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 2025-02-21.

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%	108066
	Night	17% 11% 4 8% 5% 5% 5% 4 5% 6% 31%	110575
Transparency	Day	51% 7% 13% 19% 9% 1	111583
	Night	52% 6% 13% 19% 9% 1	115223
Seeing	Day	22% 12% 29% 24% 11% 2	16266
	Night	22% 10% 31% 28% 8% 1	24473

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	13% 19% 8% 13% 6% 6% 4 3 4 5% 19%	3184
	11th to 20th	Day	11% 13% 6% 15% 6% 5% 5% 4 6% 5% 24%	3570
	21st to end	Day	6% 9% 4 12% 7% 7% 7% 5% 6% 7% 31%	3960
February	1st to 10th	Day	11% 14% 5% 7% 7% 8% 5% 5% 7% 5% 26%	1790
	11th to 20th	Day	15% 13% 4 11% 6% 6% 5% 3 6% 5% 26%	1773
	21st to end	Day	12% 10% 4 9% 6% 6% 6% 5% 5% 6% 30%	1570
March	1st to 10th	Day	19% 13% 4 8% 6% 5% 4 3 5% 6% 27%	3171
	11th to 20th	Day	18% 17% 6% 11% 6% 5% 4 3 4 5% 20%	3480
	21st to end	Day	22% 13% 4 9% 5% 4 4 3 4 5% 27%	3816
April	1st to 10th	Day	19% 12% 3 9% 6% 5% 5% 4 5% 4 27%	2271
	11th to 20th	Day	19% 9% 2 7% 6% 5% 5% 3 5% 6% 33%	2442
	21st to end	Day	23% 11% 3 6% 4 4 3 3 5% 6% 32%	2470
May	1st to 10th	Day	17% 9% 3 8% 6% 6% 6% 4 5% 7% 30%	4106
	11th to 20th	Day	21% 9% 3 6% 5% 4 4 4 6% 7% 31%	4287
	21st to end	Day	16% 7% 3 8% 6% 6% 6% 4 7% 7% 31%	5185
June	1st to 10th	Day	22% 9% 2 6% 6% 5% 5% 4 6% 7% 27%	2850
	11th to 20th	Day	19% 6% 3 7% 5% 5% 4 3 6% 7% 33%	2850
	21st to end	Day	23% 9% 3 7% 5% 6% 6% 5% 5% 6% 25%	2850
July	1st to 10th	Day	14% 7% 2 8% 6% 5% 6% 6% 7% 8% 31%	4760
	11th to 20th	Day	15% 5% 2 7% 6% 5% 5% 5% 7% 8% 35%	4650
	21st to end	Day	13% 6% 2 6% 5% 5% 4 5% 7% 8% 38%	4814
August	1st to 10th	Day	17% 6% 3 7% 5% 6% 6% 5% 7% 8% 32%	4110
	11th to 20th	Day	15% 7% 3 8% 6% 6% 6% 5% 7% 8% 30%	4045
	21st to end	Day	16% 6% 2 7% 5% 4 5% 4 6% 8% 37%	4532
September	1st to 10th	Day	15% 7% 2 6% 4 4 4 3 5% 8% 43%	2253
	11th to 20th	Day	16% 6% 2 4 4 4 4 3 4 6% 48%	2090
	21st to end	Day	18% 6% 2 6% 4 4 4 4 6% 7% 40%	2090
October	1st to 10th	Day	17% 8% 3 6% 5% 5% 4 3 5% 6% 38%	1990
	11th to 20th	Day	21% 9% 3 8% 4 4 4 3 5% 7% 33%	1886
	21st to end	Day	23% 10% 4 7% 4 4 4 4 5% 7% 27%	1881
November	1st to 10th	Day	19% 10% 4 8% 4 6% 5% 4 5% 5% 31%	1756
	11th to 20th	Day	19% 12% 4 8% 5% 5% 5% 4 5% 6% 28%	1600
	21st to end	Day	20% 13% 3 10% 4 5% 4 4 5% 7% 26%	1600
December	1st to 10th	Day	18% 13% 4 9% 5% 4 4 4 5% 6% 28%	2290
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 6% 31%	2618
	21st to end	Day	17% 15% 5% 11% 5% 5% 4 3 5% 6% 25%	3476
January	1st to 10th	Night	13% 17% 7% 13% 8% 6% 5% 4 5% 5% 17%	6762
	11th to 20th	Night	12% 13% 7% 12% 7% 6% 5% 4 5% 6% 22%	6315
	21st to end	Night	7% 10% 4 9% 6% 5% 6% 5% 7% 7% 34%	6996
February	1st to 10th	Night	12% 14% 5% 9% 7% 6% 5% 4 5% 6% 28%	2610
	11th to 20th	Night	13% 16% 5% 10% 8% 7% 5% 4 4 5% 25%	2512
	21st to end	Night	13% 14% 2 9% 7% 5% 5% 4 5% 5% 33%	1885
