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 2024-06-17.

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	13% 9% 3 8% 5% 5% 5% 4 5% 7% 37%	89788
	Night	12% 10% 4 8% 5% 4 4 3 5% 6% 38%	89110
Transparency	Day	46% 7% 13% 23% 10% 1	89540
	Night	46% 7% 13% 23% 11% 1	88963
Seeing	Day	16% 9% 30% 27% 14% 4	15477
	Night	16% 8% 31% 33% 11% 1	25463

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	13% 15% 5% 15% 7% 4 4 4 4 5% 24%	2527
	11th to 20th	Day	6% 10% 5% 14% 9% 10% 9% 5% 5% 5% 21%	2530
	21st to end	Day	7% 19% 9% 12% 6% 5% 5% 4 5% 6% 24%	3080
February	1st to 10th	Day	9% 12% 4 11% 6% 4 5% 4 5% 7% 33%	1710
	11th to 20th	Day	7% 12% 4 9% 6% 4 4 4 5% 7% 37%	1664
	21st to end	Day	10% 11% 3 10% 6% 5% 5% 3 6% 6% 34%	1469
March	1st to 10th	Day	10% 11% 3 8% 5% 5% 4 4 5% 6% 38%	3334
	11th to 20th	Day	9% 9% 3 9% 5% 5% 4 4 5% 8% 40%	3480
	21st to end	Day	20% 12% 4 10% 6% 5% 5% 4 5% 5% 25%	3873
April	1st to 10th	Day	17% 10% 4 7% 5% 5% 4 3 5% 6% 34%	2280
	11th to 20th	Day	20% 11% 4 9% 5% 4 4 3 4 5% 32%	2271
	21st to end	Day	22% 9% 3 7% 5% 5% 4 3 4 5% 31%	2470
May	1st to 10th	Day	17% 7% 2 7% 4 4 4 3 5% 6% 40%	4322
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 5% 7% 43%	4399
	21st to end	Day	18% 7% 2 7% 5% 5% 5% 4 5% 8% 34%	4824
June	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 6% 8% 46%	2660
	11th to 20th	Day	11% 7% 3 7% 4 4 5% 4 6% 9% 39%	2662
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 5% 7% 10% 39%	2700
July	1st to 10th	Day	6% 4 1 5% 4 4 4 4 7% 10% 51%	2624
	11th to 20th	Day	8% 4 2 5% 4 4 3 4 7% 9% 49%	2520
	21st to end	Day	6% 4 1 5% 4 5% 4 4 7% 10% 50%	2743
August	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 5% 8% 8% 43%	2345
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 4 5% 7% 45%	2301
	21st to end	Day	10% 6% 1 5% 3 3 4 3 6% 7% 51%	2467
September	1st to 10th	Day	10% 6% 2 5% 5% 4 4 4 6% 7% 45%	2160
	11th to 20th	Day	12% 5% 2 6% 4 5% 4 4 5% 7% 46%	2147
	21st to end	Day	16% 7% 3 5% 4 4 3 4 5% 8% 41%	1886
October	1st to 10th	Day	18% 8% 2 5% 4 3 5% 4 6% 7% 39%	1800
	11th to 20th	Day	17% 11% 3 8% 4 5% 4 3 5% 6% 35%	1800
	21st to end	Day	19% 11% 3 8% 5% 4 3 3 4 6% 36%	1931
November	1st to 10th	Day	12% 13% 4 8% 5% 5% 4 4 5% 6% 34%	1548
	11th to 20th	Day	13% 15% 6% 12% 6% 5% 4 3 4 6% 27%	1520
	21st to end	Day	14% 12% 4 8% 5% 4 4 5% 6% 7% 32%	1520
December	1st to 10th	Day	11% 14% 6% 12% 7% 6% 6% 3 5% 5% 25%	1520
	11th to 20th	Day	12% 15% 6% 10% 6% 5% 5% 3 4 6% 26%	1918
	21st to end	Day	24% 17% 6% 13% 6% 3 3 2 3 4 18%	2783
January	1st to 10th	Night	12% 13% 6% 14% 6% 4 4 3 4 5% 30%	4428
	11th to 20th	Night	6% 11% 5% 14% 8% 7% 9% 5% 7% 5% 22%	4440
	21st to end	Night	9% 22% 7% 11% 5% 4 4 3 4 4 25%	4582
February	1st to 10th	Night	6% 12% 4 9% 6% 5% 5% 3 5% 6% 37%	2470
	11th to 20th	Night	6% 10% 3 10% 6% 6% 5% 3 5% 7% 39%	2403
