Presque Isle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Presque Isle clear sky chart from 2005-11-06 to 2026-06-16.

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	17% 10% 3 8% 5% 5% 5% 4 6% 7% 30%	137382
	Night	17% 11% 4 9% 5% 5% 5% 4 5% 6% 31%	134786
Transparency	Day	52% 6% 13% 19% 9% 1	140853
	Night	53% 6% 12% 19% 10% 1	139405
Seeing	Day	22% 12% 29% 24% 11% 2	18079
	Night	22% 10% 31% 28% 8% 1	26134

By Month

Percentage Cloud Cover NE (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% 16% 7% 13% 6% 6% 4 3 4 6% 23%	4133
	11th to 20th	Day	12% 14% 6% 15% 6% 5% 5% 4 6% 5% 21%	4650
	21st to end	Day	5% 9% 4 11% 7% 8% 7% 5% 7% 8% 28%	5124
February	1st to 10th	Day	10% 14% 5% 8% 7% 8% 5% 5% 7% 6% 26%	1880
	11th to 20th	Day	14% 12% 5% 11% 6% 6% 6% 4 5% 5% 27%	1864
	21st to end	Day	11% 10% 4 9% 6% 6% 6% 5% 5% 6% 30%	1730
March	1st to 10th	Day	19% 15% 4 9% 6% 5% 4 3 5% 5% 25%	4661
	11th to 20th	Day	17% 14% 5% 10% 6% 5% 4 3 5% 6% 24%	5090
	21st to end	Day	20% 15% 4 9% 5% 5% 5% 3 4 5% 24%	5587
April	1st to 10th	Day	19% 12% 4 9% 6% 5% 5% 4 5% 5% 27%	2511
	11th to 20th	Day	19% 10% 3 7% 6% 5% 5% 4 5% 6% 32%	2702
	21st to end	Day	23% 11% 3 6% 4 4 4 3 5% 6% 32%	2730
May	1st to 10th	Day	24% 10% 3 8% 5% 5% 5% 4 5% 6% 24%	7639
	11th to 20th	Day	22% 8% 3 7% 5% 5% 5% 4 6% 7% 29%	7999
	21st to end	Day	18% 8% 3 8% 6% 5% 6% 4 6% 7% 30%	9716
June	1st to 10th	Day	21% 9% 2 7% 5% 5% 5% 4 6% 7% 28%	3150
	11th to 20th	Day	20% 7% 3 7% 5% 5% 4 3 6% 8% 33%	3075
	21st to end	Day	23% 9% 3 7% 5% 6% 6% 4 5% 7% 25%	3000
July	1st to 10th	Day	15% 7% 3 8% 6% 6% 6% 5% 8% 9% 28%	6820
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 4 6% 8% 36%	6668
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 39%	6926
August	1st to 10th	Day	16% 6% 3 7% 5% 6% 6% 5% 7% 8% 33%	4240
	11th to 20th	Day	14% 7% 3 8% 6% 6% 6% 4 7% 8% 31%	4175
	21st to end	Day	16% 6% 2 7% 5% 5% 5% 4 6% 8% 37%	4675
September	1st to 10th	Day	14% 7% 2 6% 4 4 4 3 5% 8% 43%	2371
	11th to 20th	Day	15% 6% 2 4 4 4 4 3 4 6% 49%	2200
	21st to end	Day	17% 5% 1 6% 4 4 4 4 5% 7% 41%	2200
October	1st to 10th	Day	16% 8% 3 6% 5% 5% 3 3 4 6% 40%	2095
	11th to 20th	Day	20% 9% 3 8% 4 4 4 3 5% 7% 33%	1985
	21st to end	Day	23% 10% 4 7% 4 5% 5% 4 5% 7% 26%	1980
November	1st to 10th	Day	18% 10% 3 8% 5% 6% 4 4 5% 5% 31%	1845
	11th to 20th	Day	18% 12% 4 8% 5% 5% 5% 4 5% 6% 28%	1680