March	1st to 10th	Night	19% 11% 4 8% 5% 5% 7% 4 4 6% 27%	3669
	11th to 20th	Night	16% 17% 6% 10% 5% 5% 5% 3 4 6% 22%	3479
	21st to end	Night	27% 12% 3 7% 4 3 3 3 4 7% 27%	3816
April	1st to 10th	Night	22% 13% 2 7% 5% 4 3 3 4 4 32%	1905
	11th to 20th	Night	21% 8% 3 8% 4 4 4 4 5% 6% 34%	1688
	21st to end	Night	24% 11% 3 6% 4 5% 4 2 5% 4 32%	1710
May	1st to 10th	Night	19% 10% 3 6% 4 4 4 4 5% 7% 33%	2834
	11th to 20th	Night	20% 8% 2 8% 5% 5% 5% 4 5% 6% 31%	2626
	21st to end	Night	15% 6% 2 6% 4 3 5% 3 7% 8% 39%	2401
June	1st to 10th	Night	25% 7% 2 6% 4 5% 5% 4 5% 6% 31%	1330
	11th to 20th	Night	17% 5% 2 5% 4 4 5% 5% 7% 8% 37%	1330
	21st to end	Night	22% 10% 3 7% 5% 4 4 3 5% 6% 30%	1330
July	1st to 10th	Night	12% 6% 2 7% 5% 5% 5% 4 7% 8% 39%	2210
	11th to 20th	Night	18% 6% 2 6% 4 4 4 4 6% 7% 38%	2300
	21st to end	Night	12% 6% 3 6% 4 5% 5% 4 6% 7% 41%	2739
August	1st to 10th	Night	17% 7% 3 8% 7% 5% 5% 4 6% 8% 31%	2789
	11th to 20th	Night	12% 7% 2 8% 6% 5% 5% 5% 7% 9% 34%	2782
	21st to end	Night	18% 5% 2 6% 4 4 3 3 4 6% 46%	3124
September	1st to 10th	Night	14% 6% 2 6% 4 5% 4 2 5% 8% 45%	1923
	11th to 20th	Night	14% 6% 2 6% 4 3 3 3 4 6% 47%	2090
	21st to end	Night	17% 5% 2 5% 4 3 4 3 5% 6% 45%	2090
October	1st to 10th	Night	19% 7% 3 6% 3 3 4 3 5% 7% 42%	2190
	11th to 20th	Night	19% 10% 2 7% 4 5% 4 4 5% 5% 36%	2291
	21st to end	Night	22% 10% 3 7% 4 3 4 3 5% 6% 32%	2717
November	1st to 10th	Night	19% 10% 3 6% 4 4 4 4 5% 7% 33%	2542
	11th to 20th	Night	19% 11% 3 8% 4 5% 4 3 5% 6% 31%	2800
	21st to end	Night	20% 11% 3 9% 6% 5% 4 3 5% 7% 27%	2800
December	1st to 10th	Night	16% 12% 5% 10% 7% 5% 6% 5% 6% 5% 24%	4897
	11th to 20th	Night	22% 11% 3 7% 4 4 4 3 5% 6% 31%	5591
	21st to end	Night	18% 12% 4 11% 6% 4 4 3 5% 6% 25%	7502

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	66% 6% 11% 13% 4	3185
	11th to 20th	Day	61% 6% 10% 18% 5%	3600
	21st to end	Day	48% 9% 11% 15% 17% 1	3960
February	1st to 10th	Day	57% 6% 12% 15% 9% 1	1790
	11th to 20th	Day	59% 6% 12% 15% 7% 1	1781
	21st to end	Day	50% 8% 13% 19% 9% 2	1570
March	1st to 10th	Day	57% 7% 11% 12% 11% 3	3175
	11th to 20th	Day	65% 7% 11% 10% 6% 1	3480
	21st to end	Day	59% 5% 8% 17% 10% 2	3816
April	1st to 10th	Day	57% 5% 12% 15% 8% 2	2271
	11th to 20th	Day	48% 6% 13% 19% 12% 2	2442
	21st to end	Day	54% 5% 9% 17% 11% 3	2470
May	1st to 10th	Day	50% 8% 13% 21% 8% 1	4120
	11th to 20th	Day	50% 7% 17% 18% 7% 1	4291
	21st to end	Day	48% 9% 13% 18% 12% 1	5185
June	1st to 10th	Day	54% 7% 14% 15% 10% 1	2850
	11th to 20th	Day	49% 6% 14% 18% 11% 2	2850
	21st to end	Day	58% 8% 12% 15% 7%	2850
July	1st to 10th	Day	47% 8% 18% 19% 8%	4685
	11th to 20th	Day	46% 7% 16% 27% 5%	4569
	21st to end	Day	43% 8% 16% 25% 8%	4661
August	1st to 10th	Day	48% 8% 17% 21% 6%	4096
	11th to 20th	Day	49% 9% 16% 21% 4	4084
