McGee Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McGee Creek clear sky chart from 2005-11-06 to 2026-03-03.

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	1 3 1 4 3 3 3 3 5% 7% 67%	139456
	Night	1 3 1 4 3 3 3 3 5% 7% 68%	139141
Transparency	Day	16% 4 8% 18% 29% 26%	134494
	Night	15% 4 10% 21% 30% 20%	135078
Seeing	Day	6% 12% 24% 30% 21% 8%	16780
	Night	3 4 23% 41% 25% 5%	26380

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	2 1 3 3 3 4 4 6% 10% 63%	4722
	11th to 20th	Day	2 1 3 3 3 4 3 4 6% 72%	4782
	21st to end	Day	1 4 3 6% 4 4 4 4 6% 10% 54%	5843
February	1st to 10th	Day	1 3 2 5% 4 3 3 2 5% 9% 63%	2037
	11th to 20th	Day	1 3 1 5% 4 4 5% 4 6% 10% 56%	2050
	21st to end	Day	3 1 6% 4 2 3 4 6% 10% 60%	1730
March	1st to 10th	Day	1 4 2 6% 4 5% 5% 5% 8% 10% 50%	4539
	11th to 20th	Day	2 2 5% 3 4 4 4 6% 12% 58%	4726
	21st to end	Day	4 2 5% 4 3 4 3 5% 9% 61%	5964
April	1st to 10th	Day	2 4 2 5% 3 4 3 4 7% 8% 58%	2400
	11th to 20th	Day	1 4 2 4 4 3 3 4 6% 7% 63%	2369
	21st to end	Day	2 4 2 4 3 3 4 4 6% 7% 62%	2400
May	1st to 10th	Day	2 3 1 4 3 2 3 3 4 6% 69%	5791
	11th to 20th	Day	2 3 1 4 3 3 3 2 4 5% 69%	5841
	21st to end	Day	2 3 1 4 3 3 3 3 4 5% 68%	6850
June	1st to 10th	Day	3 4 2 5% 4 4 4 3 5% 6% 61%	2800
	11th to 20th	Day	1 2 1 3 2 2 2 3 4 5% 76%	2800
	21st to end	Day	2 3 1 3 3 3 3 2 3 4 73%	2800
July	1st to 10th	Day	1 1 1 3 2 2 2 2 3 3 81%	6319
	11th to 20th	Day	2 3 1 4 3 4 4 4 4 5% 64%	6320
	21st to end	Day	2 2 1 3 3 3 4 3 5% 6% 68%	6821
August	1st to 10th	Day	2 2 1 3 3 3 3 2 3 3 75%	5416
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 3 81%	5364
	21st to end	Day	2 2 1 4 3 3 3 2 3 4 73%	5984
September	1st to 10th	Day	2 2 1 4 2 3 3 2 3 4 75%	2400
	11th to 20th	Day	2 3 1 4 2 3 3 2 3 4 74%	2302
	21st to end	Day	1 1 1 2 1 2 2 2 4 5% 78%	2200
October	1st to 10th	Day	1 3 1 3 2 2 3 3 4 5% 73%	3514
	11th to 20th	Day	2 2 1 2 1 2 2 2 4 4 79%	3261
	21st to end	Day	1 2 1 2 2 2 3 3 4 5% 75%	3397
November	1st to 10th	Day	1 3 1 3 2 3 2 2 5% 7% 69%	1854
	11th to 20th	Day	1 3 1 2 2 3 3 2 5% 8% 69%	1890
	21st to end	Day	1 3 1 3 3 3 3 3 5% 10% 65%	1890
December	1st to 10th	Day	1 2 1 2 2 3 2 3 5% 7% 73%	2880
	11th to 20th	Day	1 3 1 5% 4 4 4 5% 6% 9% 60%	3108
	21st to end	Day	4 2 6% 4 4 5% 4 7% 12% 52%	4092
January	1st to 10th	Night	2 2 6% 3 3 3 3 5% 8% 65%	8172
	11th to 20th	Night	2 1 4 2 2 3 3 5% 8% 71%	8163
	21st to end	Night	1 5% 3 6% 4 4 4 4 6% 8% 56%	8371
February	1st to 10th	Night	4 2 5% 4 3 3 3 6% 7% 61%	2581
	11th to 20th	Night	1 4 2 4 3 3 3 4 6% 9% 61%	2458
	21st to end	Night	3 1 5% 3 3 3 3 6% 9% 64%	2076
March	1st to 10th	Night	3 2 6% 5% 5% 5% 3 6% 9% 56%	5400
	11th to 20th	Night	3 2 5% 3 3 4 4 5% 7% 63%	5269
	21st to end	Night	3 1 5% 4 4 4 3 5% 7% 62%	5009