	21st to end	Day	19% 13% 3 10% 4 5% 4 4 5% 7% 25%	1680
December	1st to 10th	Day	18% 13% 4 9% 5% 4 4 4 5% 6% 28%	2360
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 6% 31%	2688
	21st to end	Day	16% 15% 5% 11% 5% 5% 4 3 5% 6% 25%	3553
January	1st to 10th	Night	12% 16% 7% 12% 7% 5% 5% 4 5% 5% 20%	8771
	11th to 20th	Night	13% 15% 6% 12% 7% 6% 5% 4 5% 5% 20%	8235
	21st to end	Night	5% 9% 5% 11% 7% 6% 7% 5% 6% 7% 32%	9057
February	1st to 10th	Night	11% 13% 5% 9% 7% 6% 5% 4 5% 6% 28%	2740
	11th to 20th	Night	12% 15% 5% 9% 8% 7% 5% 4 4 5% 26%	2641
	21st to end	Night	12% 14% 2 9% 6% 4 5% 4 5% 5% 34%	2076
March	1st to 10th	Night	22% 13% 4 10% 5% 5% 5% 3 3 5% 25%	5399
	11th to 20th	Night	16% 13% 5% 9% 5% 5% 5% 4 5% 7% 26%	5089
	21st to end	Night	26% 12% 4 7% 3 4 3 3 4 6% 28%	5587
April	1st to 10th	Night	23% 13% 3 8% 5% 4 3 3 4 4 31%	2105
	11th to 20th	Night	22% 8% 3 7% 4 4 4 3 5% 6% 33%	1868
	21st to end	Night	23% 11% 3 6% 4 5% 4 3 5% 5% 31%	1890
May	1st to 10th	Night	25% 12% 3 7% 4 4 4 4 5% 6% 26%	5259
	11th to 20th	Night	22% 7% 2 8% 5% 5% 5% 4 5% 5% 32%	4916
	21st to end	Night	18% 8% 3 7% 4 3 4 3 6% 6% 38%	4491
June	1st to 10th	Night	24% 6% 2 6% 4 5% 5% 4 5% 6% 32%	1470
	11th to 20th	Night	17% 5% 2 6% 5% 4 5% 5% 7% 8% 36%	1435
	21st to end	Night	22% 10% 4 7% 5% 4 4 3 5% 6% 30%	1400
July	1st to 10th	Night	15% 7% 3 8% 5% 5% 5% 4 6% 7% 35%	3160
	11th to 20th	Night	16% 6% 2 6% 4 5% 5% 4 7% 8% 37%	3289
	21st to end	Night	10% 6% 3 7% 5% 5% 6% 4 7% 8% 40%	3926
August	1st to 10th	Night	17% 7% 3 8% 6% 5% 5% 4 5% 8% 33%	2878
	11th to 20th	Night	12% 6% 2 8% 6% 5% 5% 5% 7% 9% 35%	2872
	21st to end	Night	17% 5% 2 6% 4 4 4 3 4 6% 46%	3223
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 2 5% 7% 46%	2025
	11th to 20th	Night	14% 6% 2 6% 4 3 3 3 4 6% 48%	2200
	21st to end	Night	17% 5% 2 5% 4 4 4 4 5% 6% 45%	2200
October	1st to 10th	Night	18% 7% 2 5% 3 3 4 3 5% 7% 43%	2305
	11th to 20th	Night	18% 10% 2 7% 4 4 4 4 5% 5% 36%	2412
	21st to end	Night	21% 10% 3 7% 4 4 4 3 5% 6% 32%	2860
November	1st to 10th	Night	20% 10% 3 6% 4 4 4 4 5% 6% 32%	2672
	11th to 20th	Night	19% 11% 3 8% 4 5% 4 3 5% 6% 31%	2940
	21st to end	Night	20% 11% 3 9% 6% 5% 5% 3 5% 6% 27%	2940
December	1st to 10th	Night	16% 12% 5% 10% 7% 6% 6% 5% 6% 5% 24%	5047
	11th to 20th	Night	21% 11% 3 8% 5% 4 4 3 5% 6% 31%	5741
	21st to end	Night	18% 12% 4 11% 6% 5% 4 4 5% 6% 25%	7667

