Rush Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rush Lake clear sky chart from 2005-11-06 to 2026-01-17.

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	12% 9% 3 8% 5% 4 4 4 5% 7% 38%	128448
	Night	12% 10% 4 9% 5% 4 4 4 5% 6% 37%	123509
Transparency	Day	44% 6% 13% 25% 11% 1	131999
	Night	45% 6% 13% 23% 12% 1	128034
Seeing	Day	16% 9% 30% 27% 14% 4	17679
	Night	16% 8% 31% 33% 11% 1	27658

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	9% 12% 5% 16% 8% 5% 4 4 4 5% 28%	3697
	11th to 20th	Day	6% 10% 6% 14% 8% 7% 8% 7% 8% 5% 22%	3668
	21st to end	Day	5% 16% 8% 12% 5% 4 5% 4 5% 6% 30%	4419
February	1st to 10th	Day	9% 13% 4 11% 6% 5% 5% 4 5% 7% 32%	1800
	11th to 20th	Day	7% 12% 4 9% 7% 5% 4 4 5% 7% 37%	1754
	21st to end	Day	10% 11% 3 10% 6% 5% 5% 3 6% 7% 35%	1544
March	1st to 10th	Day	11% 9% 3 7% 4 4 4 3 5% 7% 43%	4792
	11th to 20th	Day	9% 9% 3 8% 5% 5% 4 4 6% 8% 40%	4980
	21st to end	Day	20% 11% 4 9% 5% 4 4 3 5% 5% 29%	5549
April	1st to 10th	Day	17% 11% 4 7% 5% 5% 4 3 5% 6% 34%	2400
	11th to 20th	Day	20% 11% 4 9% 4 4 5% 3 4 5% 32%	2392
	21st to end	Day	22% 9% 3 7% 5% 5% 4 3 4 6% 32%	2600
May	1st to 10th	Day	14% 6% 2 5% 3 4 4 3 5% 6% 49%	6200
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 4 6% 42%	6319
	21st to end	Day	16% 8% 2 6% 4 4 5% 4 5% 8% 36%	6935
June	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 6% 8% 45%	2800
	11th to 20th	Day	13% 7% 3 7% 5% 4 5% 4 6% 9% 37%	2861
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 5% 7% 10% 39%	3000
July	1st to 10th	Day	8% 4 2 6% 4 5% 5% 4 7% 11% 45%	6607
	11th to 20th	Day	9% 4 2 4 3 3 4 4 6% 9% 54%	6360
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 10% 48%	6924
August	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 6% 8% 44%	4252
	11th to 20th	Day	12% 5% 2 7% 4 5% 6% 4 5% 9% 41%	4171
	21st to end	Day	11% 6% 2 7% 4 4 4 4 6% 7% 44%	4478
September	1st to 10th	Day	10% 6% 2 5% 5% 4 4 4 6% 8% 46%	2400
	11th to 20th	Day	12% 5% 2 6% 4 5% 4 4 6% 7% 45%	2385
	21st to end	Day	14% 7% 3 5% 3 4 3 3 5% 8% 45%	2094
October	1st to 10th	Day	16% 7% 2 5% 4 3 5% 4 6% 8% 41%	2000
	11th to 20th	Day	17% 11% 3 7% 4 5% 4 3 4 6% 37%	2000
	21st to end	Day	18% 11% 3 8% 5% 4 3 3 4 5% 36%	2145
November	1st to 10th	Day	12% 12% 4 9% 5% 5% 4 4 5% 6% 34%	1714
	11th to 20th	Day	13% 15% 5% 12% 5% 5% 4 3 4 6% 29%	1680
	21st to end	Day	14% 12% 4 9% 5% 4 4 5% 5% 7% 30%	1680
December	1st to 10th	Day	8% 12% 6% 15% 13% 7% 5% 3 4 5% 21%	2690
	11th to 20th	Day	11% 18% 6% 10% 5% 4 5% 3 5% 6% 27%	3088
	21st to end	Day	20% 19% 7% 18% 7% 4 3 2 3 3 14%	4070
January	1st to 10th	Night	8% 10% 5% 15% 9% 5% 4 3 4 6% 32%	6488
	11th to 20th	Night	6% 11% 5% 11% 7% 7% 10% 7% 7% 5% 23%	6445
	21st to end	Night	7% 18% 6% 10% 5% 5% 4 3 5% 5% 32%	6554
February	1st to 10th	Night	7% 12% 4 9% 6% 5% 5% 3 5% 6% 37%	2600
	11th to 20th	Night	6% 10% 3 10% 6% 6% 5% 3 5% 7% 39%	2533