	21st to end	Day	43% 7% 15% 24% 11%	4532
September	1st to 10th	Day	40% 7% 16% 25% 12%	2253
	11th to 20th	Day	39% 5% 13% 28% 14% 1	2090
	21st to end	Day	42% 7% 12% 26% 12%	2090
October	1st to 10th	Day	50% 5% 13% 27% 5%	3302
	11th to 20th	Day	48% 4 12% 28% 8%	3114
	21st to end	Day	47% 5% 15% 20% 12%	3081
November	1st to 10th	Day	54% 6% 13% 20% 7% 1	1756
	11th to 20th	Day	55% 9% 11% 15% 9% 1	1600
	21st to end	Day	59% 7% 16% 15% 3	1600
December	1st to 10th	Day	57% 6% 17% 11% 9%	2290
	11th to 20th	Day	53% 6% 11% 19% 9% 3	2618
	21st to end	Day	60% 5% 12% 11% 10% 1	3476
January	1st to 10th	Night	68% 6% 13% 10% 3	6762
	11th to 20th	Night	63% 6% 11% 15% 5%	6360
	21st to end	Night	46% 6% 10% 20% 17% 1	6996
February	1st to 10th	Night	56% 5% 11% 16% 10% 1	2610
	11th to 20th	Night	62% 6% 10% 14% 8% 1	2515
	21st to end	Night	53% 6% 10% 17% 12% 2	1885
March	1st to 10th	Night	57% 6% 11% 19% 7% 1	3678
	11th to 20th	Night	63% 6% 11% 12% 7%	3480
	21st to end	Night	59% 3 7% 19% 11% 2	3816
April	1st to 10th	Night	56% 4 9% 17% 11% 3	1905
	11th to 20th	Night	49% 6% 12% 18% 15% 1	1688
	21st to end	Night	54% 5% 8% 16% 14% 2	1710
May	1st to 10th	Night	47% 8% 15% 20% 9% 1	2840
	11th to 20th	Night	51% 8% 13% 21% 7% 1	2627
	21st to end	Night	40% 10% 14% 23% 13%	2402
June	1st to 10th	Night	52% 5% 14% 20% 9% 1	1330
	11th to 20th	Night	41% 9% 15% 21% 12% 1	1330
	21st to end	Night	56% 6% 12% 16% 9% 1	1330
July	1st to 10th	Night	42% 6% 22% 21% 9%	2175
	11th to 20th	Night	44% 8% 17% 25% 6%	2258
	21st to end	Night	40% 9% 18% 25% 7%	2651
August	1st to 10th	Night	52% 7% 14% 22% 5%	2779
	11th to 20th	Night	45% 10% 22% 17% 7%	2809
	21st to end	Night	41% 6% 14% 24% 14% 1	3124
September	1st to 10th	Night	39% 6% 14% 28% 12% 1	1923
	11th to 20th	Night	38% 6% 14% 28% 14%	2090
	21st to end	Night	40% 7% 13% 25% 14% 1	2090
October	1st to 10th	Night	48% 5% 12% 26% 8%	3658
	11th to 20th	Night	47% 5% 12% 29% 8%	3802
	21st to end	Night	43% 6% 19% 21% 12%	4467
November	1st to 10th	Night	51% 6% 14% 20% 8%	2542
	11th to 20th	Night	53% 7% 13% 16% 10% 1	2800
	21st to end	Night	58% 8% 14% 14% 6% 1	2800
December	1st to 10th	Night	61% 5% 12% 18% 4	4897
	11th to 20th	Night	53% 5% 11% 20% 11% 1	5592
	21st to end	Night	59% 5% 10% 16% 9% 1	7502

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	21% 19% 27% 26% 8%	200
	11th to 20th	Day	24% 19% 28% 19% 10% 1	200
	21st to end	Day	14% 14% 38% 21% 9% 4	220
February	1st to 10th	Day	21% 14% 29% 26% 8% 1	390
	11th to 20th	Day	17% 14% 39% 23% 5% 1	406
	21st to end	Day	18% 16% 34% 25% 7%	382
March	1st to 10th	Day	25% 13% 30% 25% 7%	460
	11th to 20th	Day	20% 13% 31% 26% 10% 1	460
	21st to end	Day	22% 15% 26% 28% 8% 2	506
April	1st to 10th	Day	27% 16% 26% 21% 10% 1	460
	11th to 20th	Day	22% 12% 30% 23% 11% 2	452
	21st to end	Day	28% 13% 24% 24% 10% 2	460
