John Paul II Catholic High School
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the John Paul II Catholic High School clear sky chart from 2005-11-06 to 2025-09-19.

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	14% 6% 2 5% 4 4 4 3 5% 7% 45%	126263
	Night	16% 6% 2 5% 3 3 3 3 5% 7% 48%	123095
Transparency	Day	37% 5% 10% 21% 18% 10%	130055
	Night	36% 4 11% 19% 18% 12%	127366
Seeing	Day	14% 7% 21% 29% 22% 6%	15962
	Night	17% 6% 24% 35% 16% 1	25821

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	19% 8% 2 4 2 3 3 2 3 5% 48%	4077
	11th to 20th	Day	17% 5% 2 4 2 2 2 2 5% 5% 53%	4080
	21st to end	Day	29% 6% 2 4 2 2 2 2 4 6% 41%	4877
February	1st to 10th	Day	21% 7% 2 6% 3 2 3 3 3 5% 45%	2000
	11th to 20th	Day	20% 8% 2 5% 3 4 2 3 4 6% 43%	1949
	21st to end	Day	20% 6% 2 4 2 2 3 2 4 5% 47%	1650
March	1st to 10th	Day	15% 6% 2 5% 3 3 3 3 4 6% 52%	4884
	11th to 20th	Day	17% 7% 2 6% 4 3 3 2 3 4 50%	4980
	21st to end	Day	21% 8% 2 5% 3 2 2 3 3 6% 44%	5462
April	1st to 10th	Day	16% 7% 3 7% 5% 4 3 3 5% 5% 44%	2200
	11th to 20th	Day	21% 7% 3 5% 3 4 3 2 5% 5% 42%	2176
	21st to end	Day	17% 8% 3 6% 5% 3 4 3 4 6% 42%	2526
May	1st to 10th	Day	23% 8% 2 6% 4 4 4 4 5% 6% 34%	5862
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 6% 7% 47%	5862
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 7% 10% 35%	6434
June	1st to 10th	Day	7% 4 2 5% 4 5% 5% 5% 7% 9% 47%	2600
	11th to 20th	Day	9% 6% 2 6% 5% 6% 5% 4 7% 9% 43%	2600
	21st to end	Day	8% 7% 2 7% 6% 6% 6% 5% 7% 10% 36%	2600
July	1st to 10th	Day	12% 8% 3 8% 5% 6% 5% 4 6% 8% 36%	5900
	11th to 20th	Day	6% 5% 2 7% 5% 5% 6% 6% 8% 10% 39%	5900
	21st to end	Day	8% 6% 2 6% 5% 6% 6% 5% 7% 10% 39%	6422
August	1st to 10th	Day	1 2 1 2 3 3 3 3 6% 9% 66%	4171
	11th to 20th	Day	4 2 1 4 3 3 4 5% 8% 12% 54%	3846
	21st to end	Day	5% 3 2 5% 5% 6% 5% 4 8% 11% 45%	4124
September	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 7% 42%	2200
	11th to 20th	Day	11% 6% 2 7% 4 5% 5% 5% 7% 8% 40%	2178
	21st to end	Day	9% 5% 2 6% 4 4 4 4 6% 7% 50%	2090
October	1st to 10th	Day	6% 5% 1 5% 4 4 4 3 5% 7% 54%	2090
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 4 5% 51%	1976
	21st to end	Day	12% 5% 1 5% 3 2 3 3 3 5% 57%	2090
November	1st to 10th	Day	16% 8% 3 5% 4 4 3 3 5% 6% 43%	1958
	11th to 20th	Day	13% 5% 2 5% 4 3 4 3 5% 5% 49%	1880
	21st to end	Day	18% 7% 3 6% 4 3 4 2 4 5% 44%	1800
December	1st to 10th	Day	30% 8% 2 5% 3 3 2 2 3 5% 36%	2940
	11th to 20th	Day	19% 7% 3 6% 4 4 3 3 4 5% 43%	3391
	21st to end	Day	16% 6% 2 3 2 2 2 2 3 4 57%	4488
January	1st to 10th	Night	21% 6% 2 4 3 2 2 2 3 5% 50%	5888
	11th to 20th	Night	13% 3 1 3 2 2 3 2 4 5% 62%	5900
	21st to end	Night	32% 5% 2 4 2 2 2 3 3 5% 40%	6144
February	1st to 10th	Night	21% 7% 2 4 3 3 3 3 4 5% 47%	2400
	11th to 20th	Night	22% 8% 2 4 3 3 2 2 3 5% 47%	2338
