Chamberlain Creek Rest Stop
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chamberlain Creek Rest Stop clear sky chart from 2005-11-06 to 2026-04-02.

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	11% 5% 2 4 3 3 3 3 4 6% 57%	140303
	Night	14% 7% 3 6% 3 3 3 3 4 5% 49%	138991
Transparency	Day	29% 4 9% 21% 21% 15%	135154
	Night	36% 5% 10% 18% 18% 13%	135134
Seeing	Day	16% 11% 26% 27% 15% 6%	17092
	Night	17% 5% 14% 29% 28% 7%	26385

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	23% 9% 3 6% 4 4 4 4 5% 6% 32%	5100
	11th to 20th	Day	17% 5% 2 4 2 3 3 2 3 5% 54%	5340
	21st to end	Day	19% 7% 3 5% 3 4 4 2 5% 6% 42%	5843
February	1st to 10th	Day	23% 7% 2 5% 3 3 3 3 3 6% 41%	1890
	11th to 20th	Day	20% 10% 3 6% 4 3 4 3 5% 6% 36%	1845
	21st to end	Day	20% 10% 2 6% 4 3 3 3 5% 7% 37%	1738
March	1st to 10th	Day	26% 13% 3 5% 3 3 3 2 4 6% 32%	5062
	11th to 20th	Day	21% 7% 2 6% 3 3 3 3 5% 7% 41%	5110
	21st to end	Day	24% 10% 3 7% 4 5% 5% 4 5% 7% 27%	5607
April	1st to 10th	Day	18% 8% 3 6% 4 4 4 4 6% 7% 36%	2385
	11th to 20th	Day	15% 8% 2 6% 3 3 4 3 5% 6% 45%	2369
	21st to end	Day	10% 7% 1 5% 4 3 4 3 5% 9% 50%	2462
May	1st to 10th	Day	5% 5% 1 3 2 2 3 3 4 6% 66%	5880
	11th to 20th	Day	5% 3 1 3 2 2 2 2 4 6% 70%	5883
	21st to end	Day	4 3 1 3 2 2 2 2 4 6% 70%	6902
June	1st to 10th	Day	8% 6% 2 5% 3 2 3 4 5% 7% 54%	2800
	11th to 20th	Day	3 3 1 3 2 2 3 3 4 7% 70%	2800
	21st to end	Day	4 2 1 4 2 2 3 2 3 6% 72%	2800
July	1st to 10th	Day	1 2 1 3 2 1 2 1 2 3 83%	6285
	11th to 20th	Day	1 1 1 3 2 2 2 1 2 4 80%	5880
	21st to end	Day	3 2 4 2 1 2 2 3 5% 75%	6402
August	1st to 10th	Day	1 1 1 3 2 2 3 2 3 5% 76%	5777
	11th to 20th	Day	2 3 1 3 2 1 2 2 3 4 77%	5796
	21st to end	Day	1 2 1 3 2 2 2 2 4 6% 74%	5984
September	1st to 10th	Day	2 2 1 2 2 2 2 2 3 6% 75%	2400
	11th to 20th	Day	4 4 2 5% 2 3 3 3 4 6% 64%	2320
	21st to end	Day	4 3 1 2 1 2 3 2 3 6% 73%	2147
October	1st to 10th	Day	5% 3 1 3 2 2 3 2 4 4 72%	3280
	11th to 20th	Day	9% 4 2 4 2 3 4 3 5% 7% 57%	3261
	21st to end	Day	11% 6% 2 6% 3 3 4 3 5% 7% 48%	3558
November	1st to 10th	Day	14% 5% 2 5% 4 3 4 4 5% 8% 46%	2059
	11th to 20th	Day	18% 7% 2 6% 4 4 3 2 5% 7% 40%	1758
	21st to end	Day	13% 5% 2 4 4 3 4 4 5% 7% 50%	1680
December	1st to 10th	Day	11% 6% 2 4 2 3 4 4 6% 8% 50%	2700
	11th to 20th	Day	31% 9% 2 6% 4 4 4 4 6% 7% 22%	3108
	21st to end	Day	28% 10% 3 7% 6% 4 4 4 5% 6% 23%	4092
January	1st to 10th	Night	27% 9% 2 6% 4 4 4 3 4 6% 30%	7797
	11th to 20th	Night	15% 7% 2 5% 3 3 3 2 3 4 52%	7650
	21st to end	Night	21% 9% 3 7% 4 4 3 3 4 5% 38%	8371
February	1st to 10th	Night	20% 7% 2 6% 4 4 3 4 4 5% 41%	2730
	11th to 20th	Night	18% 11% 4 8% 4 4 4 3 5% 5% 33%	2662
	21st to end	Night	19% 8% 2 5% 3 3 4 3 4 5% 43%	2065
March	1st to 10th	Night	23% 18% 3 6% 3 3 3 3 4 5% 30%	5052