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	63% 5% 10% 16% 6%	4134
	11th to 20th	Day	62% 6% 10% 17% 6%	4680
	21st to end	Day	48% 8% 11% 16% 16%	5124
February	1st to 10th	Day	56% 6% 12% 16% 9% 1	1880
	11th to 20th	Day	58% 6% 12% 16% 7% 1	1872
	21st to end	Day	51% 7% 12% 20% 9% 2	1730
March	1st to 10th	Day	61% 5% 8% 9% 14% 3	4665
	11th to 20th	Day	60% 6% 15% 11% 7% 1	5090
	21st to end	Day	62% 4 6% 18% 9% 2	5587
April	1st to 10th	Day	57% 5% 11% 16% 8% 2	2511
	11th to 20th	Day	50% 6% 13% 19% 12% 1	2702
	21st to end	Day	54% 5% 9% 18% 11% 3	2730
May	1st to 10th	Day	57% 6% 10% 18% 8%	7651
	11th to 20th	Day	53% 6% 13% 20% 7% 2	8003
	21st to end	Day	51% 6% 11% 17% 14% 1	9717
June	1st to 10th	Day	53% 6% 13% 16% 10% 1	3150
	11th to 20th	Day	49% 6% 14% 18% 12% 1	3075
	21st to end	Day	57% 8% 12% 15% 8% 1	3000
July	1st to 10th	Day	50% 7% 17% 18% 7%	6745
	11th to 20th	Day	45% 7% 15% 28% 5%	6587
	21st to end	Day	41% 7% 16% 29% 7%	6728
August	1st to 10th	Day	47% 8% 17% 22% 6%	4226
	11th to 20th	Day	48% 9% 16% 22% 5%	4214
	21st to end	Day	43% 7% 15% 24% 11%	4675
September	1st to 10th	Day	39% 7% 16% 26% 12%	2371
	11th to 20th	Day	38% 5% 13% 29% 15% 1	2200
	21st to end	Day	42% 7% 12% 27% 12%	2200
October	1st to 10th	Day	49% 5% 13% 27% 6%	3407
	11th to 20th	Day	48% 4 12% 28% 8%	3213
	21st to end	Day	47% 5% 15% 20% 12%	3180
November	1st to 10th	Day	54% 5% 13% 20% 7%	1845
	11th to 20th	Day	55% 8% 11% 16% 9% 1	1680
	21st to end	Day	59% 7% 16% 15% 4	1680
December	1st to 10th	Day	57% 6% 17% 12% 9%	2360
	11th to 20th	Day	52% 6% 11% 19% 9% 3	2688
	21st to end	Day	60% 5% 11% 11% 10% 1	3553
January	1st to 10th	Night	65% 6% 12% 12% 6%	8771
	11th to 20th	Night	65% 6% 9% 14% 6%	8280
	21st to end	Night	50% 5% 8% 19% 17% 1	9057
February	1st to 10th	Night	55% 5% 11% 17% 10% 1	2740
	11th to 20th	Night	61% 5% 9% 16% 8% 1	2644
	21st to end	Night	53% 5% 9% 19% 12% 1	2076
March	1st to 10th	Night	62% 4 8% 14% 10% 2	5408
	11th to 20th	Night	57% 6% 16% 13% 8%	5090
	21st to end	Night	59% 3 6% 18% 14% 1	5587
April	1st to 10th	Night	56% 4 9% 17% 11% 3	2105
	11th to 20th	Night	51% 5% 11% 18% 14% 1	1868
	21st to end	Night	54% 5% 8% 17% 14% 2	1890
May	1st to 10th	Night	57% 6% 11% 16% 9% 1	5265
	11th to 20th	Night	52% 6% 10% 22% 9% 1	4917
	21st to end	Night	45% 6% 10% 21% 15% 2	4492
June	1st to 10th	Night	52% 5% 13% 21% 9% 1	1470
	11th to 20th	Night	43% 9% 14% 21% 12% 1	1435
	21st to end	Night	56% 6% 11% 17% 9% 1	1400
July	1st to 10th	Night	48% 6% 20% 21% 7%	3125
	11th to 20th	Night	44% 8% 17% 27% 4	3247
	21st to end	Night	41% 8% 17% 25% 9%	3809
August	1st to 10th	Night	51% 7% 14% 22% 6%	2868
	11th to 20th	Night	44% 10% 21% 17% 7%	2899
	21st to end	Night	41% 6% 14% 24% 14% 1	3223
September	1st to 10th	Night	38% 6% 14% 29% 12% 1	2025
	11th to 20th	Night	38% 6% 14% 29% 14%	2200
	21st to end	Night	40% 7% 12% 26% 15% 1	2200
October	1st to 10th	Night	47% 4 12% 27% 9%	3773
	11th to 20th	Night	47% 5% 12% 28% 8%	3923
	21st to end	Night	43% 6% 19% 21% 12%	4610
November	1st to 10th	Night	52% 6% 14% 20% 8%	2672
	11th to 20th	Night	53% 7% 13% 17% 10% 1	2940
	21st to end	Night	57% 8% 14% 15% 6% 1	2940
December	1st to 10th	Night	61% 5% 12% 18% 4	5047
	11th to 20th	Night	54% 5% 10% 19% 11% 1	5742
	21st to end	Night	59% 5% 10% 16% 9% 1	7667