	21st to end	Night	13% 11% 3 8% 6% 5% 5% 3 5% 7% 35%	1984
March	1st to 10th	Night	8% 8% 3 7% 5% 4 4 3 5% 6% 46%	3550
	11th to 20th	Night	9% 9% 3 9% 6% 5% 5% 4 5% 6% 40%	3480
	21st to end	Night	24% 11% 4 10% 5% 3 3 2 4 4 29%	3757
April	1st to 10th	Night	16% 12% 3 7% 4 4 4 3 5% 5% 36%	1900
	11th to 20th	Night	21% 11% 3 7% 4 3 4 2 4 5% 37%	1856
	21st to end	Night	21% 8% 3 6% 4 4 5% 4 5% 6% 34%	1710
May	1st to 10th	Night	13% 7% 3 8% 6% 4 4 3 4 7% 40%	2583
	11th to 20th	Night	15% 5% 2 4 3 3 4 2 5% 7% 50%	2506
	21st to end	Night	13% 8% 3 7% 4 4 4 3 6% 8% 39%	2743
June	1st to 10th	Night	10% 6% 3 5% 5% 4 4 4 5% 8% 46%	1520
	11th to 20th	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 46%	1433
	21st to end	Night	8% 4 2 5% 5% 3 5% 4 7% 8% 48%	1260
July	1st to 10th	Night	4 4 1 4 3 5% 4 4 8% 9% 56%	1332
	11th to 20th	Night	7% 4 2 5% 4 4 4 3 7% 8% 53%	1440
	21st to end	Night	4 2 1 4 3 4 4 4 6% 8% 60%	1575
August	1st to 10th	Night	7% 4 2 5% 4 4 4 3 6% 9% 52%	1592
	11th to 20th	Night	13% 5% 1 4 3 3 4 3 5% 7% 52%	1600
	21st to end	Night	10% 5% 2 5% 4 4 4 3 3 6% 54%	1887
September	1st to 10th	Night	9% 5% 2 5% 3 4 4 4 6% 7% 52%	1800
	11th to 20th	Night	9% 5% 2 4 4 3 4 4 5% 8% 53%	1808
	21st to end	Night	15% 5% 2 4 3 4 4 4 4 7% 47%	2056
October	1st to 10th	Night	15% 6% 2 6% 4 3 4 3 5% 6% 46%	2160
	11th to 20th	Night	16% 11% 3 6% 5% 4 4 3 5% 6% 38%	2160
	21st to end	Night	18% 10% 4 8% 5% 3 3 3 5% 6% 36%	2425
November	1st to 10th	Night	13% 9% 4 6% 5% 4 5% 3 6% 7% 38%	2527
	11th to 20th	Night	15% 12% 5% 11% 6% 4 4 3 4 5% 32%	2660
	21st to end	Night	13% 10% 4 7% 5% 4 4 4 5% 7% 36%	2660
December	1st to 10th	Night	10% 13% 4 12% 7% 5% 4 4 5% 7% 28%	2660
	11th to 20th	Night	11% 15% 5% 11% 6% 5% 5% 4 5% 6% 26%	3279
	21st to end	Night	23% 18% 5% 9% 5% 4 3 3 3 4 22%	4884

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% 7% 11% 17% 4	2528
	11th to 20th	Day	62% 8% 10% 15% 5%	2530
	21st to end	Day	60% 8% 12% 15% 5%	3080
February	1st to 10th	Day	50% 5% 14% 23% 8% 1	1710
	11th to 20th	Day	47% 5% 14% 24% 8% 1	1673
	21st to end	Day	51% 5% 12% 21% 11% 1	1469
March	1st to 10th	Day	45% 7% 15% 23% 10% 1	3334
	11th to 20th	Day	40% 7% 13% 30% 9% 1	3480
	21st to end	Day	59% 7% 9% 19% 5%	3873
April	1st to 10th	Day	51% 5% 12% 19% 13% 1	2280
	11th to 20th	Day	55% 5% 9% 18% 12% 1	2271
	21st to end	Day	54% 6% 11% 19% 9%	2470
May	1st to 10th	Day	42% 7% 13% 24% 13% 1	4362
	11th to 20th	Day	39% 7% 13% 26% 12% 2	4403
	21st to end	Day	46% 9% 13% 23% 9% 1	4837
June	1st to 10th	Day	34% 9% 15% 30% 11% 1	2660
	11th to 20th	Day	40% 8% 15% 23% 13% 1	2662
	21st to end	Day	35% 10% 18% 27% 8% 1	2700
July	1st to 10th	Day	27% 10% 15% 32% 15% 1	2554
	11th to 20th	Day	30% 8% 16% 27% 16% 3	2445
	21st to end	Day	28% 8% 18% 29% 16% 1	2591
August	1st to 10th	Day	35% 9% 16% 29% 9% 3	2330