	11th to 20th	Night	21% 9% 2 7% 3 3 3 2 4 5% 40%	5110
	21st to end	Night	23% 14% 4 7% 4 4 4 3 4 6% 28%	5610
April	1st to 10th	Night	17% 10% 3 6% 4 3 3 3 5% 7% 38%	2037
	11th to 20th	Night	12% 10% 2 6% 3 3 3 3 5% 7% 46%	1979
	21st to end	Night	8% 6% 2 5% 4 3 3 3 6% 8% 53%	1934
May	1st to 10th	Night	8% 5% 1 5% 2 2 2 2 3 6% 65%	4100
	11th to 20th	Night	5% 5% 3 6% 4 3 2 2 2 4 64%	4014
	21st to end	Night	3 4 3 5% 3 2 2 3 4 5% 67%	3972
June	1st to 10th	Night	6% 7% 3 6% 3 3 4 3 4 7% 54%	1600
	11th to 20th	Night	3 2 2 3 2 2 2 3 3 6% 72%	1600
	21st to end	Night	4 3 1 4 2 4 3 2 4 3 70%	1600
July	1st to 10th	Night	1 1 1 4 2 2 1 2 3 4 80%	3658
	11th to 20th	Night	1 1 4 8% 4 3 2 2 3 4 70%	4100
	21st to end	Night	7% 7% 9% 5% 4 2 2 4 5% 56%	4472
August	1st to 10th	Night	1 2 2 9% 5% 3 3 3 3 5% 63%	4035
	11th to 20th	Night	2 7% 2 7% 3 2 2 2 3 3 66%	4052
	21st to end	Night	3 2 1 5% 3 3 2 2 3 4 71%	5014
September	1st to 10th	Night	2 3 2 3 3 1 1 1 4 6% 74%	2000
	11th to 20th	Night	5% 7% 3 5% 3 3 4 2 4 7% 58%	2076
	21st to end	Night	4 5% 2 4 2 2 2 3 5% 5% 65%	2252
October	1st to 10th	Night	4 3 1 4 3 2 2 1 3 3 74%	3920
	11th to 20th	Night	8% 11% 3 7% 3 3 3 2 3 6% 51%	3897
	21st to end	Night	11% 5% 2 5% 4 4 4 3 5% 7% 50%	4253
November	1st to 10th	Night	14% 7% 2 6% 4 4 5% 4 6% 6% 41%	2460
	11th to 20th	Night	17% 8% 2 6% 4 4 4 4 6% 7% 37%	2857
	21st to end	Night	15% 6% 1 5% 3 3 4 3 5% 7% 47%	2940
December	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 5% 8% 50%	4700
	11th to 20th	Night	32% 10% 2 6% 4 3 4 3 5% 6% 25%	5316
	21st to end	Night	33% 10% 3 6% 3 3 3 2 3 5% 28%	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	51% 7% 12% 15% 10% 4	5101
	11th to 20th	Day	36% 3 6% 10% 19% 26%	5340
	21st to end	Day	43% 3 6% 18% 14% 15%	5843
February	1st to 10th	Day	46% 4 8% 16% 18% 8%	1890
	11th to 20th	Day	48% 6% 7% 18% 17% 3	1854
	21st to end	Day	47% 4 13% 18% 12% 5%	1738
March	1st to 10th	Day	54% 4 7% 21% 14% 1	5062
	11th to 20th	Day	44% 6% 14% 17% 13% 6%	5110
	21st to end	Day	54% 7% 13% 18% 6% 1	5607
April	1st to 10th	Day	46% 6% 12% 23% 12% 1	2385
	11th to 20th	Day	39% 6% 14% 24% 13% 4	2372
	21st to end	Day	31% 7% 15% 28% 17% 3	2462
May	1st to 10th	Day	18% 7% 12% 24% 30% 10%	5880
	11th to 20th	Day	16% 5% 11% 33% 30% 6%	5886
	21st to end	Day	16% 4 11% 51% 18% 1	6904
June	1st to 10th	Day	28% 8% 11% 28% 22% 4	2800
	11th to 20th	Day	15% 4 11% 27% 35% 9%	2800
	21st to end	Day	15% 2 7% 20% 38% 17%	2800
July	1st to 10th	Day	8% 2 4 14% 25% 48%	6217
	11th to 20th	Day	8% 1 6% 8% 24% 52%	5811
	21st to end	Day	11% 4 9% 17% 32% 27%	6217
August	1st to 10th	Day	12% 2 9% 14% 31% 33%	4206
	11th to 20th	Day	10% 3 6% 22% 38% 21%	4195
	21st to end	Day	12% 2 9% 22% 29% 26%	4311
September	1st to 10th	Day	11% 3 7% 14% 30% 35%	2400
	11th to 20th	Day	20% 3 10% 27% 30% 9%	2320
