Saratoga
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saratoga clear sky chart from 2005-11-06 to 2025-10-19.

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	4 3 1 4 3 3 3 3 4 6% 64%	135001
	Night	5% 5% 2 5% 4 3 4 3 5% 6% 59%	132151
Transparency	Day	21% 5% 9% 19% 26% 21%	129933
	Night	25% 6% 11% 18% 22% 18%	128206
Seeing	Day	7% 10% 24% 30% 21% 8%	16713
	Night	8% 5% 14% 36% 31% 6%	26050

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% 3 7% 4 5% 4 3 5% 8% 47%	3915
	11th to 20th	Day	7% 6% 3 8% 5% 4 4 3 4 4 52%	4100
	21st to end	Day	10% 8% 3 7% 5% 5% 5% 4 5% 7% 41%	4510
February	1st to 10th	Day	11% 7% 3 6% 6% 4 4 4 6% 6% 44%	1800
	11th to 20th	Day	10% 7% 3 6% 5% 5% 4 4 6% 7% 44%	1863
	21st to end	Day	9% 8% 3 7% 5% 4 4 4 5% 7% 45%	1650
March	1st to 10th	Day	9% 7% 3 9% 7% 6% 6% 5% 7% 8% 33%	4862
	11th to 20th	Day	6% 4 2 5% 5% 5% 6% 5% 7% 9% 46%	5000
	21st to end	Day	7% 7% 2 7% 5% 6% 6% 5% 8% 11% 35%	5573
April	1st to 10th	Day	9% 6% 2 7% 5% 4 4 3 6% 7% 47%	2400
	11th to 20th	Day	8% 6% 2 4 3 3 4 3 5% 8% 55%	2369
	21st to end	Day	5% 5% 2 4 4 4 3 3 5% 8% 58%	2400
May	1st to 10th	Day	3 2 1 2 1 2 2 2 4 5% 77%	5545
	11th to 20th	Day	2 2 1 2 1 1 1 2 2 6% 79%	5944
	21st to end	Day	2 2 1 3 2 1 2 1 3 5% 77%	6902
June	1st to 10th	Day	3 4 1 3 3 3 2 3 5% 8% 65%	2800
	11th to 20th	Day	2 2 1 1 2 2 2 4 7% 78%	2800
	21st to end	Day	1 1 1 2 1 2 2 2 3 5% 81%	2800
July	1st to 10th	Day	1 1 1 1 1 2 3 90%	6305
	11th to 20th	Day	1 1 1 1 1 1 2 4 85%	5880
	21st to end	Day	1 1 2 1 2 1 2 3 7% 79%	6402
August	1st to 10th	Day	1 1 2 2 2 2 2 4 6% 80%	5777
	11th to 20th	Day	1 1 1 1 1 2 1 2 4 85%	5474
	21st to end	Day	1 2 3 3 2 2 3 6% 79%	5984
September	1st to 10th	Day	1 1 2 2 1 2 1 2 5% 82%	2400
	11th to 20th	Day	2 3 1 4 3 2 4 3 4 8% 67%	2400
	21st to end	Day	2 1 1 2 2 2 2 2 4 5% 76%	2126
October	1st to 10th	Day	1 2 1 2 2 3 3 3 4 6% 73%	3280
	11th to 20th	Day	2 3 1 3 2 3 3 3 4 6% 71%	3242
	21st to end	Day	2 3 1 3 3 3 3 3 6% 8% 65%	3448
November	1st to 10th	Day	5% 5% 2 5% 4 4 5% 3 5% 8% 54%	1928
	11th to 20th	Day	5% 6% 2 6% 5% 5% 4 5% 5% 8% 51%	1800
	21st to end	Day	8% 5% 2 5% 4 4 4 4 4 8% 53%	1670
December	1st to 10th	Day	4 3 2 5% 5% 4 4 4 7% 9% 53%	2620
	11th to 20th	Day	10% 6% 3 8% 6% 7% 6% 5% 7% 8% 35%	3028
	21st to end	Day	8% 9% 3 10% 6% 7% 7% 5% 7% 7% 30%	4004
January	1st to 10th	Night	8% 6% 3 6% 5% 4 4 4 5% 8% 48%	6026
	11th to 20th	Night	7% 6% 3 10% 5% 4 4 3 4 5% 48%	5880
	21st to end	Night	9% 9% 3 9% 5% 5% 5% 3 5% 6% 43%	6468
February	1st to 10th	Night	8% 7% 2 7% 6% 4 5% 3 4 6% 48%	2600
	11th to 20th	Night	9% 7% 3 6% 5% 4 5% 4 6% 8% 44%	2424
	21st to end	Night	9% 6% 2 6% 4 4 4 3 6% 7% 50%	1980
March	1st to 10th	Night	10% 9% 3 9% 7% 6% 5% 4 6% 6% 36%	5029
	11th to 20th	Night	8% 7% 3 6% 5% 5% 4 3 4 7% 49%	5000
