Long Point, Glenn County
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Point, Glenn County clear sky chart from 2005-11-06 to 2026-06-01.

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	4 4 1 3 3 3 3 3 4 6% 67%	141144
	Night	5% 3 1 3 3 3 3 3 4 6% 65%	139443
Transparency	Day	21% 3 9% 20% 26% 21%	136013
	Night	22% 3 10% 20% 24% 20%	135565
Seeing	Day	10% 12% 28% 30% 16% 5%	17194
	Night	8% 7% 26% 32% 22% 5%	26459

By Month

Percentage Cloud Cover SW (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	9% 6% 2 5% 5% 4 5% 4 6% 8% 46%	4819
	11th to 20th	Day	6% 5% 2 4 3 3 3 2 4 6% 61%	5340
	21st to end	Day	9% 6% 2 5% 4 4 4 3 5% 8% 50%	5843
February	1st to 10th	Day	9% 6% 1 5% 4 5% 5% 4 5% 7% 49%	1890
	11th to 20th	Day	7% 6% 2 6% 4 5% 5% 4 6% 9% 46%	1859
	21st to end	Day	8% 6% 2 5% 5% 5% 5% 4 5% 8% 49%	1730
March	1st to 10th	Day	7% 9% 3 8% 6% 5% 4 4 5% 6% 43%	5008
	11th to 20th	Day	5% 6% 2 6% 4 4 5% 3 5% 7% 52%	5110
	21st to end	Day	8% 8% 3 7% 6% 5% 5% 4 6% 8% 41%	5649
April	1st to 10th	Day	8% 6% 2 6% 5% 3 4 4 6% 9% 47%	2520
	11th to 20th	Day	7% 5% 2 5% 3 4 3 3 6% 6% 55%	2489
	21st to end	Day	3 4 1 3 3 3 4 4 5% 9% 59%	2525
May	1st to 10th	Day	2 2 1 2 2 2 3 2 3 7% 74%	6010
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 6% 75%	6237
	21st to end	Day	2 2 1 2 1 1 2 3 3 6% 77%	7056
June	1st to 10th	Day	3 3 1 3 2 3 3 3 6% 8% 62%	2801
	11th to 20th	Day	1 1 1 2 2 2 3 2 5% 6% 76%	2800
	21st to end	Day	2 1 1 1 2 1 2 2 3 4 82%	2800
July	1st to 10th	Day	1 1 1 1 1 1 2 3 90%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 88%	6112
	21st to end	Day	1 1 1 2 4 3 3 4 81%	6402
August	1st to 10th	Day	1 1 1 1 1 2 2 3 5% 83%	5777
	11th to 20th	Day	1 1 1 1 1 1 2 2 91%	5708
	21st to end	Day	1 1 2 1 1 2 1 2 4 85%	5984
September	1st to 10th	Day	1 1 1 1 1 1 2 3 87%	2400
	11th to 20th	Day	2 2 1 2 2 2 3 2 4 5% 74%	2395
	21st to end	Day	2 2 1 2 2 1 1 2 3 5% 80%	2105
October	1st to 10th	Day	2 1 1 2 1 2 2 2 4 5% 78%	3280
	11th to 20th	Day	4 2 1 2 2 3 2 2 4 7% 72%	3261
	21st to end	Day	4 2 1 3 2 4 5% 4 6% 8% 60%	3558
November	1st to 10th	Day	4 5% 2 4 3 3 4 4 6% 8% 57%	1982
	11th to 20th	Day	7% 7% 2 5% 4 4 4 4 7% 8% 50%	1795