	21st to end	Night	22% 6% 2 4 3 3 3 3 4 5% 45%	1980
March	1st to 10th	Night	19% 7% 2 5% 4 3 3 3 4 4 45%	4972
	11th to 20th	Night	18% 7% 2 5% 3 3 3 2 3 5% 48%	4980
	21st to end	Night	23% 8% 2 4 3 3 3 2 4 5% 42%	5467
April	1st to 10th	Night	16% 7% 2 5% 5% 3 3 3 5% 7% 46%	2200
	11th to 20th	Night	21% 7% 2 5% 4 3 3 3 4 6% 44%	2173
	21st to end	Night	22% 6% 2 5% 4 3 3 2 4 5% 44%	1866
May	1st to 10th	Night	27% 8% 2 6% 4 3 4 3 5% 5% 34%	4053
	11th to 20th	Night	12% 4 2 5% 3 4 4 3 6% 9% 48%	4053
	21st to end	Night	17% 7% 2 6% 4 4 4 3 7% 9% 36%	4443
June	1st to 10th	Night	7% 4 2 4 3 3 4 2 6% 9% 57%	1800
	11th to 20th	Night	6% 4 1 3 4 3 4 4 5% 9% 55%	1800
	21st to end	Night	8% 5% 2 5% 3 4 4 5% 7% 9% 48%	1800
July	1st to 10th	Night	10% 7% 3 7% 4 5% 5% 4 6% 10% 40%	4078
	11th to 20th	Night	6% 4 2 5% 5% 4 5% 5% 8% 12% 44%	4077
	21st to end	Night	10% 6% 2 6% 4 4 4 4 7% 9% 44%	4449
August	1st to 10th	Night	1 1 1 2 2 2 3 3 4 8% 73%	2983
	11th to 20th	Night	3 2 1 3 3 3 4 4 8% 12% 56%	3213
	21st to end	Night	6% 3 2 4 3 3 4 4 7% 10% 54%	3776
September	1st to 10th	Night	9% 6% 2 5% 4 5% 4 3 5% 8% 48%	2200
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 3 6% 8% 46%	2178
	21st to end	Night	9% 5% 2 5% 4 3 3 4 6% 8% 51%	2090
October	1st to 10th	Night	7% 4 1 4 3 4 4 3 5% 7% 59%	2090
	11th to 20th	Night	15% 5% 1 4 4 3 3 2 4 5% 54%	2185
	21st to end	Night	15% 4 1 4 2 2 2 2 3 5% 61%	2508
November	1st to 10th	Night	16% 6% 2 5% 3 3 3 2 4 6% 51%	2340
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 4 6% 54%	2515
	21st to end	Night	19% 5% 2 5% 3 3 3 3 5% 5% 47%	2600
December	1st to 10th	Night	27% 9% 3 5% 4 3 3 3 3 5% 35%	4250
	11th to 20th	Night	23% 7% 2 5% 3 3 2 2 3 4 46%	4816
	21st to end	Night	19% 6% 1 3 2 2 2 2 3 4 55%	6490

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	41% 3 4 18% 23% 11%	4078
	11th to 20th	Day	36% 2 5% 17% 21% 19%	4080
	21st to end	Day	47% 2 3 10% 25% 12%	4877
February	1st to 10th	Day	43% 4 5% 12% 20% 16%	2000
	11th to 20th	Day	42% 4 7% 17% 18% 12%	1959
	21st to end	Day	40% 4 7% 15% 19% 15%	1650
March	1st to 10th	Day	36% 3 5% 20% 15% 21%	4884
	11th to 20th	Day	39% 4 4 8% 17% 28%	4980
	21st to end	Day	42% 4 7% 19% 19% 10%	5464
April	1st to 10th	Day	43% 4 7% 16% 17% 13%	2200
	11th to 20th	Day	44% 4 7% 16% 17% 12%	2176
	21st to end	Day	44% 4 7% 18% 17% 10%	2526
May	1st to 10th	Day	50% 6% 8% 18% 14% 4	5900
	11th to 20th	Day	36% 5% 11% 20% 20% 8%	5866
	21st to end	Day	41% 6% 11% 28% 13% 1	6447
June	1st to 10th	Day	30% 8% 13% 28% 19% 3	2600
	11th to 20th	Day	34% 7% 12% 24% 19% 4	2600
	21st to end	Day	40% 7% 13% 24% 13% 3	2600
July	1st to 10th	Day	47% 5% 16% 27% 5% 1	5836
	11th to 20th	Day	37% 5% 19% 28% 11% 1	5831
	21st to end	Day	37% 5% 17% 25% 13% 3	6240
August	1st to 10th	Day	15% 5% 11% 44% 24% 1	4157
	11th to 20th	Day	21% 6% 24% 35% 11% 2	3882