	21st to end	Night	8% 11% 3 7% 5% 5% 5% 4 5% 6% 40%	5402
April	1st to 10th	Night	7% 6% 3 6% 5% 4 5% 3 6% 7% 48%	2000
	11th to 20th	Night	6% 6% 2 6% 3 4 4 3 5% 7% 54%	1979
	21st to end	Night	3 4 1 4 2 3 4 4 6% 10% 59%	2000
May	1st to 10th	Night	1 3 1 3 2 3 3 2 3 5% 74%	4432
	11th to 20th	Night	1 2 1 3 2 2 2 3 5% 7% 73%	3946
	21st to end	Night	1 2 1 2 2 1 2 2 3 6% 77%	3972
June	1st to 10th	Night	2 3 1 4 2 2 2 3 5% 9% 66%	1600
	11th to 20th	Night	1 1 3 1 2 3 3 8% 77%	1600
	21st to end	Night	1 2 1 2 2 2 3 2 3 4 80%	1600
July	1st to 10th	Night	1 1 1 1 1 2 3 91%	3640
	11th to 20th	Night	1 1 3 2 2 1 1 3 5% 82%	4096
	21st to end	Night	3 1 4 3 2 2 2 7% 9% 68%	4472
August	1st to 10th	Night	1 1 1 3 3 2 2 2 3 6% 75%	4035
	11th to 20th	Night	1 1 2 2 1 2 1 3 4 82%	4390
	21st to end	Night	1 1 3 3 2 3 2 3 5% 77%	5015
September	1st to 10th	Night	1 1 1 3 2 1 3 2 3 7% 77%	2000
	11th to 20th	Night	2 4 1 4 2 3 3 3 4 6% 68%	2000
	21st to end	Night	2 2 1 3 2 2 2 2 3 6% 75%	2268
October	1st to 10th	Night	2 2 1 2 1 2 3 2 4 6% 76%	3920
	11th to 20th	Night	2 5% 2 4 3 2 2 2 4 6% 67%	3873
	21st to end	Night	3 3 1 4 3 3 3 3 5% 7% 65%	4121
November	1st to 10th	Night	4 5% 1 4 4 4 4 3 6% 7% 57%	2370
	11th to 20th	Night	6% 5% 2 6% 4 4 4 4 7% 7% 52%	2600
	21st to end	Night	6% 5% 2 5% 4 4 4 3 5% 7% 55%	2725
December	1st to 10th	Night	4 4 2 5% 4 3 4 4 5% 6% 58%	4560
	11th to 20th	Night	10% 8% 3 8% 5% 5% 5% 4 8% 10% 33%	5176
	21st to end	Night	10% 7% 3 10% 7% 8% 7% 5% 6% 7% 30%	6952

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	32% 9% 17% 23% 15% 5%	3915
	11th to 20th	Day	34% 6% 8% 13% 19% 20%	4100
	21st to end	Day	40% 7% 6% 13% 18% 16%	4510
February	1st to 10th	Day	40% 4 7% 20% 18% 11%	1800
	11th to 20th	Day	38% 6% 10% 18% 21% 7%	1872
	21st to end	Day	39% 5% 8% 22% 18% 7%	1650
March	1st to 10th	Day	44% 11% 8% 15% 19% 2	4862
	11th to 20th	Day	29% 11% 13% 28% 12% 7%	5000
	21st to end	Day	37% 12% 18% 20% 11% 2	5573
April	1st to 10th	Day	36% 5% 12% 22% 21% 4	2400
	11th to 20th	Day	28% 6% 13% 25% 21% 6%	2372
	21st to end	Day	25% 4 14% 29% 23% 5%	2400
May	1st to 10th	Day	12% 3 6% 30% 35% 14%	5545
	11th to 20th	Day	10% 2 17% 28% 33% 10%	5947
	21st to end	Day	12% 3 11% 28% 41% 6%	6904
June	1st to 10th	Day	19% 5% 13% 26% 29% 8%	2800
	11th to 20th	Day	9% 4 11% 22% 36% 18%	2800
	21st to end	Day	10% 1 6% 15% 32% 36%	2800
July	1st to 10th	Day	4 1 2 8% 22% 64%	6237
	11th to 20th	Day	5% 1 4 8% 17% 65%	5811
	21st to end	Day	7% 3 5% 19% 30% 36%	6217
August	1st to 10th	Day	10% 3 4 15% 30% 38%	4206
	11th to 20th	Day	5% 2 4 11% 38% 41%	3955
	21st to end	Day	7% 2 6% 15% 34% 35%	4311
September	1st to 10th	Day	8% 2 5% 12% 31% 42%	2400
	11th to 20th	Day	16% 4 9% 23% 31% 17%	2400
	21st to end	Day	11% 3 7% 20% 35% 24%	2126