	21st to end	Day	6% 3 1 3 3 4 4 4 6% 7% 58%	1680
December	1st to 10th	Day	5% 3 1 4 3 3 4 4 7% 8% 58%	2700
	11th to 20th	Day	15% 10% 3 7% 5% 5% 5% 4 6% 9% 31%	3108
	21st to end	Day	12% 8% 2 7% 5% 6% 6% 4 6% 8% 36%	4092
January	1st to 10th	Night	10% 6% 1 4 4 4 5% 5% 7% 9% 46%	8075
	11th to 20th	Night	5% 4 2 4 3 3 4 3 5% 6% 62%	7650
	21st to end	Night	8% 6% 2 6% 4 4 4 4 5% 7% 50%	8371
February	1st to 10th	Night	7% 5% 2 5% 5% 4 4 4 6% 6% 51%	2730
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 4 7% 9% 49%	2646
	21st to end	Night	5% 4 1 6% 5% 4 4 4 5% 7% 54%	2076
March	1st to 10th	Night	5% 6% 2 5% 4 5% 5% 5% 7% 8% 49%	5102
	11th to 20th	Night	4 5% 1 4 3 4 4 4 5% 7% 59%	5110
	21st to end	Night	5% 5% 2 5% 4 4 5% 5% 6% 8% 49%	5566
April	1st to 10th	Night	6% 5% 1 4 4 4 4 4 6% 7% 55%	2100
	11th to 20th	Night	5% 4 1 4 3 3 5% 4 6% 6% 59%	2079
	21st to end	Night	4 4 1 3 2 2 3 3 5% 7% 66%	2090
May	1st to 10th	Night	3 2 1 2 2 2 3 2 3 5% 76%	4190
	11th to 20th	Night	1 1 1 2 2 2 2 4 5% 78%	3868
	21st to end	Night	1 1 1 1 1 2 1 2 5% 83%	4060
June	1st to 10th	Night	5% 3 1 3 3 2 3 3 5% 7% 66%	1600
	11th to 20th	Night	2 1 1 2 1 2 2 2 2 5% 82%	1600
	21st to end	Night	1 1 1 2 1 2 2 3 4 83%	1600
July	1st to 10th	Night	1 1 1 1 2 2 92%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 1 1 92%	3841
	21st to end	Night	1 1 1 1 2 2 4 87%	4472
August	1st to 10th	Night	2 1 1 1 1 2 2 2 2 86%	4035
	11th to 20th	Night	1 1 1 1 1 1 2 92%	4144
	21st to end	Night	1 1 1 1 1 1 1 2 3 87%	5015
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 89%	2000
	11th to 20th	Night	2 2 1 2 1 2 2 2 3 5% 78%	2001
	21st to end	Night	1 1 1 1 2 2 2 3 5% 82%	2295
October	1st to 10th	Night	2 1 1 1 1 2 3 2 2 4 81%	3920
	11th to 20th	Night	2 1 1 2 1 2 3 2 3 6% 76%	3897
	21st to end	Night	4 2 1 2 2 3 4 3 6% 8% 65%	4253
November	1st to 10th	Night	4 3 1 3 4 4 5% 4 6% 7% 58%	2534
	11th to 20th	Night	6% 4 1 4 3 4 5% 4 7% 9% 52%	2821
	21st to end	Night	4 3 2 4 2 3 5% 5% 6% 8% 57%	2940
December	1st to 10th	Night	6% 4 1 3 3 3 3 3 5% 8% 61%	4700
	11th to 20th	Night	14% 7% 2 6% 3 4 5% 5% 8% 10% 35%	5316
	21st to end	Night	11% 8% 3 8% 5% 6% 6% 4 5% 6% 37%	7106