	21st to end	Day	15% 3 8% 21% 31% 22%	2147
October	1st to 10th	Day	18% 2 4 18% 19% 40%	3280
	11th to 20th	Day	25% 5% 8% 24% 28% 10%	3261
	21st to end	Day	34% 5% 9% 23% 20% 10%	3558
November	1st to 10th	Day	36% 5% 10% 24% 16% 8%	2059
	11th to 20th	Day	44% 5% 12% 18% 14% 8%	1758
	21st to end	Day	34% 6% 11% 17% 21% 11%	1680
December	1st to 10th	Day	32% 4 8% 22% 26% 9%	2700
	11th to 20th	Day	60% 5% 9% 13% 10% 3	3108
	21st to end	Day	60% 7% 9% 16% 7% 2	4092
January	1st to 10th	Night	55% 7% 13% 13% 9% 2	7797
	11th to 20th	Night	37% 4 5% 15% 18% 22%	7650
	21st to end	Night	49% 4 6% 11% 18% 13%	8371
February	1st to 10th	Night	44% 5% 9% 17% 17% 8%	2730
	11th to 20th	Night	51% 5% 8% 18% 13% 4	2664
	21st to end	Night	42% 5% 15% 20% 14% 4	2065
March	1st to 10th	Night	56% 5% 9% 19% 10% 1	5052
	11th to 20th	Night	45% 7% 12% 17% 12% 7%	5110
	21st to end	Night	55% 8% 12% 16% 7% 1	5610
April	1st to 10th	Night	45% 6% 14% 20% 11% 2	2037
	11th to 20th	Night	38% 6% 15% 24% 14% 4	1979
	21st to end	Night	29% 5% 17% 31% 16% 3	1934
May	1st to 10th	Night	21% 4 11% 24% 27% 13%	4097
	11th to 20th	Night	23% 4 10% 27% 27% 9%	4015
	21st to end	Night	18% 5% 12% 44% 21%	3972
June	1st to 10th	Night	29% 7% 11% 30% 21% 3	1600
	11th to 20th	Night	14% 5% 9% 26% 37% 10%	1600
	21st to end	Night	16% 2 10% 17% 35% 20%	1600
July	1st to 10th	Night	9% 2 5% 14% 21% 49%	3618
	11th to 20th	Night	14% 1 11% 6% 22% 47%	4046
	21st to end	Night	23% 5% 11% 10% 23% 26%	4345
August	1st to 10th	Night	16% 2 17% 13% 26% 26%	2929
	11th to 20th	Night	15% 2 12% 18% 31% 21%	2929
	21st to end	Night	14% 2 9% 19% 27% 29%	3607
September	1st to 10th	Night	12% 1 7% 14% 29% 37%	2000
	11th to 20th	Night	25% 3 11% 20% 32% 9%	2076
	21st to end	Night	19% 4 10% 18% 26% 24%	2252
October	1st to 10th	Night	17% 2 6% 14% 21% 41%	3920
	11th to 20th	Night	34% 5% 8% 17% 28% 8%	3897
	21st to end	Night	33% 4 9% 25% 18% 12%	4253
November	1st to 10th	Night	40% 7% 14% 17% 15% 7%	2460
	11th to 20th	Night	43% 7% 13% 17% 15% 5%	2857
	21st to end	Night	37% 6% 11% 17% 19% 11%	2940
December	1st to 10th	Night	33% 4 9% 23% 21% 10%	4700
	11th to 20th	Night	61% 4 6% 14% 11% 4	5316
	21st to end	Night	60% 5% 10% 15% 8% 2	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	38% 11% 22% 18% 9% 1	351
	11th to 20th	Day	27% 10% 21% 24% 14% 5%	430
	21st to end	Day	24% 9% 24% 23% 16% 5%	473
February	1st to 10th	Day	27% 13% 21% 22% 14% 3	430
	11th to 20th	Day	31% 17% 23% 17% 12%	425
	21st to end	Day	27% 14% 26% 22% 8% 2	430
March	1st to 10th	Day	34% 17% 26% 16% 5% 1	540
	11th to 20th	Day	27% 14% 29% 19% 9% 2	540
	21st to end	Day	28% 17% 28% 18% 7% 2	594
April	1st to 10th	Day	26% 18% 30% 17% 9% 1	505
	11th to 20th	Day	25% 15% 30% 19% 9% 3	492
	21st to end	Day	17% 18% 31% 20% 9% 5%	500
May	1st to 10th	Day	16% 16% 29% 26% 10% 3	503