	21st to end	Night	12% 10% 3 9% 6% 5% 5% 3 5% 7% 35%	2085
March	1st to 10th	Night	10% 7% 2 7% 4 4 4 3 4 6% 48%	5106
	11th to 20th	Night	10% 8% 3 8% 6% 5% 5% 4 7% 9% 35%	4980
	21st to end	Night	23% 11% 4 10% 4 4 4 3 5% 5% 29%	5379
April	1st to 10th	Night	16% 11% 3 7% 4 5% 4 3 5% 5% 37%	2000
	11th to 20th	Night	20% 11% 3 7% 4 3 3 2 4 6% 37%	1955
	21st to end	Night	21% 9% 3 6% 5% 4 5% 4 5% 6% 34%	1800
May	1st to 10th	Night	11% 6% 2 6% 5% 3 3 3 4 6% 50%	3715
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 4 7% 49%	3596
	21st to end	Night	14% 8% 3 6% 5% 4 4 3 6% 8% 38%	3942
June	1st to 10th	Night	10% 6% 3 5% 5% 4 4 4 6% 9% 46%	1600
	11th to 20th	Night	11% 5% 2 6% 4 5% 5% 3 6% 8% 44%	1530
	21st to end	Night	9% 5% 2 6% 5% 3 5% 4 6% 8% 48%	1400
July	1st to 10th	Night	8% 4 2 5% 3 4 4 4 7% 9% 50%	3354
	11th to 20th	Night	7% 4 2 5% 3 4 4 3 7% 8% 54%	3617
	21st to end	Night	8% 5% 3 6% 5% 4 4 4 5% 7% 50%	3947
August	1st to 10th	Night	11% 6% 2 6% 3 4 4 3 5% 7% 49%	2892
	11th to 20th	Night	14% 5% 2 5% 3 4 4 4 7% 8% 46%	2888
	21st to end	Night	11% 7% 3 7% 4 4 5% 3 5% 7% 45%	3423
September	1st to 10th	Night	9% 5% 2 5% 3 4 4 4 6% 7% 52%	2000
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 5% 8% 53%	2010
	21st to end	Night	14% 5% 1 4 3 4 4 4 4 7% 50%	2285
October	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 5% 6% 49%	2400
	11th to 20th	Night	15% 11% 3 6% 5% 4 4 3 5% 6% 39%	2400
	21st to end	Night	18% 10% 4 8% 5% 3 3 3 5% 6% 36%	2695
November	1st to 10th	Night	13% 9% 4 7% 5% 4 5% 3 6% 7% 37%	2801
	11th to 20th	Night	14% 12% 5% 11% 6% 4 4 3 4 5% 33%	2940
	21st to end	Night	13% 10% 4 9% 6% 4 4 4 5% 7% 34%	2940
December	1st to 10th	Night	7% 10% 4 15% 8% 8% 6% 4 5% 7% 25%	4720
	11th to 20th	Night	11% 17% 6% 13% 5% 5% 5% 6% 5% 5% 22%	5339
	21st to end	Night	21% 19% 7% 14% 5% 3 3 3 3 4 18%	7150

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	58% 6% 9% 17% 10%	3698
	11th to 20th	Day	59% 6% 9% 17% 9%	3668
	21st to end	Day	54% 6% 15% 17% 8%	4419
February	1st to 10th	Day	51% 5% 13% 22% 8% 2	1800
	11th to 20th	Day	47% 5% 13% 25% 9% 1	1763
	21st to end	Day	50% 5% 13% 21% 11% 1	1544
March	1st to 10th	Day	39% 6% 18% 24% 11% 3	4792
	11th to 20th	Day	41% 6% 14% 29% 9% 1	4980
	21st to end	Day	56% 6% 9% 20% 8% 1	5551
April	1st to 10th	Day	51% 5% 12% 19% 13% 1	2400
	11th to 20th	Day	55% 5% 10% 17% 12% 2	2392
	21st to end	Day	54% 6% 11% 20% 10%	2600
May	1st to 10th	Day	36% 5% 13% 27% 17% 2	6240
	11th to 20th	Day	42% 6% 11% 22% 13% 6%	6323
	21st to end	Day	43% 7% 10% 28% 11% 1	6949
June	1st to 10th	Day	34% 8% 15% 30% 11% 1	2800
	11th to 20th	Day	43% 7% 15% 22% 12% 1	2861
	21st to end	Day	36% 9% 18% 27% 9% 1	3000
July	1st to 10th	Day	32% 7% 18% 33% 10%	6537
	11th to 20th	Day	27% 5% 17% 37% 13% 1	6285
	21st to end	Day	31% 6% 16% 31% 15% 1	6728
August	1st to 10th	Day	36% 6% 15% 29% 13% 1	4237