April	1st to 10th	Night	2 4 2 4 3 3 3 3 5% 6% 65%	2000
	11th to 20th	Night	1 4 1 4 4 2 3 3 4 7% 66%	1979
	21st to end	Night	2 4 2 3 3 3 3 3 4 6% 67%	2000
May	1st to 10th	Night	3 3 1 3 2 2 2 2 4 6% 72%	4192
	11th to 20th	Night	1 2 1 4 3 3 2 3 4 5% 71%	4074
	21st to end	Night	2 3 1 3 2 2 2 2 3 6% 73%	4023
June	1st to 10th	Night	1 3 1 3 3 4 4 4 7% 6% 65%	1600
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 5% 79%	1600
	21st to end	Night	1 2 1 2 2 2 3 2 3 4 78%	1600
July	1st to 10th	Night	1 1 1 1 2 3 4 87%	3640
	11th to 20th	Night	1 3 2 5% 3 3 4 3 5% 6% 64%	3640
	21st to end	Night	1 1 1 2 2 2 3 2 3 6% 78%	4015
August	1st to 10th	Night	1 1 1 2 2 2 2 2 4 4 79%	4411
	11th to 20th	Night	1 1 1 2 2 2 3 2 3 4 79%	4506
	21st to end	Night	2 3 1 3 2 2 2 2 4 5% 75%	5015
September	1st to 10th	Night	1 2 1 2 2 1 2 2 3 4 80%	2000
	11th to 20th	Night	2 2 1 3 2 2 2 2 4 5% 76%	2096
	21st to end	Night	1 1 1 2 1 1 2 2 2 4 82%	2200
October	1st to 10th	Night	2 2 1 3 2 2 2 2 3 5% 76%	3681
	11th to 20th	Night	1 2 1 2 1 1 2 2 3 5% 81%	3897
	21st to end	Night	1 2 1 2 2 2 2 1 4 5% 77%	4407
November	1st to 10th	Night	1 2 1 3 2 2 2 2 4 6% 75%	2665
	11th to 20th	Night	1 3 1 3 2 2 4 3 5% 7% 69%	2730
	21st to end	Night	1 3 2 3 2 3 3 3 4 7% 69%	2730
December	1st to 10th	Night	1 1 1 3 2 3 3 3 5% 7% 71%	4519
	11th to 20th	Night	1 3 2 4 3 4 4 4 8% 12% 55%	5316
	21st to end	Night	3 2 7% 5% 6% 6% 6% 9% 12% 44%	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	12% 6% 16% 32% 30% 4	4723
	11th to 20th	Day	12% 5% 10% 13% 29% 32%	4782
	21st to end	Day	23% 5% 11% 19% 28% 14%	5843
February	1st to 10th	Day	18% 4 13% 24% 27% 14%	2037
	11th to 20th	Day	21% 5% 9% 24% 30% 10%	2060
	21st to end	Day	19% 5% 16% 27% 24% 9%	1730
March	1st to 10th	Day	22% 6% 10% 22% 30% 10%	4539
	11th to 20th	Day	14% 5% 14% 36% 24% 7%	4726
	21st to end	Day	18% 5% 15% 27% 28% 7%	5964
April	1st to 10th	Day	22% 5% 14% 27% 21% 11%	2400
	11th to 20th	Day	18% 5% 11% 26% 28% 12%	2372
	21st to end	Day	19% 4 13% 29% 28% 7%	2400
May	1st to 10th	Day	16% 3 8% 22% 37% 14%	5791
	11th to 20th	Day	16% 3 7% 19% 39% 16%	5844
	21st to end	Day	16% 3 8% 14% 44% 14%	6851
June	1st to 10th	Day	23% 4 8% 18% 31% 16%	2800
	11th to 20th	Day	12% 3 5% 13% 33% 34%	2800
	21st to end	Day	15% 2 3 8% 28% 43%	2800
July	1st to 10th	Day	10% 1 2 4 11% 72%	6251
	11th to 20th	Day	19% 3 3 6% 14% 55%	6245
	21st to end	Day	15% 3 4 11% 24% 44%	6623
August	1st to 10th	Day	19% 3 3 8% 23% 43%	3934
	11th to 20th	Day	10% 2 3 5% 16% 66%	3880
	21st to end	Day	9% 1 3 5% 29% 54%	4311
September	1st to 10th	Day	14% 3 4 8% 23% 48%	2400
	11th to 20th	Day	16% 1 4 13% 32% 35%	2302
	21st to end	Day	10% 2 3 15% 35% 34%	2200
October	1st to 10th	Day	14% 2 3 12% 35% 35%	3514