	11th to 20th	Day	20% 15% 28% 21% 11% 5%	528
	21st to end	Day	17% 13% 29% 24% 12% 5%	573
June	1st to 10th	Day	13% 11% 32% 28% 13% 5%	530
	11th to 20th	Day	9% 16% 35% 26% 10% 4	530
	21st to end	Day	5% 8% 28% 35% 17% 7%	530
July	1st to 10th	Day	6% 4 27% 40% 14% 7%	526
	11th to 20th	Day	2 2 25% 40% 21% 9%	524
	21st to end	Day	2 2 19% 44% 23% 9%	575
August	1st to 10th	Day	3 4 28% 38% 18% 9%	527
	11th to 20th	Day	4 5% 25% 36% 22% 8%	517
	21st to end	Day	4 4 25% 38% 21% 8%	583
September	1st to 10th	Day	5% 6% 25% 36% 20% 8%	530
	11th to 20th	Day	7% 8% 26% 34% 19% 6%	530
	21st to end	Day	8% 7% 24% 32% 21% 8%	530
October	1st to 10th	Day	11% 9% 24% 26% 23% 7%	530
	11th to 20th	Day	14% 9% 18% 27% 21% 11%	530
	21st to end	Day	17% 8% 21% 31% 17% 6%	583
November	1st to 10th	Day	17% 10% 24% 23% 21% 5%	535
	11th to 20th	Day	20% 11% 18% 23% 21% 8%	266
	21st to end	Day	17% 5% 25% 22% 22% 8%	220
December	1st to 10th	Day	22% 10% 16% 26% 14% 11%	220
	11th to 20th	Day	32% 12% 17% 19% 11% 9%	220
	21st to end	Day	30% 12% 21% 17% 15% 5%	242
January	1st to 10th	Night	28% 8% 18% 25% 17% 4	840
	11th to 20th	Night	25% 4 16% 30% 19% 6%	840
	21st to end	Night	24% 5% 15% 29% 21% 5%	924
February	1st to 10th	Night	23% 7% 17% 31% 18% 3	840
	11th to 20th	Night	24% 8% 19% 27% 18% 4	824
	21st to end	Night	25% 7% 20% 31% 15% 2	692
March	1st to 10th	Night	30% 9% 17% 28% 13% 3	840
	11th to 20th	Night	28% 6% 12% 30% 20% 3	840
	21st to end	Night	26% 8% 18% 28% 16% 3	924
April	1st to 10th	Night	22% 8% 21% 27% 19% 4	804
	11th to 20th	Night	18% 11% 16% 29% 21% 5%	791
	21st to end	Night	12% 9% 18% 31% 25% 5%	734
May	1st to 10th	Night	10% 7% 21% 28% 26% 7%	600
	11th to 20th	Night	9% 4 17% 30% 35% 6%	571
	21st to end	Night	11% 6% 20% 27% 32% 5%	433
June	1st to 10th	Night	8% 7% 17% 33% 31% 5%	400
	11th to 20th	Night	3 6% 19% 38% 32% 3	400
	21st to end	Night	4 2 8% 38% 43% 5%	400
July	1st to 10th	Night	3 1 9% 29% 49% 10%	395
	11th to 20th	Night	3 3 25% 52% 16%	582
	21st to end	Night	2 3 20% 55% 20%	657
August	1st to 10th	Night	2 2 4 24% 54% 14%	597
	11th to 20th	Night	2 1 4 29% 48% 16%	594
	21st to end	Night	4 2 5% 27% 48% 14%	879
September	1st to 10th	Night	3 2 8% 28% 45% 14%	800
	11th to 20th	Night	8% 3 10% 29% 40% 11%	800
	21st to end	Night	8% 3 10% 30% 35% 14%	800
October	1st to 10th	Night	8% 5% 11% 31% 35% 10%	800
	11th to 20th	Night	13% 3 11% 27% 35% 12%	800
	21st to end	Night	15% 4 12% 29% 29% 11%	880
November	1st to 10th	Night	18% 4 15% 26% 29% 8%	820
	11th to 20th	Night	21% 5% 15% 31% 23% 5%	840
	21st to end	Night	18% 5% 14% 35% 21% 5%	840
December	1st to 10th	Night	24% 4 15% 30% 21% 7%	840
	11th to 20th	Night	32% 7% 13% 27% 16% 4	840
	21st to end	Night	33% 8% 17% 23% 15% 3	924

Page generated at 2026-03-29 23:18:41. Version ac07

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