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	36% 6% 16% 24% 14% 5%	4820
	11th to 20th	Day	26% 4 8% 13% 21% 29%	5340
	21st to end	Day	34% 3 11% 17% 19% 16%	5843
February	1st to 10th	Day	35% 5% 12% 18% 19% 10%	1890
	11th to 20th	Day	36% 4 11% 21% 20% 7%	1868
	21st to end	Day	34% 5% 14% 24% 18% 6%	1730
March	1st to 10th	Day	42% 4 10% 18% 21% 6%	5008
	11th to 20th	Day	33% 3 13% 21% 20% 8%	5110
	21st to end	Day	40% 6% 14% 25% 12% 2	5649
April	1st to 10th	Day	35% 5% 16% 22% 19% 3	2520
	11th to 20th	Day	29% 4 15% 24% 21% 7%	2492
	21st to end	Day	23% 4 17% 28% 23% 6%	2525
May	1st to 10th	Day	13% 2 10% 25% 30% 20%	6010
	11th to 20th	Day	13% 2 7% 21% 40% 16%	6240
	21st to end	Day	10% 3 10% 35% 36% 7%	7058
June	1st to 10th	Day	19% 5% 13% 28% 26% 8%	2801
	11th to 20th	Day	10% 3 10% 21% 38% 19%	2800
	21st to end	Day	9% 2 3 19% 34% 33%	2800
July	1st to 10th	Day	5% 1 2 11% 23% 58%	6251
	11th to 20th	Day	6% 1 2 6% 21% 64%	6037
	21st to end	Day	10% 2 5% 18% 28% 37%	6217
August	1st to 10th	Day	9% 1 2 12% 31% 44%	4206
	11th to 20th	Day	4 1 2 19% 40% 34%	4131
	21st to end	Day	8% 1 2 20% 40% 29%	4311
September	1st to 10th	Day	6% 1 2 13% 29% 49%	2400
	11th to 20th	Day	13% 3 7% 25% 35% 17%	2395
	21st to end	Day	10% 2 8% 19% 34% 28%	2105
October	1st to 10th	Day	12% 2 4 16% 24% 43%	3280
	11th to 20th	Day	16% 2 7% 28% 30% 17%	3261
	21st to end	Day	24% 2 9% 21% 33% 12%	3558
November	1st to 10th	Day	26% 3 13% 26% 21% 11%	1982
	11th to 20th	Day	31% 5% 16% 20% 18% 9%	1795
	21st to end	Day	25% 5% 13% 20% 22% 15%	1680
December	1st to 10th	Day	24% 4 10% 20% 28% 14%	2700
	11th to 20th	Day	50% 3 11% 17% 15% 4	3108
	21st to end	Day	42% 5% 18% 18% 13% 3	4092
January	1st to 10th	Night	35% 5% 20% 22% 15% 3	8075
	11th to 20th	Night	24% 4 10% 13% 21% 28%	7650
	21st to end	Night	35% 3 8% 15% 18% 20%	8371
February	1st to 10th	Night	34% 4 12% 19% 21% 11%	2730
	11th to 20th	Night	31% 5% 13% 22% 21% 7%	2648
	21st to end	Night	30% 5% 14% 26% 17% 8%	2076
March	1st to 10th	Night	32% 4 17% 19% 21% 7%	5102
	11th to 20th	Night	25% 4 15% 22% 25% 9%	5110
	21st to end	Night	31% 6% 20% 26% 14% 3	5566
April	1st to 10th	Night	28% 5% 19% 23% 20% 6%	2100
	11th to 20th	Night	24% 5% 16% 25% 21% 9%	2079
	21st to end	Night	20% 3 16% 34% 23% 5%	2090
May	1st to 10th	Night	14% 2 8% 24% 36% 17%	4187
	11th to 20th	Night	11% 2 8% 27% 34% 18%	3868
	21st to end	Night	8% 3 9% 36% 36% 9%	4060
June	1st to 10th	Night	19% 4 13% 27% 29% 7%	1600
	11th to 20th	Night	9% 2 9% 22% 36% 21%	1600
	21st to end	Night	8% 2 5% 17% 34% 35%	1600
July	1st to 10th	Night	3 1 2 10% 24% 61%	3600
	11th to 20th	Night	4 1 2 6% 18% 69%	3793
	21st to end	Night	5% 1 5% 19% 34% 37%	4345
August	1st to 10th	Night	10% 1 1 11% 30% 46%	2929
	11th to 20th	Night	3 1 2 11% 40% 43%	2995
	21st to end	Night	6% 1 2 16% 42% 34%	3608
September	1st to 10th	Night	4 1 3 13% 27% 52%	2000
	11th to 20th	Night	11% 2 6% 21% 35% 24%	2001
	21st to end	Night	9% 2 6% 22% 27% 34%	2295
October	1st to 10th	Night	11% 2 4 13% 23% 48%	3920
	11th to 20th	Night	12% 2 7% 29% 34% 15%	3897
	21st to end	Night	18% 2 8% 25% 29% 19%	4253
November	1st to 10th	Night	25% 4 15% 24% 19% 12%	2534
	11th to 20th	Night	29% 5% 17% 22% 18% 9%	2821
	21st to end	Night	24% 5% 14% 19% 23% 14%	2940
December	1st to 10th	Night	23% 4 8% 21% 27% 17%	4700
	11th to 20th	Night	44% 5% 12% 19% 17% 4	5316
	21st to end	Night	45% 7% 13% 19% 12% 4	7106