	11th to 20th	Day	10% 2 3 11% 41% 33%	3261
	21st to end	Day	10% 2 3 18% 46% 20%	3397
November	1st to 10th	Day	14% 2 10% 25% 33% 16%	1854
	11th to 20th	Day	13% 4 10% 25% 36% 13%	1890
	21st to end	Day	15% 4 11% 27% 30% 14%	1890
December	1st to 10th	Day	11% 5% 7% 29% 31% 16%	2880
	11th to 20th	Day	18% 7% 15% 26% 26% 9%	3108
	21st to end	Day	21% 7% 17% 29% 21% 6%	4092
January	1st to 10th	Night	15% 4 17% 30% 29% 5%	8172
	11th to 20th	Night	11% 4 10% 19% 32% 24%	8163
	21st to end	Night	24% 5% 9% 23% 27% 13%	8371
February	1st to 10th	Night	19% 6% 12% 26% 23% 14%	2581
	11th to 20th	Night	17% 5% 10% 27% 31% 10%	2459
	21st to end	Night	17% 4 15% 30% 25% 9%	2076
March	1st to 10th	Night	22% 6% 9% 22% 31% 10%	5400
	11th to 20th	Night	14% 5% 13% 37% 27% 4	5269
	21st to end	Night	20% 3 17% 30% 26% 4	5009
April	1st to 10th	Night	19% 4 14% 30% 25% 7%	2000
	11th to 20th	Night	16% 4 12% 30% 26% 10%	1979
	21st to end	Night	17% 4 13% 37% 24% 5%	2000
May	1st to 10th	Night	14% 4 7% 31% 37% 7%	4189
	11th to 20th	Night	14% 4 10% 24% 40% 9%	4075
	21st to end	Night	12% 3 8% 17% 51% 9%	4023
June	1st to 10th	Night	16% 5% 10% 24% 33% 12%	1600
	11th to 20th	Night	9% 3 6% 16% 37% 28%	1600
	21st to end	Night	11% 2 4 12% 31% 39%	1600
July	1st to 10th	Night	4 1 2 6% 13% 73%	3600
	11th to 20th	Night	19% 3 3 6% 19% 50%	3592
	21st to end	Night	9% 2 4 13% 29% 43%	3901
August	1st to 10th	Night	13% 3 4 11% 29% 40%	3208
	11th to 20th	Night	9% 2 4 6% 18% 62%	3256
	21st to end	Night	8% 1 3 9% 31% 49%	3608
September	1st to 10th	Night	9% 2 4 11% 30% 44%	2000
	11th to 20th	Night	12% 2 7% 16% 36% 29%	2096
	21st to end	Night	9% 2 4 18% 37% 31%	2200
October	1st to 10th	Night	12% 3 4 12% 39% 30%	3681
	11th to 20th	Night	8% 2 3 14% 46% 26%	3897
	21st to end	Night	11% 2 4 15% 44% 24%	4407
November	1st to 10th	Night	10% 3 11% 27% 35% 15%	2665
	11th to 20th	Night	13% 3 11% 28% 33% 11%	2730
	21st to end	Night	15% 4 10% 26% 33% 12%	2730
December	1st to 10th	Night	13% 4 9% 29% 28% 17%	4519
	11th to 20th	Night	16% 7% 18% 27% 26% 6%	5316
	21st to end	Night	25% 8% 17% 21% 22% 7%	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	3 16% 32% 33% 13% 4	220
	11th to 20th	Day	1 11% 28% 31% 19% 10%	236
	21st to end	Day	4 9% 21% 35% 24% 7%	473
February	1st to 10th	Day	6% 9% 28% 32% 19% 7%	507
	11th to 20th	Day	3 12% 29% 36% 16% 5%	535
	21st to end	Day	3 13% 30% 34% 17% 3	446
March	1st to 10th	Day	6% 14% 29% 32% 15% 3	509
	11th to 20th	Day	4 17% 30% 26% 15% 7%	500
	21st to end	Day	7% 18% 29% 32% 14% 1	550
April	1st to 10th	Day	6% 17% 26% 29% 17% 5%	500
	11th to 20th	Day	8% 19% 25% 28% 16% 5%	492
	21st to end	Day	7% 18% 24% 27% 16% 8%	500
May	1st to 10th	Day	10% 15% 30% 26% 13% 6%	503
	11th to 20th	Day	10% 18% 24% 23% 16% 9%	528