	11th to 20th	Day	37% 8% 15% 29% 11%	2301
	21st to end	Day	31% 8% 15% 30% 15% 1	2467
September	1st to 10th	Day	35% 8% 14% 32% 11%	2160
	11th to 20th	Day	36% 9% 17% 30% 7%	2147
	21st to end	Day	40% 7% 14% 31% 8%	1886
October	1st to 10th	Day	42% 8% 14% 26% 9% 1	1800
	11th to 20th	Day	49% 7% 12% 21% 10% 1	1800
	21st to end	Day	51% 5% 13% 22% 8%	1931
November	1st to 10th	Day	49% 7% 12% 19% 12% 1	1548
	11th to 20th	Day	59% 6% 12% 16% 7%	1520
	21st to end	Day	50% 7% 17% 19% 5% 2	1520
December	1st to 10th	Day	60% 8% 14% 14% 4	1520
	11th to 20th	Day	58% 7% 15% 15% 4	1915
	21st to end	Day	70% 5% 8% 11% 6%	2783
January	1st to 10th	Night	55% 7% 12% 19% 6% 1	4428
	11th to 20th	Night	59% 9% 12% 14% 5%	4440
	21st to end	Night	62% 6% 10% 18% 5% 1	4582
February	1st to 10th	Night	47% 6% 13% 23% 10% 1	2470
	11th to 20th	Night	44% 8% 14% 24% 9% 2	2404
	21st to end	Night	48% 6% 13% 21% 11% 1	1984
March	1st to 10th	Night	38% 7% 13% 25% 16% 2	3550
	11th to 20th	Night	40% 8% 11% 26% 14%	3480
	21st to end	Night	59% 4 8% 19% 9% 1	3757
April	1st to 10th	Night	48% 6% 9% 20% 16% 1	1900
	11th to 20th	Night	49% 5% 7% 21% 15% 2	1856
	21st to end	Night	48% 8% 9% 20% 13% 2	1710
May	1st to 10th	Night	42% 8% 12% 21% 16% 1	2608
	11th to 20th	Night	33% 6% 12% 27% 19% 3	2507
	21st to end	Night	41% 9% 12% 23% 13% 1	2751
June	1st to 10th	Night	33% 8% 16% 27% 13% 3	1520
	11th to 20th	Night	35% 6% 15% 24% 17% 3	1433
	21st to end	Night	30% 8% 16% 30% 13% 3	1260
July	1st to 10th	Night	22% 8% 18% 33% 18% 1	1293
	11th to 20th	Night	27% 8% 14% 31% 16% 4	1392
	21st to end	Night	21% 7% 17% 32% 20% 4	1487
August	1st to 10th	Night	30% 7% 14% 32% 14% 4	1583
	11th to 20th	Night	32% 7% 15% 30% 15% 2	1600
	21st to end	Night	32% 6% 13% 30% 17% 3	1887
September	1st to 10th	Night	29% 8% 14% 33% 15% 1	1800
	11th to 20th	Night	29% 6% 18% 33% 14%	1808
	21st to end	Night	36% 6% 14% 32% 11% 1	2056
October	1st to 10th	Night	38% 6% 11% 31% 13% 1	2160
	11th to 20th	Night	45% 7% 13% 23% 12% 1	2160
	21st to end	Night	49% 6% 13% 22% 10% 1	2425
November	1st to 10th	Night	44% 7% 13% 23% 11% 1	2527
	11th to 20th	Night	55% 4 13% 17% 10%	2660
	21st to end	Night	47% 7% 17% 22% 6% 1	2660
December	1st to 10th	Night	55% 6% 15% 18% 5%	2660
	11th to 20th	Night	58% 7% 11% 17% 5% 2	3281
	21st to end	Night	65% 5% 11% 15% 5%	4884

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% 33% 28% 11% 4	270
	11th to 20th	Day	14% 10% 39% 30% 8%	270
	21st to end	Day	15% 6% 38% 26% 14% 1	297
February	1st to 10th	Day	17% 10% 40% 25% 5% 1	270
	11th to 20th	Day	17% 14% 39% 22% 7% 2	270
	21st to end	Day	18% 10% 40% 28% 3	225
March	1st to 10th	Day	17% 12% 37% 25% 7% 1	270
	11th to 20th	Day	20% 9% 36% 25% 9% 1	270
	21st to end	Day	25% 13% 27% 23% 9% 3	331
April	1st to 10th	Day	22% 17% 31% 23% 7% 1	460
	11th to 20th	Day	26% 12% 28% 23% 10% 1	469
