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 2024-01-31.

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	18% 9% 4 7% 6% 4 5% 5% 5% 7% 31%	74756
	Night	18% 10% 4 7% 6% 3 5% 5% 5% 6% 32%	75382
Transparency	Day	52% 7% 13% 18% 9% 1	74450
	Night	52% 7% 12% 19% 9% 1	75223
Seeing	Day	22% 12% 28% 25% 11% 2	14878
	Night	22% 10% 31% 28% 8% 1	23090

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	14% 15% 7% 11% 7% 4 5% 4 5% 6% 23%	1341
	11th to 20th	Day	16% 14% 6% 10% 6% 3 4 4 5% 6% 25%	1520
	21st to end	Day	9% 10% 4 9% 6% 4 6% 6% 6% 8% 31%	1664
February	1st to 10th	Day	12% 14% 5% 6% 7% 6% 6% 6% 7% 6% 25%	1611
	11th to 20th	Day	16% 12% 5% 9% 6% 4 6% 5% 6% 6% 26%	1591
	21st to end	Day	12% 9% 4 8% 7% 4 7% 6% 5% 7% 30%	1480
March	1st to 10th	Day	16% 11% 4 7% 8% 5% 5% 5% 5% 7% 27%	1824
	11th to 20th	Day	16% 10% 6% 7% 7% 4 6% 4 5% 7% 28%	1980
	21st to end	Day	15% 12% 5% 10% 6% 3 4 4 4 6% 32%	2178
April	1st to 10th	Day	20% 11% 4 8% 7% 4 5% 5% 6% 5% 25%	2151
	11th to 20th	Day	19% 8% 3 5% 7% 3 5% 4 5% 7% 34%	2312
	21st to end	Day	25% 11% 4 5% 5% 3 4 4 4 6% 30%	2340
May	1st to 10th	Day	22% 9% 3 7% 6% 3 5% 5% 4 6% 30%	2340
	11th to 20th	Day	24% 7% 3 5% 7% 3 4 4 5% 6% 34%	2409
	21st to end	Day	19% 7% 3 6% 7% 4 6% 5% 5% 8% 32%	2919
June	1st to 10th	Day	22% 9% 2 6% 6% 4 5% 6% 6% 7% 27%	2700
	11th to 20th	Day	21% 6% 3 6% 6% 4 5% 4 6% 8% 33%	2700
	21st to end	Day	23% 8% 3 7% 6% 4 7% 6% 5% 7% 25%	2700
July	1st to 10th	Day	15% 6% 2 7% 6% 4 6% 6% 6% 9% 32%	2700
	11th to 20th	Day	14% 6% 3 7% 7% 4 5% 6% 7% 9% 33%	2646
	21st to end	Day	15% 7% 3 6% 5% 4 5% 6% 8% 9% 31%	2744
August	1st to 10th	Day	17% 5% 3 5% 6% 3 6% 5% 6% 9% 33%	2332
	11th to 20th	Day	13% 6% 3 7% 7% 4 6% 5% 7% 8% 34%	2304
	21st to end	Day	14% 7% 3 6% 6% 3 4 6% 6% 8% 37%	2574
September	1st to 10th	Day	15% 6% 3 5% 5% 2 4 4 5% 9% 42%	2135
	11th to 20th	Day	17% 6% 2 4 4 3 3 4 4 6% 47%	1980
	21st to end	Day	18% 5% 2 5% 5% 3 4 5% 5% 7% 41%	1980
October	1st to 10th	Day	16% 8% 4 6% 5% 4 4 4 4 7% 38%	1886
	11th to 20th	Day	21% 9% 3 7% 5% 3 5% 4 5% 6% 33%	1787
	21st to end	Day	24% 10% 4 6% 5% 4 4 5% 5% 7% 25%	1782
November	1st to 10th	Day	19% 9% 4 6% 6% 4 4 5% 5% 5% 32%	1667
	11th to 20th	Day	19% 9% 4 7% 6% 4 6% 5% 5% 6% 28%	1520
	21st to end	Day	19% 11% 4 9% 5% 3 5% 5% 5% 7% 27%	1520
December	1st to 10th	Day	22% 12% 5% 8% 6% 3 4 4 4 5% 25%	1340
	11th to 20th	Day	20% 11% 5% 9% 7% 3 6% 4 5% 5% 26%	1668
	21st to end	Day	20% 13% 4 10% 7% 4 4 4 3 4 27%	2431
January	1st to 10th	Night	15% 13% 6% 11% 7% 5% 6% 6% 5% 6% 21%	2819
	11th to 20th	Night	16% 14% 6% 8% 7% 5% 6% 5% 5% 5% 23%	2660
	21st to end	Night	10% 11% 4 8% 7% 4 6% 6% 7% 7% 30%	2919
February	1st to 10th	Night	13% 13% 5% 7% 8% 5% 6% 5% 5% 7% 27%	2349
	11th to 20th	Night	13% 15% 5% 8% 9% 5% 6% 5% 4 5% 24%	2255