	21st to end	Day	11% 12% 21% 27% 20% 9%	573
June	1st to 10th	Day	7% 12% 21% 27% 23% 9%	530
	11th to 20th	Day	6% 17% 25% 28% 18% 6%	530
	21st to end	Day	3 12% 25% 32% 22% 7%	530
July	1st to 10th	Day	5% 8% 21% 29% 28% 9%	526
	11th to 20th	Day	5% 5% 17% 32% 30% 12%	524
	21st to end	Day	7% 4 18% 32% 29% 10%	575
August	1st to 10th	Day	7% 8% 20% 29% 28% 8%	527
	11th to 20th	Day	4 6% 22% 29% 26% 12%	517
	21st to end	Day	5% 5% 18% 30% 30% 12%	583
September	1st to 10th	Day	5% 7% 20% 32% 25% 11%	530
	11th to 20th	Day	5% 11% 23% 33% 24% 5%	530
	21st to end	Day	4 10% 21% 32% 28% 5%	530
October	1st to 10th	Day	5% 13% 23% 31% 20% 8%	530
	11th to 20th	Day	5% 12% 22% 32% 21% 8%	530
	21st to end	Day	5% 11% 22% 29% 24% 9%	484
November	1st to 10th	Day	5% 9% 22% 30% 23% 12%	330
	11th to 20th	Day	4 12% 23% 28% 21% 12%	330
	21st to end	Day	4 8% 19% 33% 29% 7%	330
December	1st to 10th	Day	4 7% 23% 34% 21% 12%	280
	11th to 20th	Day	3 12% 21% 36% 17% 11%	220
	21st to end	Day	9% 15% 24% 28% 20% 4	242
January	1st to 10th	Night	4 5% 32% 33% 19% 8%	840
	11th to 20th	Night	2 3 28% 42% 21% 5%	840
	21st to end	Night	4 4 26% 42% 19% 6%	924
February	1st to 10th	Night	3 4 29% 39% 21% 4	840
	11th to 20th	Night	2 7% 31% 38% 19% 4	824
	21st to end	Night	1 5% 33% 43% 14% 4	692
March	1st to 10th	Night	3 7% 28% 43% 14% 5%	808
	11th to 20th	Night	2 7% 29% 37% 19% 7%	800
	21st to end	Night	3 8% 31% 41% 15% 2	880
April	1st to 10th	Night	4 6% 30% 40% 19% 3	800
	11th to 20th	Night	3 8% 29% 38% 18% 4	791
	21st to end	Night	3 7% 27% 37% 21% 5%	800
May	1st to 10th	Night	7% 4 29% 40% 18% 2	640
	11th to 20th	Night	5% 7% 25% 39% 23% 1	591
	21st to end	Night	8% 5% 20% 38% 26% 3	459
June	1st to 10th	Night	2 4 16% 47% 30% 2	400
	11th to 20th	Night	2 4 20% 48% 26% 1	400
	21st to end	Night	1 2 15% 55% 26% 1	400
July	1st to 10th	Night	1 7% 51% 38% 2	390
	11th to 20th	Night	2 1 7% 50% 38% 2	388
	21st to end	Night	3 5% 46% 44% 3	458
August	1st to 10th	Night	4 2 14% 41% 34% 5%	759
	11th to 20th	Night	3 2 15% 42% 35% 4	792
	21st to end	Night	3 2 11% 42% 38% 4	880
September	1st to 10th	Night	2 2 12% 39% 39% 5%	800
	11th to 20th	Night	3 3 16% 42% 31% 6%	800
	21st to end	Night	2 3 16% 39% 32% 8%	800
October	1st to 10th	Night	3 3 20% 40% 29% 6%	800
	11th to 20th	Night	3 4 18% 41% 29% 6%	800
	21st to end	Night	3 3 20% 36% 28% 10%	880
November	1st to 10th	Night	1 4 21% 36% 30% 8%	820
	11th to 20th	Night	2 3 24% 44% 21% 5%	840
	21st to end	Night	4 3 24% 40% 25% 4	840
December	1st to 10th	Night	2 3 29% 43% 18% 6%	840
	11th to 20th	Night	3 3 30% 42% 19% 3	840
	21st to end	Night	2 7% 35% 37% 16% 3	924

Page generated at 2026-02-27 22:40:23. Version ac07

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