
April	1st to 10th	Day	22% 13% 36% 21% 7% 1	460
	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% 12% 32% 19% 5% 1	346
November	1st to 10th	Day	21% 14% 36% 20% 7% 2	270
	11th to 20th	Day	21% 18% 34% 19% 6% 2	242
	21st to end	Day	23% 18% 34% 21% 4	180
December	1st to 10th	Day	24% 14% 38% 19% 4	180
	11th to 20th	Day	27% 20% 34% 14% 3 1	180
	21st to end	Day	30% 15% 35% 15% 4	202
January	1st to 10th	Night	23% 13% 35% 22% 6% 1	950
	11th to 20th	Night	22% 15% 35% 21% 6% 1	950
	21st to end	Night	18% 9% 37% 26% 9%	927
February	1st to 10th	Night	22% 14% 37% 23% 4	760
	11th to 20th	Night	22% 14% 34% 23% 7%	743
	21st to end	Night	22% 15% 38% 22% 4	628
March	1st to 10th	Night	18% 11% 35% 26% 9% 1	760
	11th to 20th	Night	17% 13% 38% 24% 7% 1	760
	21st to end	Night	24% 10% 29% 28% 9% 1	836
April	1st to 10th	Night	24% 10% 35% 22% 8%	659
	11th to 20th	Night	23% 10% 31% 24% 11% 2	563
	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	31% 8% 29% 27% 4 1	805
November	1st to 10th	Night	23% 13% 28% 25% 11% 1	740
	11th to 20th	Night	23% 15% 33% 21% 8%	760
	21st to end	Night	29% 14% 31% 22% 4	760
December	1st to 10th	Night	26% 15% 35% 18% 6%	764
	11th to 20th	Night	24% 15% 36% 19% 4 1	950
	21st to end	Night	29% 13% 34% 21% 3	1045

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