	21st to end	Day	25% 10% 31% 20% 11% 2	650
May	1st to 10th	Day	20% 12% 31% 25% 10% 2	653
	11th to 20th	Day	18% 11% 29% 26% 13% 4	675
	21st to end	Day	20% 9% 24% 27% 16% 4	734
June	1st to 10th	Day	11% 7% 26% 33% 18% 5%	680
	11th to 20th	Day	12% 7% 34% 32% 12% 3	662
	21st to end	Day	12% 7% 27% 31% 18% 6%	630
July	1st to 10th	Day	8% 3 22% 30% 24% 12%	621
	11th to 20th	Day	8% 5% 27% 31% 21% 9%	618
	21st to end	Day	7% 4 23% 35% 22% 9%	684
August	1st to 10th	Day	8% 4 21% 36% 24% 7%	626
	11th to 20th	Day	13% 5% 19% 30% 25% 8%	615
	21st to end	Day	11% 6% 23% 32% 21% 7%	586
September	1st to 10th	Day	14% 5% 27% 31% 19% 4	450
	11th to 20th	Day	11% 5% 28% 28% 23% 4	437
	21st to end	Day	21% 11% 30% 20% 13% 7%	270
October	1st to 10th	Day	19% 7% 31% 20% 15% 8%	270
	11th to 20th	Day	16% 17% 31% 25% 9% 1	270
	21st to end	Day	23% 16% 35% 18% 7% 1	297
November	1st to 10th	Day	21% 10% 34% 24% 10% 1	270
	11th to 20th	Day	17% 17% 40% 20% 6%	270
	21st to end	Day	20% 14% 40% 20% 6%	270
December	1st to 10th	Day	14% 11% 40% 24% 11%	270
	11th to 20th	Day	20% 15% 35% 25% 5%	270
	21st to end	Day	27% 12% 35% 23% 2 1	297
January	1st to 10th	Night	14% 9% 34% 33% 9% 1	950
	11th to 20th	Night	15% 7% 38% 31% 8% 1	950
	21st to end	Night	18% 9% 36% 29% 8% 1	1045
February	1st to 10th	Night	12% 9% 37% 31% 10%	950
	11th to 20th	Night	10% 9% 43% 29% 8% 1	929
	21st to end	Night	18% 9% 34% 30% 9% 1	728
March	1st to 10th	Night	14% 11% 35% 30% 9% 1	655
	11th to 20th	Night	17% 8% 40% 29% 6%	570
	21st to end	Night	22% 9% 29% 27% 10% 2	627
April	1st to 10th	Night	19% 10% 35% 28% 6%	570
	11th to 20th	Night	25% 9% 29% 28% 8% 1	563
	21st to end	Night	24% 8% 29% 30% 9% 1	570
May	1st to 10th	Night	17% 11% 33% 32% 6% 1	570
	11th to 20th	Night	15% 7% 30% 35% 11% 1	561
	21st to end	Night	13% 7% 26% 38% 15%	617
June	1st to 10th	Night	10% 5% 29% 43% 12% 1	570
	11th to 20th	Night	12% 2 31% 44% 10%	561
	21st to end	Night	9% 5% 22% 44% 19% 1	540
July	1st to 10th	Night	6% 2 20% 45% 27% 1	525
	11th to 20th	Night	8% 2 24% 44% 21% 1	522
	21st to end	Night	4 3 22% 46% 23% 2	591
August	1st to 10th	Night	8% 2 15% 52% 21% 2	537
	11th to 20th	Night	14% 2 19% 35% 27% 3	534
	21st to end	Night	12% 3 21% 38% 25% 2	594
September	1st to 10th	Night	10% 4 23% 41% 19% 3	540
	11th to 20th	Night	10% 4 29% 36% 20% 2	540
	21st to end	Night	16% 7% 33% 27% 15% 1	616
October	1st to 10th	Night	18% 7% 28% 32% 13% 1	720
	11th to 20th	Night	21% 10% 33% 30% 6% 1	720
	21st to end	Night	23% 11% 27% 31% 8%	792
November	1st to 10th	Night	19% 10% 30% 32% 8% 1	861
	11th to 20th	Night	19% 11% 34% 28% 8% 1	950
	21st to end	Night	18% 12% 36% 27% 8%	950
December	1st to 10th	Night	16% 9% 34% 32% 8% 1	950
	11th to 20th	Night	20% 9% 35% 27% 7% 1	950
	21st to end	Night	25% 9% 34% 26% 6%	1045

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