	21st to end	Night	13% 13% 3 8% 7% 4 5% 5% 4 5% 33%	1776
March	1st to 10th	Night	15% 11% 5% 8% 7% 3 6% 5% 5% 7% 29%	2123
	11th to 20th	Night	16% 10% 5% 8% 6% 4 6% 4 5% 6% 30%	1979
	21st to end	Night	16% 11% 4 10% 6% 3 4 4 5% 5% 32%	2178
April	1st to 10th	Night	23% 12% 3 6% 6% 3 4 3 4 4 31%	1805
	11th to 20th	Night	21% 7% 3 6% 6% 3 4 4 5% 7% 35%	1598
	21st to end	Night	25% 11% 3 5% 5% 3 5% 3 5% 4 31%	1620
May	1st to 10th	Night	21% 10% 3 6% 5% 3 4 5% 5% 7% 30%	1620
	11th to 20th	Night	22% 8% 2 7% 5% 3 5% 4 4 6% 34%	1499
	21st to end	Night	19% 7% 3 6% 5% 3 4 4 5% 7% 36%	1356
June	1st to 10th	Night	25% 6% 2 6% 5% 3 6% 5% 4 7% 31%	1260
	11th to 20th	Night	18% 5% 2 5% 4 3 6% 6% 6% 8% 38%	1260
	21st to end	Night	22% 8% 4 6% 6% 4 4 4 5% 6% 32%	1260
July	1st to 10th	Night	16% 6% 3 6% 7% 3 5% 5% 5% 8% 36%	1260
	11th to 20th	Night	14% 6% 3 5% 5% 3 5% 5% 7% 8% 39%	1311
	21st to end	Night	17% 7% 3 6% 5% 4 5% 5% 5% 7% 36%	1574
August	1st to 10th	Night	14% 6% 3 5% 7% 3 4 4 6% 9% 39%	1589
	11th to 20th	Night	13% 7% 2 6% 7% 4 5% 5% 7% 9% 36%	1596
	21st to end	Night	12% 4 2 5% 5% 3 4 4 5% 8% 48%	1782
September	1st to 10th	Night	14% 6% 2 5% 5% 3 5% 3 5% 8% 45%	1821
	11th to 20th	Night	15% 6% 2 5% 5% 2 4 4 4 6% 46%	1980
	21st to end	Night	18% 4 2 4 5% 2 4 4 5% 6% 46%	1980
October	1st to 10th	Night	19% 6% 3 5% 4 3 4 3 4 7% 43%	2074
	11th to 20th	Night	19% 10% 3 5% 5% 4 3 5% 5% 6% 35%	2170
	21st to end	Night	23% 9% 3 6% 5% 3 4 4 5% 6% 32%	2574
November	1st to 10th	Night	20% 9% 4 5% 5% 3 5% 5% 5% 7% 33%	2411
	11th to 20th	Night	19% 9% 4 7% 6% 3 6% 4 5% 7% 31%	2660
	21st to end	Night	19% 10% 4 8% 7% 3 6% 4 5% 7% 28%	2660
December	1st to 10th	Night	23% 12% 5% 8% 7% 3 5% 4 4 5% 24%	2837
	11th to 20th	Night	24% 10% 4 8% 6% 3 5% 5% 5% 6% 26%	3531
	21st to end	Night	21% 13% 4 7% 6% 3 5% 5% 5% 5% 26%	5236

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	61% 8% 10% 14% 6%	1342
	11th to 20th	Day	62% 6% 9% 16% 7% 1	1520
	21st to end	Day	48% 8% 14% 18% 11% 1	1664
February	1st to 10th	Day	58% 6% 12% 14% 9% 1	1611
	11th to 20th	Day	59% 7% 12% 14% 7% 1	1599
	21st to end	Day	51% 8% 13% 18% 9% 2	1480
March	1st to 10th	Day	55% 6% 12% 14% 11% 1	1828
	11th to 20th	Day	55% 6% 13% 14% 10% 2	1980
	21st to end	Day	55% 5% 9% 20% 9% 2	2178
April	1st to 10th	Day	58% 5% 12% 14% 8% 2	2151
	11th to 20th	Day	49% 6% 13% 18% 12% 2	2312
	21st to end	Day	55% 5% 9% 17% 11% 4	2340
May	1st to 10th	Day	54% 5% 10% 17% 12% 1	2340
	11th to 20th	Day	52% 5% 11% 19% 11% 1	2413
	21st to end	Day	50% 7% 13% 19% 10% 1	2919
June	1st to 10th	Day	55% 7% 14% 14% 10% 1	2700
	11th to 20th	Day	49% 6% 13% 18% 12% 1	2700
	21st to end	Day	58% 8% 12% 14% 7%	2700
July	1st to 10th	Day	45% 9% 18% 20% 7% 1	2625
	11th to 20th	Day	46% 8% 14% 23% 8%	2565
	21st to end	Day	47% 9% 15% 21% 7% 1	2591
August	1st to 10th	Day	46% 10% 18% 20% 5%	2318