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	25% 14% 31% 19% 10% 2	252
	11th to 20th	Day	13% 14% 33% 24% 13% 3	430
	21st to end	Day	15% 15% 30% 23% 14% 3	473
February	1st to 10th	Day	18% 16% 30% 23% 10% 3	430
	11th to 20th	Day	19% 20% 30% 22% 8% 1	433
	21st to end	Day	15% 19% 36% 22% 7% 1	446
March	1st to 10th	Day	23% 21% 36% 15% 4 1	540
	11th to 20th	Day	18% 20% 32% 21% 8% 1	540
	21st to end	Day	18% 22% 36% 19% 5%	594
April	1st to 10th	Day	16% 18% 35% 22% 7% 1	540
	11th to 20th	Day	20% 17% 27% 26% 8% 2	532
	21st to end	Day	10% 16% 34% 26% 12% 3	540
May	1st to 10th	Day	10% 18% 32% 24% 13% 3	543
	11th to 20th	Day	11% 15% 26% 29% 13% 5%	568
	21st to end	Day	11% 12% 25% 29% 17% 6%	617
June	1st to 10th	Day	5% 10% 27% 36% 17% 5%	531
	11th to 20th	Day	6% 14% 31% 29% 17% 3	530
	21st to end	Day	3 8% 24% 36% 21% 8%	530
July	1st to 10th	Day	3 4 24% 43% 20% 6%	526
	11th to 20th	Day	1 4 21% 40% 24% 10%	524
	21st to end	Day	1 4 18% 43% 25% 9%	575
August	1st to 10th	Day	2 5% 24% 37% 21% 10%	527
	11th to 20th	Day	2 5% 23% 36% 24% 9%	517
	21st to end	Day	2 4 21% 41% 26% 6%	583
September	1st to 10th	Day	3 5% 24% 41% 22% 5%	530
	11th to 20th	Day	4 6% 22% 40% 24% 4	530
	21st to end	Day	4 8% 26% 36% 20% 5%	530
October	1st to 10th	Day	7% 8% 28% 32% 19% 6%	530
	11th to 20th	Day	8% 8% 26% 28% 24% 5%	530
	21st to end	Day	12% 10% 23% 33% 17% 4	583
November	1st to 10th	Day	11% 10% 28% 27% 18% 5%	458
	11th to 20th	Day	13% 7% 32% 22% 19% 7%	280
	21st to end	Day	15% 8% 25% 25% 20% 7%	220
December	1st to 10th	Day	10% 13% 27% 24% 16% 9%	220
	11th to 20th	Day	17% 11% 30% 22% 15% 6%	220
	21st to end	Day	18% 15% 26% 24% 14% 3	242
January	1st to 10th	Night	16% 7% 28% 27% 16% 6%	840
	11th to 20th	Night	12% 8% 30% 32% 13% 5%	840
	21st to end	Night	12% 5% 33% 28% 17% 5%	924
February	1st to 10th	Night	14% 9% 29% 31% 14% 3	840
	11th to 20th	Night	12% 11% 30% 28% 13% 5%	824
	21st to end	Night	12% 10% 35% 32% 10% 2	692
March	1st to 10th	Night	14% 12% 32% 26% 11% 4	840
	11th to 20th	Night	11% 11% 31% 27% 18% 2	840
	21st to end	Night	12% 13% 35% 27% 12% 2	924
April	1st to 10th	Night	12% 10% 31% 32% 12% 3	840
	11th to 20th	Night	11% 11% 31% 29% 14% 4	831
	21st to end	Night	7% 9% 32% 31% 16% 4	830
May	1st to 10th	Night	6% 7% 36% 29% 18% 3	630
	11th to 20th	Night	4 7% 27% 36% 22% 4	495
	21st to end	Night	5% 9% 24% 31% 26% 5%	455
June	1st to 10th	Night	6% 7% 23% 38% 24% 3	400
	11th to 20th	Night	3 11% 25% 38% 22% 2	400
	21st to end	Night	2 2 24% 42% 26% 4	400
July	1st to 10th	Night	1 15% 43% 36% 4	390
	11th to 20th	Night	1 1 15% 37% 39% 7%	472
	21st to end	Night	9% 34% 45% 11%	657
August	1st to 10th	Night	3 13% 34% 41% 9%	597
	11th to 20th	Night	1 2 15% 36% 37% 9%	634
	21st to end	Night	2 1 10% 37% 43% 8%	880
September	1st to 10th	Night	1 3 16% 39% 34% 8%	800
	11th to 20th	Night	3 3 13% 37% 34% 10%	800
	21st to end	Night	2 4 23% 35% 27% 10%	800
October	1st to 10th	Night	5% 6% 22% 39% 22% 7%	800
	11th to 20th	Night	4 6% 22% 35% 25% 8%	800
	21st to end	Night	9% 6% 23% 29% 23% 10%	880
November	1st to 10th	Night	8% 7% 24% 31% 24% 6%	820
	11th to 20th	Night	9% 5% 29% 35% 17% 4	840
	21st to end	Night	6% 7% 34% 31% 17% 5%	840
December	1st to 10th	Night	13% 5% 28% 33% 16% 6%	840
	11th to 20th	Night	13% 8% 31% 28% 15% 4	840
	21st to end	Night	14% 11% 32% 28% 12% 3	924

Page generated at 2026-05-28 22:53:31. Version ac07

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