October	1st to 10th	Day	13% 3 5% 11% 28% 39%	3280
	11th to 20th	Day	15% 4 8% 24% 32% 17%	3242
	21st to end	Day	17% 5% 8% 23% 29% 19%	3448
November	1st to 10th	Day	28% 6% 9% 22% 24% 12%	1928
	11th to 20th	Day	30% 7% 10% 22% 23% 9%	1800
	21st to end	Day	31% 3 9% 17% 30% 10%	1670
December	1st to 10th	Day	27% 5% 9% 18% 33% 9%	2620
	11th to 20th	Day	44% 8% 10% 15% 15% 7%	3028
	21st to end	Day	48% 11% 11% 17% 10% 3	4004
January	1st to 10th	Night	29% 9% 19% 22% 16% 4	6026
	11th to 20th	Night	35% 8% 10% 11% 23% 14%	5880
	21st to end	Night	39% 9% 7% 11% 17% 18%	6468
February	1st to 10th	Night	38% 4 8% 18% 20% 12%	2600
	11th to 20th	Night	36% 5% 11% 19% 22% 7%	2426
	21st to end	Night	32% 5% 11% 29% 17% 6%	1980
March	1st to 10th	Night	44% 10% 11% 14% 17% 4	5029
	11th to 20th	Night	32% 9% 13% 21% 17% 7%	5000
	21st to end	Night	39% 12% 13% 22% 11% 3	5402
April	1st to 10th	Night	33% 6% 15% 22% 19% 5%	2000
	11th to 20th	Night	29% 6% 14% 26% 18% 8%	1979
	21st to end	Night	20% 6% 17% 29% 22% 7%	2000
May	1st to 10th	Night	13% 5% 11% 26% 28% 17%	4429
	11th to 20th	Night	12% 5% 27% 27% 22% 8%	3947
	21st to end	Night	11% 4 16% 22% 39% 8%	3972
June	1st to 10th	Night	16% 5% 16% 27% 27% 10%	1600
	11th to 20th	Night	9% 4 10% 21% 31% 25%	1600
	21st to end	Night	12% 2 8% 18% 26% 35%	1600
July	1st to 10th	Night	3 1 3 9% 22% 62%	3600
	11th to 20th	Night	5% 2 5% 13% 16% 58%	4043
	21st to end	Night	12% 4 10% 15% 24% 35%	4345
August	1st to 10th	Night	13% 2 5% 20% 24% 36%	2929
	11th to 20th	Night	7% 3 7% 10% 29% 45%	3178
	21st to end	Night	9% 3 7% 17% 30% 34%	3608
September	1st to 10th	Night	8% 3 5% 15% 27% 43%	2000
	11th to 20th	Night	16% 4 10% 23% 29% 18%	2000
	21st to end	Night	12% 3 7% 18% 32% 27%	2268
October	1st to 10th	Night	12% 3 7% 10% 21% 46%	3920
	11th to 20th	Night	18% 6% 7% 23% 28% 19%	3873
	21st to end	Night	19% 5% 7% 21% 26% 22%	4121
November	1st to 10th	Night	25% 6% 8% 25% 22% 15%	2370
	11th to 20th	Night	29% 6% 10% 23% 23% 9%	2600
	21st to end	Night	29% 3 10% 20% 24% 14%	2725
December	1st to 10th	Night	26% 5% 7% 20% 27% 14%	4560
	11th to 20th	Night	44% 8% 10% 14% 18% 6%	5176
	21st to end	Night	48% 12% 13% 14% 9% 4	6952

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	22% 13% 29% 20% 13% 2	320
	11th to 20th	Day	14% 11% 29% 29% 14% 4	400
	21st to end	Day	13% 12% 28% 28% 15% 4	440
February	1st to 10th	Day	16% 18% 28% 23% 11% 5%	400
	11th to 20th	Day	16% 18% 31% 23% 10% 2	450
	21st to end	Day	12% 15% 33% 28% 11% 2	414
March	1st to 10th	Day	17% 15% 33% 25% 9% 1	500
	11th to 20th	Day	16% 18% 26% 24% 13% 4	500
	21st to end	Day	12% 19% 33% 25% 9% 2	550
April	1st to 10th	Day	11% 16% 32% 25% 12% 4	500
	11th to 20th	Day	11% 16% 29% 24% 14% 6%	492
	21st to end	Day	7% 19% 26% 28% 13% 7%	500
May	1st to 10th	Day	8% 13% 32% 27% 15% 5%	503