	11th to 20th	Day	39% 7% 13% 33% 9%	4210
	21st to end	Day	38% 7% 17% 25% 12% 1	4477
September	1st to 10th	Day	35% 8% 15% 32% 10%	2400
	11th to 20th	Day	37% 8% 18% 30% 7%	2385
	21st to end	Day	38% 6% 13% 32% 10% 1	2094
October	1st to 10th	Day	30% 5% 12% 35% 18% 1	3260
	11th to 20th	Day	41% 5% 10% 27% 15% 2	3240
	21st to end	Day	48% 3 16% 25% 8%	3447
November	1st to 10th	Day	50% 7% 12% 19% 11% 1	1714
	11th to 20th	Day	57% 5% 12% 18% 7%	1680
	21st to end	Day	52% 7% 16% 18% 5% 2	1680
December	1st to 10th	Day	65% 6% 11% 14% 4 1	2690
	11th to 20th	Day	57% 5% 11% 20% 7%	3085
	21st to end	Day	76% 4 7% 9% 4	4070
January	1st to 10th	Night	54% 5% 11% 18% 11% 1	6488
	11th to 20th	Night	58% 7% 11% 14% 10%	6445
	21st to end	Night	53% 5% 14% 22% 6%	6554
February	1st to 10th	Night	47% 6% 13% 22% 10% 1	2600
	11th to 20th	Night	44% 7% 13% 24% 10% 1	2534
	21st to end	Night	48% 6% 13% 21% 11% 1	2085
March	1st to 10th	Night	37% 5% 15% 22% 17% 4	5106
	11th to 20th	Night	41% 7% 15% 24% 13%	4980
	21st to end	Night	59% 4 10% 16% 12%	5379
April	1st to 10th	Night	47% 6% 9% 21% 16% 1	2000
	11th to 20th	Night	49% 5% 8% 21% 14% 2	1955
	21st to end	Night	49% 8% 9% 20% 14% 2	1800
May	1st to 10th	Night	34% 6% 12% 28% 18% 2	3740
	11th to 20th	Night	35% 5% 12% 23% 18% 8%	3597
	21st to end	Night	42% 7% 10% 27% 12% 1	3950
June	1st to 10th	Night	34% 8% 15% 28% 13% 3	1600
	11th to 20th	Night	36% 6% 16% 23% 16% 2	1530
	21st to end	Night	31% 8% 15% 30% 14% 3	1400
July	1st to 10th	Night	28% 7% 19% 31% 13% 1	3317
	11th to 20th	Night	26% 6% 15% 37% 14% 2	3572
	21st to end	Night	33% 6% 15% 29% 15% 2	3832
August	1st to 10th	Night	34% 6% 12% 29% 15% 3	2883
	11th to 20th	Night	35% 7% 14% 32% 12% 1	2915
	21st to end	Night	38% 6% 17% 28% 10% 2	3423
September	1st to 10th	Night	29% 8% 15% 34% 14% 1	2000
	11th to 20th	Night	30% 6% 19% 32% 14%	2010
	21st to end	Night	34% 6% 13% 33% 13% 1	2285
October	1st to 10th	Night	25% 4 7% 36% 24% 4	3920
	11th to 20th	Night	36% 5% 12% 25% 20% 2	3899
	21st to end	Night	46% 5% 12% 25% 12%	4343
November	1st to 10th	Night	45% 7% 13% 23% 11% 1	2801
	11th to 20th	Night	54% 4 13% 19% 10% 1	2940
	21st to end	Night	49% 7% 16% 21% 6% 1	2940
December	1st to 10th	Night	57% 7% 16% 17% 3	4720
	11th to 20th	Night	62% 5% 10% 16% 5% 1	5341
	21st to end	Night	71% 4 8% 12% 4	7150

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	13% 11% 34% 28% 10% 4	330
	11th to 20th	Day	14% 9% 40% 29% 8%	318
	21st to end	Day	15% 7% 39% 25% 13% 1	330
February	1st to 10th	Day	17% 11% 41% 25% 5% 1	300
	11th to 20th	Day	15% 13% 40% 22% 8% 2	300
	21st to end	Day	18% 11% 41% 27% 3	249
March	1st to 10th	Day	17% 13% 38% 25% 6% 1	300
	11th to 20th	Day	20% 10% 36% 24% 9% 1	300
	21st to end	Day	25% 14% 28% 22% 8% 2	366
April	1st to 10th	Day	21% 17% 31% 23% 7% 1	500
	11th to 20th	Day	25% 13% 29% 23% 9% 1	510
	21st to end	Day	25% 11% 31% 21% 11% 2	700