	11th to 20th	Day	46% 10% 15% 23% 6%	2304
	21st to end	Day	43% 8% 15% 26% 8%	2574
September	1st to 10th	Day	40% 7% 16% 24% 12%	2135
	11th to 20th	Day	40% 5% 13% 27% 15% 1	1980
	21st to end	Day	41% 7% 13% 26% 13%	1980
October	1st to 10th	Day	46% 5% 12% 27% 9%	1886
	11th to 20th	Day	53% 6% 15% 20% 6%	1787
	21st to end	Day	58% 7% 13% 14% 8%	1782
November	1st to 10th	Day	53% 6% 13% 20% 7% 1	1667
	11th to 20th	Day	54% 9% 11% 15% 9% 1	1520
	21st to end	Day	57% 7% 17% 16% 3	1520
December	1st to 10th	Day	62% 6% 13% 13% 6%	1340
	11th to 20th	Day	59% 6% 10% 15% 9%	1668
	21st to end	Day	61% 6% 12% 14% 6% 1	2431
January	1st to 10th	Night	63% 7% 12% 12% 6% 1	2819
	11th to 20th	Night	63% 7% 10% 14% 6% 1	2660
	21st to end	Night	50% 7% 12% 19% 10% 1	2919
February	1st to 10th	Night	57% 6% 12% 16% 9% 1	2349
	11th to 20th	Night	62% 6% 9% 14% 8% 1	2258
	21st to end	Night	54% 6% 9% 17% 12% 1	1776
March	1st to 10th	Night	54% 5% 10% 20% 9% 2	2132
	11th to 20th	Night	54% 6% 11% 15% 13% 1	1980
	21st to end	Night	54% 5% 10% 18% 11% 2	2178
April	1st to 10th	Night	57% 4 9% 16% 11% 3	1805
	11th to 20th	Night	48% 6% 12% 18% 15% 2	1598
	21st to end	Night	56% 5% 8% 16% 14% 2	1620
May	1st to 10th	Night	52% 7% 8% 17% 14% 2	1620
	11th to 20th	Night	51% 6% 10% 20% 11% 1	1500
	21st to end	Night	47% 8% 11% 19% 13% 1	1357
June	1st to 10th	Night	53% 5% 13% 20% 8% 1	1260
	11th to 20th	Night	42% 10% 14% 21% 13% 1	1260
	21st to end	Night	54% 6% 12% 17% 9% 1	1260
July	1st to 10th	Night	45% 7% 19% 22% 7%	1225
	11th to 20th	Night	41% 10% 17% 24% 9%	1269
	21st to end	Night	46% 8% 15% 22% 9%	1486
August	1st to 10th	Night	42% 9% 18% 26% 6%	1579
	11th to 20th	Night	43% 10% 20% 21% 5%	1596
	21st to end	Night	34% 8% 15% 31% 11%	1782
September	1st to 10th	Night	38% 6% 14% 27% 12% 1	1821
	11th to 20th	Night	39% 6% 14% 27% 14%	1980
	21st to end	Night	39% 7% 13% 26% 15% 1	1980
October	1st to 10th	Night	42% 5% 13% 27% 12%	2074
	11th to 20th	Night	50% 7% 12% 22% 8%	2170
	21st to end	Night	53% 7% 13% 18% 8%	2574
November	1st to 10th	Night	51% 6% 14% 20% 8%	2411
	11th to 20th	Night	52% 7% 14% 16% 10% 1	2660
	21st to end	Night	56% 9% 14% 14% 6% 1	2660
December	1st to 10th	Night	63% 5% 11% 17% 4	2837
	11th to 20th	Night	59% 6% 12% 15% 8%	3532
	21st to end	Night	58% 6% 12% 15% 8% 1	5236

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% 18% 24% 28% 9%	180
	11th to 20th	Day	24% 18% 31% 18% 7% 1	180
	21st to end	Day	15% 14% 34% 23% 9% 5%	196
February	1st to 10th	Day	24% 14% 29% 26% 7%	331
	11th to 20th	Day	18% 14% 40% 22% 5% 1	344
	21st to end	Day	17% 16% 35% 25% 7%	346
March	1st to 10th	Day	25% 13% 31% 24% 7%	420
	11th to 20th	Day	19% 13% 32% 25% 10% 1	420
	21st to end	Day	20% 15% 27% 27% 9% 2	462
April	1st to 10th	Day	27% 17% 25% 20% 10% 1	420
	11th to 20th	Day	23% 10% 30% 24% 11% 2	412