	21st to end	Day	30% 7% 20% 24% 17% 2	4123
September	1st to 10th	Day	41% 7% 10% 18% 17% 8%	2200
	11th to 20th	Day	37% 9% 11% 20% 17% 5%	2178
	21st to end	Day	31% 7% 10% 21% 18% 13%	2090
October	1st to 10th	Day	17% 4 6% 12% 24% 36%	3480
	11th to 20th	Day	26% 3 8% 19% 24% 21%	3268
	21st to end	Day	28% 4 5% 19% 29% 16%	3428
November	1st to 10th	Day	42% 4 7% 17% 17% 12%	1958
	11th to 20th	Day	36% 4 9% 16% 20% 15%	1880
	21st to end	Day	43% 4 6% 15% 19% 13%	1800
December	1st to 10th	Day	53% 3 4 17% 14% 8%	2940
	11th to 20th	Day	43% 4 8% 12% 20% 13%	3389
	21st to end	Day	33% 3 4 18% 26% 16%	4488
January	1st to 10th	Night	38% 2 5% 19% 21% 15%	5888
	11th to 20th	Night	27% 2 4 19% 28% 20%	5900
	21st to end	Night	49% 2 3 10% 20% 15%	6144
February	1st to 10th	Night	40% 4 6% 12% 20% 18%	2400
	11th to 20th	Night	42% 2 6% 17% 18% 14%	2338
	21st to end	Night	42% 4 5% 16% 18% 15%	1980
March	1st to 10th	Night	42% 4 6% 17% 15% 17%	4972
	11th to 20th	Night	39% 4 7% 11% 13% 26%	4980
	21st to end	Night	45% 4 7% 17% 18% 10%	5467
April	1st to 10th	Night	38% 5% 10% 18% 16% 14%	2200
	11th to 20th	Night	41% 5% 9% 13% 16% 16%	2173
	21st to end	Night	44% 4 9% 18% 16% 10%	1866
May	1st to 10th	Night	51% 5% 8% 17% 14% 6%	4080
	11th to 20th	Night	33% 5% 12% 21% 20% 9%	4054
	21st to end	Night	43% 6% 14% 28% 9% 1	4452
June	1st to 10th	Night	25% 6% 16% 30% 21% 2	1800
	11th to 20th	Night	24% 6% 15% 31% 20% 5%	1800
	21st to end	Night	30% 8% 18% 28% 14% 3	1800
July	1st to 10th	Night	40% 7% 23% 26% 4 1	4035
	11th to 20th	Night	30% 6% 24% 29% 10%	4026
	21st to end	Night	35% 6% 21% 23% 12% 3	4320
August	1st to 10th	Night	11% 4 17% 47% 20%	2973
	11th to 20th	Night	20% 6% 32% 33% 7% 1	3243
	21st to end	Night	24% 11% 23% 27% 14% 2	3776
September	1st to 10th	Night	33% 7% 16% 20% 16% 7%	2200
	11th to 20th	Night	35% 8% 15% 23% 14% 5%	2178
	21st to end	Night	29% 7% 16% 20% 17% 12%	2090
October	1st to 10th	Night	17% 4 7% 15% 20% 37%	3480
	11th to 20th	Night	22% 3 9% 17% 29% 20%	3619
	21st to end	Night	26% 3 7% 19% 29% 16%	4120
November	1st to 10th	Night	36% 4 8% 18% 20% 14%	2340
	11th to 20th	Night	32% 5% 9% 17% 21% 17%	2515
	21st to end	Night	39% 3 8% 17% 19% 14%	2600
December	1st to 10th	Night	53% 3 5% 15% 13% 10%	4250
	11th to 20th	Night	44% 3 7% 9% 21% 17%	4817
	21st to end	Night	35% 3 4 14% 28% 17%	6490

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	23% 13% 38% 21% 4 1	300
	11th to 20th	Day	26% 15% 28% 24% 6% 1	300
	21st to end	Day	21% 15% 33% 24% 7%	330
February	1st to 10th	Day	32% 13% 27% 19% 9%	300
	11th to 20th	Day	29% 17% 31% 18% 4 1	300
	21st to end	Day	26% 18% 39% 15% 2	249
March	1st to 10th	Day	22% 15% 42% 18% 3	300
	11th to 20th	Day	16% 20% 40% 19% 5%	300
	21st to end	Day	22% 16% 35% 21% 5%	330
April	1st to 10th	Day	20% 16% 36% 25% 3	300
	11th to 20th	Day	20% 14% 36% 22% 8%	294