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% 17% 29% 26% 8%	220
	11th to 20th	Day	24% 20% 28% 18% 9% 1	220
	21st to end	Day	13% 14% 38% 22% 8% 4	242
February	1st to 10th	Day	20% 14% 30% 26% 8% 2	420
	11th to 20th	Day	17% 14% 40% 23% 6% 1	437
	21st to end	Day	17% 17% 35% 24% 7%	446
March	1st to 10th	Day	25% 14% 31% 24% 7%	540
	11th to 20th	Day	21% 13% 33% 24% 8% 1	540
	21st to end	Day	23% 15% 26% 26% 8% 2	594
April	1st to 10th	Day	26% 15% 28% 21% 9% 1	540
	11th to 20th	Day	24% 11% 30% 24% 9% 2	532
	21st to end	Day	27% 12% 26% 23% 9% 2	540
May	1st to 10th	Day	27% 13% 28% 21% 10% 1	543
	11th to 20th	Day	27% 14% 27% 21% 10% 3	653
	21st to end	Day	22% 15% 31% 24% 8% 1	845
June	1st to 10th	Day	23% 12% 29% 26% 9% 2	780
	11th to 20th	Day	22% 11% 27% 25% 13% 2	755
	21st to end	Day	24% 8% 31% 25% 10% 2	730
July	1st to 10th	Day	17% 7% 31% 28% 14% 2	720
	11th to 20th	Day	16% 7% 28% 33% 15% 2	657
	21st to end	Day	16% 5% 31% 31% 15% 2	576
August	1st to 10th	Day	17% 7% 27% 29% 15% 6%	526
	11th to 20th	Day	16% 9% 20% 29% 22% 4	519
	21st to end	Day	18% 11% 22% 27% 17% 5%	583
September	1st to 10th	Day	15% 9% 29% 26% 16% 5%	530
	11th to 20th	Day	19% 10% 23% 26% 14% 8%	530
	21st to end	Day	19% 10% 29% 22% 13% 7%	530
October	1st to 10th	Day	19% 11% 27% 22% 16% 5%	472
	11th to 20th	Day	24% 17% 27% 19% 10% 3	420
	21st to end	Day	28% 14% 29% 21% 7% 1	462
November	1st to 10th	Day	28% 16% 30% 19% 7% 1	425
	11th to 20th	Day	28% 14% 29% 20% 7% 2	430
	21st to end	Day	27% 13% 30% 24% 6%	430
December	1st to 10th	Day	21% 13% 33% 19% 12% 2	230
	11th to 20th	Day	22% 18% 37% 17% 5% 1	220
	21st to end	Day	22% 19% 29% 20% 9% 1	242
January	1st to 10th	Night	22% 12% 35% 27% 4	939
	11th to 20th	Night	24% 15% 30% 24% 6%	840
	21st to end	Night	15% 11% 39% 28% 7%	924
February	1st to 10th	Night	18% 11% 41% 23% 6% 1	840
	11th to 20th	Night	21% 14% 36% 23% 5%	823
	21st to end	Night	20% 10% 37% 27% 5%	692
March	1st to 10th	Night	21% 11% 37% 29% 3	840
	11th to 20th	Night	23% 13% 32% 25% 6% 1	840
	21st to end	Night	22% 9% 36% 26% 6% 1	924
April	1st to 10th	Night	29% 11% 30% 24% 5%	801
	11th to 20th	Night	26% 10% 30% 25% 7%	624
	21st to end	Night	29% 10% 28% 25% 8%	630
May	1st to 10th	Night	26% 9% 32% 27% 6%	630
	11th to 20th	Night	25% 9% 33% 26% 7% 1	598
	21st to end	Night	22% 6% 34% 33% 6%	455
June	1st to 10th	Night	23% 5% 29% 34% 8%	420
	11th to 20th	Night	18% 6% 24% 39% 12%	410
	21st to end	Night	23% 8% 28% 32% 9% 1	400
July	1st to 10th	Night	18% 5% 30% 34% 14% 1	390
	11th to 20th	Night	15% 5% 26% 41% 13%	388
	21st to end	Night	17% 5% 21% 39% 17% 1	438
August	1st to 10th	Night	16% 3 20% 45% 16%	573
	11th to 20th	Night	16% 2 20% 43% 18% 1	592
	21st to end	Night	14% 4 28% 38% 15% 2	660
September	1st to 10th	Night	16% 4 31% 35% 13%	715
	11th to 20th	Night	17% 8% 22% 36% 15% 2	800
	21st to end	Night	20% 7% 27% 32% 13% 1	800
October	1st to 10th	Night	22% 6% 29% 32% 11% 1	800
	11th to 20th	Night	23% 10% 32% 26% 10%	800
	21st to end	Night	25% 11% 34% 25% 5%	880
November	1st to 10th	Night	25% 13% 32% 25% 5%	823
	11th to 20th	Night	24% 16% 30% 23% 6% 1	950
	21st to end	Night	27% 11% 31% 25% 5%	950
December	1st to 10th	Night	27% 11% 34% 23% 4 1	950
	11th to 20th	Night	24% 14% 35% 23% 5%	950
	21st to end	Night	25% 15% 31% 22% 5% 1	1045

Page generated at 2026-06-13 02:31:41. Version ac07

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