May	1st to 10th	Day	19% 12% 30% 25% 12% 3	703
	11th to 20th	Day	18% 10% 28% 26% 13% 4	725
	21st to end	Day	20% 9% 24% 27% 16% 4	789
June	1st to 10th	Day	11% 7% 27% 33% 18% 5%	730
	11th to 20th	Day	14% 8% 33% 31% 11% 3	730
	21st to end	Day	14% 7% 28% 29% 16% 5%	730
July	1st to 10th	Day	8% 3 21% 32% 24% 12%	721
	11th to 20th	Day	8% 4 26% 31% 20% 10%	718
	21st to end	Day	6% 4 24% 36% 22% 9%	794
August	1st to 10th	Day	9% 4 22% 35% 23% 7%	726
	11th to 20th	Day	13% 5% 19% 30% 26% 7%	715
	21st to end	Day	11% 6% 23% 32% 21% 7%	684
September	1st to 10th	Day	13% 6% 26% 31% 18% 5%	530
	11th to 20th	Day	11% 6% 27% 30% 22% 4	515
	21st to end	Day	17% 9% 28% 20% 17% 9%	330
October	1st to 10th	Day	17% 9% 32% 21% 14% 7%	330
	11th to 20th	Day	18% 17% 33% 25% 7% 1	330
	21st to end	Day	23% 15% 34% 19% 7% 1	363
November	1st to 10th	Day	20% 12% 35% 24% 8% 1	330
	11th to 20th	Day	18% 18% 38% 19% 6% 1	330
	21st to end	Day	19% 14% 39% 21% 6%	330
December	1st to 10th	Day	15% 10% 40% 25% 10%	330
	11th to 20th	Day	19% 16% 36% 25% 4	330
	21st to end	Day	27% 11% 36% 22% 3 1	363
January	1st to 10th	Night	14% 9% 33% 33% 9% 1	1050
	11th to 20th	Night	15% 8% 38% 30% 8% 1	1031
	21st to end	Night	17% 9% 37% 29% 8% 1	1100
February	1st to 10th	Night	13% 10% 38% 30% 9%	1000
	11th to 20th	Night	10% 9% 44% 29% 7% 1	979
	21st to end	Night	17% 9% 34% 30% 9% 1	765
March	1st to 10th	Night	14% 11% 35% 30% 9% 1	689
	11th to 20th	Night	17% 8% 41% 28% 6%	600
	21st to end	Night	23% 9% 29% 28% 9% 2	660
April	1st to 10th	Night	20% 11% 34% 29% 7%	600
	11th to 20th	Night	24% 10% 30% 28% 8% 1	593
	21st to end	Night	25% 8% 29% 29% 8% 1	600
May	1st to 10th	Night	17% 11% 32% 33% 7% 1	600
	11th to 20th	Night	15% 8% 30% 35% 11% 1	591
	21st to end	Night	13% 7% 26% 38% 14%	650
June	1st to 10th	Night	10% 5% 29% 43% 12% 1	600
	11th to 20th	Night	12% 3 31% 44% 10%	600
	21st to end	Night	10% 5% 23% 43% 17% 1	600
July	1st to 10th	Night	6% 2 20% 45% 26% 1	585
	11th to 20th	Night	8% 2 23% 44% 21% 1	582
	21st to end	Night	4 2 22% 46% 23% 2	657
August	1st to 10th	Night	9% 3 15% 50% 21% 2	597
	11th to 20th	Night	14% 2 18% 36% 27% 3	594
	21st to end	Night	12% 3 21% 38% 25% 2	660
September	1st to 10th	Night	10% 5% 22% 42% 19% 3	600
	11th to 20th	Night	10% 4 27% 37% 20% 2	600
	21st to end	Night	15% 7% 31% 29% 17% 2	685
October	1st to 10th	Night	17% 8% 29% 33% 13% 1	800
	11th to 20th	Night	21% 10% 33% 30% 6% 1	800
	21st to end	Night	23% 11% 28% 31% 7%	880
November	1st to 10th	Night	18% 11% 31% 32% 8% 1	955
	11th to 20th	Night	20% 11% 33% 27% 8% 1	1050
	21st to end	Night	18% 12% 36% 26% 7%	1050
December	1st to 10th	Night	15% 9% 35% 32% 8% 1	1050
	11th to 20th	Night	20% 11% 35% 27% 7% 1	1050
	21st to end	Night	25% 9% 33% 26% 6% 1	1155

Page generated at 2026-01-14 00:14:25. Version ac07

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