	21st to end	Day	18% 11% 39% 27% 5%	626
May	1st to 10th	Day	19% 12% 36% 25% 7%	703
	11th to 20th	Day	16% 10% 28% 35% 10% 1	725
	21st to end	Day	17% 6% 24% 37% 15% 1	789
June	1st to 10th	Day	8% 3 17% 41% 26% 5%	730
	11th to 20th	Day	10% 1 15% 45% 26% 3	730
	21st to end	Day	10% 2 13% 36% 29% 11%	730
July	1st to 10th	Day	10% 2 9% 33% 36% 10%	721
	11th to 20th	Day	6% 1 8% 28% 47% 10%	718
	21st to end	Day	6% 1 5% 33% 44% 11%	794
August	1st to 10th	Day	3 1 4 29% 46% 17%	689
	11th to 20th	Day	6% 3 37% 39% 15%	517
	21st to end	Day	4 1 7% 22% 44% 22%	473
September	1st to 10th	Day	12% 1 7% 26% 38% 16%	330
	11th to 20th	Day	7% 1 5% 25% 44% 18%	324
	21st to end	Day	10% 1 11% 24% 37% 17%	300
October	1st to 10th	Day	6% 2 14% 33% 34% 10%	300
	11th to 20th	Day	11% 5% 19% 36% 24% 4	300
	21st to end	Day	18% 12% 23% 22% 18% 6%	330
November	1st to 10th	Day	19% 10% 23% 30% 13% 4	300
	11th to 20th	Day	18% 9% 28% 27% 15% 3	300
	21st to end	Day	23% 15% 30% 19% 10% 3	300
December	1st to 10th	Day	22% 9% 33% 26% 7% 4	300
	11th to 20th	Day	22% 16% 27% 25% 9% 1	300
	21st to end	Day	22% 8% 38% 23% 8% 1	330
January	1st to 10th	Night	22% 8% 28% 33% 9%	1000
	11th to 20th	Night	21% 9% 33% 29% 8%	1000
	21st to end	Night	25% 8% 27% 33% 8%	949
February	1st to 10th	Night	26% 10% 29% 29% 6%	800
	11th to 20th	Night	27% 13% 31% 24% 4	784
	21st to end	Night	26% 13% 36% 24% 2	660
March	1st to 10th	Night	23% 13% 34% 27% 3	629
	11th to 20th	Night	21% 11% 36% 28% 5%	600
	21st to end	Night	21% 10% 39% 27% 3	660
April	1st to 10th	Night	17% 10% 41% 29% 3	600
	11th to 20th	Night	22% 11% 36% 26% 5%	593
	21st to end	Night	22% 9% 37% 25% 7% 1	600
May	1st to 10th	Night	20% 8% 39% 29% 4	600
	11th to 20th	Night	16% 6% 35% 35% 8%	591
	21st to end	Night	15% 6% 34% 35% 11%	650
June	1st to 10th	Night	8% 2 24% 46% 20% 1	600
	11th to 20th	Night	7% 2 30% 46% 16% 1	600
	21st to end	Night	8% 1 18% 43% 28% 2	600
July	1st to 10th	Night	9% 2 12% 45% 28% 3	585
	11th to 20th	Night	4 2 12% 48% 32% 2	582
	21st to end	Night	7% 1 9% 46% 34% 3	657
August	1st to 10th	Night	1 1 7% 50% 37% 5%	597
	11th to 20th	Night	4 1 8% 48% 35% 4	594
	21st to end	Night	6% 1 6% 37% 45% 5%	660
September	1st to 10th	Night	10% 1 8% 39% 38% 4	600
	11th to 20th	Night	11% 1 8% 36% 41% 3	594
	21st to end	Night	9% 2 14% 33% 39% 4	570
October	1st to 10th	Night	7% 2 10% 46% 30% 4	570
	11th to 20th	Night	15% 2 19% 40% 21% 2	665
	21st to end	Night	16% 6% 21% 35% 19% 3	836
November	1st to 10th	Night	16% 6% 18% 37% 21% 1	780
	11th to 20th	Night	15% 6% 23% 38% 16% 2	915
	21st to end	Night	20% 9% 25% 32% 13% 1	1000
December	1st to 10th	Night	22% 8% 24% 33% 12% 1	1000
	11th to 20th	Night	27% 8% 24% 31% 10%	1000
	21st to end	Night	23% 7% 28% 34% 9%	1100

Page generated at 2025-09-16 00:49:14. Version ac07

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