	21st to end	Day	29% 11% 23% 24% 10% 2	420
May	1st to 10th	Day	27% 12% 28% 22% 10% 1	423
	11th to 20th	Day	28% 14% 26% 21% 9% 2	520
	21st to end	Day	22% 15% 30% 24% 8% 1	680
June	1st to 10th	Day	25% 13% 29% 24% 8% 2	630
	11th to 20th	Day	22% 11% 26% 25% 13% 2	630
	21st to end	Day	24% 6% 31% 25% 11% 3	630
July	1st to 10th	Day	17% 7% 31% 29% 15% 2	620
	11th to 20th	Day	17% 6% 28% 32% 16% 2	564
	21st to end	Day	16% 5% 30% 32% 15% 2	488
August	1st to 10th	Day	18% 8% 25% 30% 15% 4	446
	11th to 20th	Day	16% 9% 21% 30% 21% 4	439
	21st to end	Day	19% 12% 20% 27% 18% 4	495
September	1st to 10th	Day	16% 10% 28% 25% 16% 4	450
	11th to 20th	Day	22% 10% 24% 24% 12% 7%	450
	21st to end	Day	20% 10% 29% 22% 12% 6%	450
October	1st to 10th	Day	19% 11% 28% 22% 16% 4	403
	11th to 20th	Day	26% 16% 27% 19% 9% 4	360
	21st to end	Day	30% 12% 28% 21% 7% 1	396
November	1st to 10th	Day	27% 15% 30% 20% 8% 1	365
	11th to 20th	Day	25% 14% 30% 21% 8% 1	370
	21st to end	Day	25% 14% 30% 25% 6%	370
December	1st to 10th	Day	22% 14% 30% 18% 13% 3	190
	11th to 20th	Day	22% 18% 39% 16% 4 1	180
	21st to end	Day	24% 20% 30% 19% 7% 1	198
January	1st to 10th	Night	21% 11% 36% 27% 4	841
	11th to 20th	Night	25% 15% 32% 23% 5%	760
	21st to end	Night	16% 10% 38% 28% 8%	835
February	1st to 10th	Night	19% 12% 41% 23% 5%	720
	11th to 20th	Night	22% 15% 36% 23% 5%	703
	21st to end	Night	21% 10% 36% 27% 6% 1	592
March	1st to 10th	Night	20% 10% 37% 30% 3	720
	11th to 20th	Night	23% 11% 33% 25% 7% 1	720
	21st to end	Night	20% 9% 37% 27% 6% 1	792
April	1st to 10th	Night	29% 11% 30% 24% 5%	687
	11th to 20th	Night	25% 10% 31% 25% 8% 1	534
	21st to end	Night	31% 9% 27% 24% 9% 1	540
May	1st to 10th	Night	26% 7% 31% 29% 6% 1	540
	11th to 20th	Night	25% 9% 32% 27% 6% 1	512
	21st to end	Night	22% 6% 34% 31% 6%	389
June	1st to 10th	Night	25% 6% 27% 34% 8% 1	360
	11th to 20th	Night	19% 5% 23% 40% 13%	360
	21st to end	Night	22% 8% 28% 32% 10% 1	360
July	1st to 10th	Night	18% 4 29% 34% 14% 1	350
	11th to 20th	Night	15% 5% 26% 40% 14%	348
	21st to end	Night	19% 5% 20% 38% 18% 1	394
August	1st to 10th	Night	16% 3 21% 44% 15%	515
	11th to 20th	Night	17% 2 20% 43% 17% 1	532
	21st to end	Night	13% 4 28% 38% 15% 2	594
September	1st to 10th	Night	16% 4 32% 34% 14%	643
	11th to 20th	Night	19% 8% 23% 36% 13% 1	720
	21st to end	Night	20% 7% 28% 32% 12% 1	720
October	1st to 10th	Night	22% 6% 29% 32% 11% 1	720
	11th to 20th	Night	23% 10% 33% 24% 10%	720
	21st to end	Night	27% 11% 32% 24% 5%	792
November	1st to 10th	Night	25% 12% 32% 25% 6%	742
	11th to 20th	Night	23% 17% 30% 23% 6% 1	850
	21st to end	Night	26% 12% 32% 25% 5%	850
December	1st to 10th	Night	29% 11% 34% 22% 4 2	850
	11th to 20th	Night	24% 14% 34% 23% 5%	850
	21st to end	Night	26% 16% 31% 22% 5% 1	935

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