	11th to 20th	Day	8% 12% 30% 27% 15% 8%	528
	21st to end	Day	5% 10% 26% 31% 20% 8%	573
June	1st to 10th	Day	4 9% 26% 30% 23% 7%	530
	11th to 20th	Day	2 9% 30% 34% 18% 7%	530
	21st to end	Day	1 4 22% 35% 26% 11%	530
July	1st to 10th	Day	1 2 17% 38% 32% 10%	526
	11th to 20th	Day	1 1 12% 39% 33% 14%	524
	21st to end	Day	1 1 13% 38% 31% 17%	575
August	1st to 10th	Day	2 2 20% 36% 28% 14%	527
	11th to 20th	Day	1 20% 38% 24% 16%	517
	21st to end	Day	1 14% 40% 30% 15%	583
September	1st to 10th	Day	2 3 16% 38% 30% 12%	530
	11th to 20th	Day	3 5% 24% 34% 24% 10%	530
	21st to end	Day	3 7% 20% 33% 28% 9%	530
October	1st to 10th	Day	2 8% 21% 30% 26% 12%	530
	11th to 20th	Day	5% 10% 20% 28% 26% 11%	523
	21st to end	Day	6% 7% 23% 32% 25% 7%	539
November	1st to 10th	Day	7% 12% 22% 25% 25% 9%	464
	11th to 20th	Day	5% 10% 21% 30% 24% 10%	300
	21st to end	Day	7% 11% 25% 29% 23% 6%	235
December	1st to 10th	Day	8% 9% 22% 30% 22% 10%	200
	11th to 20th	Day	10% 14% 25% 22% 21% 9%	200
	21st to end	Day	12% 20% 27% 23% 15% 4	220
January	1st to 10th	Night	15% 5% 17% 34% 23% 6%	800
	11th to 20th	Night	11% 7% 15% 37% 23% 8%	800
	21st to end	Night	15% 4 14% 37% 24% 6%	880
February	1st to 10th	Night	12% 9% 15% 37% 22% 5%	800
	11th to 20th	Night	14% 8% 17% 37% 18% 5%	784
	21st to end	Night	12% 8% 19% 38% 19% 3	660
March	1st to 10th	Night	13% 10% 18% 36% 21% 3	800
	11th to 20th	Night	14% 8% 18% 34% 22% 5%	800
	21st to end	Night	10% 8% 22% 38% 20% 2	880
April	1st to 10th	Night	11% 6% 22% 37% 23% 3	800
	11th to 20th	Night	10% 11% 18% 35% 22% 4	791
	21st to end	Night	5% 7% 25% 33% 24% 6%	800
May	1st to 10th	Night	4 3 26% 36% 26% 5%	750
	11th to 20th	Night	3 3 13% 39% 36% 6%	542
	21st to end	Night	2 5% 15% 42% 33% 3	433
June	1st to 10th	Night	4 3 16% 44% 30% 4	400
	11th to 20th	Night	1 3 13% 51% 32% 1	400
	21st to end	Night	1 9% 42% 45% 3	400
July	1st to 10th	Night	1 5% 38% 52% 4	390
	11th to 20th	Night	1 2 31% 54% 12%	579
	21st to end	Night	2 1 29% 59% 9%	657
August	1st to 10th	Night	3 3 34% 51% 9%	597
	11th to 20th	Night	1 9% 38% 45% 6%	739
	21st to end	Night	1 1 7% 34% 48% 9%	880
September	1st to 10th	Night	2 1 8% 36% 44% 10%	800
	11th to 20th	Night	4 1 10% 38% 39% 7%	800
	21st to end	Night	3 2 10% 36% 40% 9%	800
October	1st to 10th	Night	4 2 10% 38% 36% 10%	800
	11th to 20th	Night	5% 5% 9% 32% 38% 10%	792
	21st to end	Night	5% 4 10% 35% 32% 14%	836
November	1st to 10th	Night	6% 3 14% 33% 34% 9%	780
	11th to 20th	Night	8% 3 14% 37% 31% 7%	800
	21st to end	Night	9% 5% 14% 40% 25% 7%	800
December	1st to 10th	Night	10% 5% 17% 36% 26% 6%	800
	11th to 20th	Night	15% 6% 15% 38% 22% 4	800
	21st to end	Night	14% 8% 21% 34% 19% 3	880

Page generated at 2025-10-15 22:50:23. Version ac07

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