May	1st to 10th	Day	26% 12% 27% 23% 11% 1	463
	11th to 20th	Day	27% 13% 25% 21% 10% 3	565
	21st to end	Day	21% 15% 32% 23% 8% 1	735
June	1st to 10th	Day	24% 13% 28% 24% 8% 2	680
	11th to 20th	Day	21% 11% 27% 25% 14% 2	680
	21st to end	Day	24% 7% 31% 25% 10% 2	680
July	1st to 10th	Day	17% 7% 31% 28% 15% 2	670
	11th to 20th	Day	17% 7% 27% 32% 15% 2	610
	21st to end	Day	17% 5% 30% 32% 15% 2	532
August	1st to 10th	Day	18% 8% 27% 28% 15% 5%	486
	11th to 20th	Day	16% 9% 21% 30% 21% 3	479
	21st to end	Day	19% 11% 21% 27% 17% 5%	539
September	1st to 10th	Day	16% 10% 29% 27% 15% 4	490
	11th to 20th	Day	21% 9% 23% 26% 13% 8%	490
	21st to end	Day	20% 9% 28% 22% 13% 7%	490
October	1st to 10th	Day	20% 11% 27% 21% 16% 5%	437
	11th to 20th	Day	25% 16% 27% 19% 10% 3	390
	21st to end	Day	29% 14% 29% 21% 7% 1	429
November	1st to 10th	Day	28% 14% 30% 19% 7% 1	395
	11th to 20th	Day	28% 14% 29% 20% 8% 1	400
	21st to end	Day	27% 13% 31% 23% 6%	400
December	1st to 10th	Day	22% 13% 31% 18% 13% 2	210
	11th to 20th	Day	22% 19% 38% 16% 5% 2	200
	21st to end	Day	23% 19% 29% 19% 10% 1	220
January	1st to 10th	Night	22% 12% 36% 26% 4	890
	11th to 20th	Night	24% 15% 31% 24% 6%	800
	21st to end	Night	15% 11% 39% 28% 7%	880
February	1st to 10th	Night	18% 12% 41% 23% 5% 1	800
	11th to 20th	Night	21% 14% 37% 23% 4 1	783
	21st to end	Night	20% 11% 36% 27% 5%	629
March	1st to 10th	Night	20% 10% 37% 29% 3	760
	11th to 20th	Night	23% 11% 33% 25% 7% 1	760
	21st to end	Night	22% 9% 37% 26% 6% 1	836
April	1st to 10th	Night	29% 11% 30% 25% 5%	725
	11th to 20th	Night	25% 10% 31% 25% 8% 1	564
	21st to end	Night	30% 10% 28% 24% 8% 1	570
May	1st to 10th	Night	26% 7% 31% 28% 6% 1	570
	11th to 20th	Night	25% 9% 32% 27% 7% 1	540
	21st to end	Night	22% 6% 35% 32% 6%	411
June	1st to 10th	Night	24% 6% 27% 34% 9% 1	380
	11th to 20th	Night	18% 5% 23% 40% 13%	380
	21st to end	Night	23% 8% 28% 32% 9% 1	380
July	1st to 10th	Night	18% 5% 30% 34% 14% 1	370
	11th to 20th	Night	16% 5% 25% 40% 14%	368
	21st to end	Night	18% 5% 21% 39% 18% 1	416
August	1st to 10th	Night	17% 3 20% 44% 15%	544
	11th to 20th	Night	17% 2 20% 43% 17% 1	562
	21st to end	Night	14% 4 27% 37% 15% 2	627
September	1st to 10th	Night	17% 4 32% 34% 13%	679
	11th to 20th	Night	18% 8% 22% 36% 15% 1	760
	21st to end	Night	20% 7% 27% 32% 13% 1	760
October	1st to 10th	Night	22% 6% 29% 31% 11% 1	760
	11th to 20th	Night	23% 10% 33% 25% 9%	760
	21st to end	Night	26% 11% 34% 24% 5%	836
November	1st to 10th	Night	25% 12% 32% 25% 6%	783
	11th to 20th	Night	24% 16% 30% 23% 6% 1	900
	21st to end	Night	28% 12% 31% 24% 5%	900
December	1st to 10th	Night	28% 10% 33% 23% 4 2	900
	11th to 20th	Night	24% 14% 34% 23% 5%	900
	21st to end	Night	26% 15% 31% 22% 5% 1	990

Page generated at 2025-02-18 03:26:30. Version ac07

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