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 2024-12-02.

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	1 3 1 4 3 3 3 3 5% 7% 66%	105227
	Night	1 3 2 4 3 3 3 3 5% 7% 67%	103118
Transparency	Day	17% 4 9% 18% 27% 25%	104969
	Night	16% 4 10% 22% 29% 19%	102965
Seeing	Day	5% 12% 23% 30% 22% 8%	15209
	Night	3 4 22% 41% 26% 5%	24722

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	3 1 5% 4 4 5% 5% 7% 11% 55%	2539
	11th to 20th	Day	3 2 6% 5% 5% 6% 5% 7% 10% 51%	2554
	21st to end	Day	1 5% 3 7% 5% 5% 5% 5% 8% 11% 46%	3146
February	1st to 10th	Day	1 3 2 5% 4 3 3 2 5% 9% 62%	1843
	11th to 20th	Day	1 3 1 6% 4 4 4 4 6% 10% 56%	1850
	21st to end	Day	3 1 6% 5% 2 3 4 6% 9% 59%	1570
March	1st to 10th	Day	1 3 2 5% 4 5% 5% 5% 8% 11% 51%	3138
	11th to 20th	Day	2 3 6% 3 4 3 4 6% 12% 57%	3294
	21st to end	Day	5% 3 6% 4 4 4 4 6% 9% 55%	4160
April	1st to 10th	Day	2 4 2 5% 3 4 3 4 6% 8% 58%	2280
	11th to 20th	Day	1 4 2 4 4 3 3 4 6% 7% 62%	2249
	21st to end	Day	2 4 2 4 3 3 3 4 6% 7% 64%	2280
May	1st to 10th	Day	1 3 1 3 3 2 3 3 4 6% 70%	4047
	11th to 20th	Day	2 3 1 4 3 3 4 3 4 6% 68%	4071
	21st to end	Day	3 4 2 5% 3 3 3 3 4 5% 64%	4774
June	1st to 10th	Day	3 4 2 5% 4 4 4 3 5% 6% 61%	2660
	11th to 20th	Day	2 2 1 3 2 2 2 3 4 5% 75%	2660
	21st to end	Day	2 3 1 3 3 3 3 2 3 4 73%	2660
July	1st to 10th	Day	1 2 1 3 2 2 3 2 3 3 77%	4420
	11th to 20th	Day	3 4 2 5% 4 4 5% 4 4 6% 60%	4420
	21st to end	Day	3 3 1 4 3 3 4 3 5% 5% 66%	4744
August	1st to 10th	Day	3 3 1 5% 4 3 3 3 4 4 66%	3827
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 3 81%	3724
	21st to end	Day	1 1 1 2 1 2 2 1 2 3 84%	4180
September	1st to 10th	Day	2 2 1 4 2 3 3 2 3 4 75%	2280
	11th to 20th	Day	1 2 1 4 2 3 3 2 3 4 75%	2187
	21st to end	Day	1 1 1 2 1 2 2 2 4 5% 78%	2090
October	1st to 10th	Day	1 3 1 3 2 2 3 3 4 5% 72%	3407
	11th to 20th	Day	2 2 1 2 1 2 2 2 4 4 79%	3161
	21st to end	Day	1 2 1 2 2 2 3 3 4 5% 75%	3292
November	1st to 10th	Day	1 3 1 4 2 3 2 2 5% 8% 68%	1764
	11th to 20th	Day	1 2 1 2 2 3 3 2 5% 9% 71%	1800
	21st to end	Day	1 3 1 4 3 3 3 3 5% 10% 66%	1800
December	1st to 10th	Day	1 3 1 2 3 3 3 4 5% 8% 67%	1634
	11th to 20th	Day	1 4 2 7% 6% 5% 5% 6% 7% 10% 47%	1928
	21st to end	Day	4 3 7% 5% 5% 6% 5% 8% 11% 47%	2794
January	1st to 10th	Night	1 4 3 8% 5% 4 4 3 6% 7% 56%	4406
	11th to 20th	Night	3 2 6% 4 4 5% 5% 7% 11% 52%	4389
	21st to end	Night	2 6% 2 6% 4 5% 5% 4 7% 10% 50%	4521
February	1st to 10th	Night	4 3 5% 4 3 3 3 6% 7% 60%	2336
	11th to 20th	Night	1 4 2 4 3 3 3 3 5% 9% 62%	2218
	21st to end	Night	3 1 6% 3 3 3 3 6% 9% 63%	1884
March	1st to 10th	Night	3 2 6% 5% 5% 5% 4 6% 8% 57%	3736
	11th to 20th	Night	4 2 6% 3 3 4 3 6% 7% 60%	3681
	21st to end	Night	4 2 5% 4 5% 4 3 5% 8% 60%	3491
April	1st to 10th	Night	2 4 2 4 3 3 3 4 5% 6% 65%	1900
	11th to 20th	Night	1 4 1 4 4 2 3 3 4 7% 66%	1879
	21st to end	Night	2 4 2 3 3 2 2 3 4 5% 69%	1900
May	1st to 10th	Night	2 2 3 1 2 2 3 4 6% 74%	2924
	11th to 20th	Night	2 2 1 4 3 3 2 3 4 5% 71%	2834
	21st to end	Night	3 3 1 3 3 3 3 3 4 6% 69%	2799
June	1st to 10th	Night	1 3 1 3 3 3 4 4 7% 6% 65%	1520
	11th to 20th	Night	2 2 1 2 2 2 2 2 4 5% 78%	1520
	21st to end	Night	1 2 1 3 2 2 3 2 3 4 77%	1520
July	1st to 10th	Night	1 1 1 1 2 2 3 4 84%	2540
	11th to 20th	Night	2 3 2 6% 4 4 4 3 6% 6% 59%	2540
	21st to end	Night	1 2 1 3 3 3 3 3 4 6% 72%	2792
August	1st to 10th	Night	2 2 1 3 3 3 3 2 5% 5% 71%	3119
	11th to 20th	Night	1 1 1 2 2 2 2 2 3 3 82%	3126
	21st to end	Night	1 1 2 1 1 1 2 2 3 85%	3498
September	1st to 10th	Night	1 2 1 2 1 1 2 2 3 4 82%	1900
	11th to 20th	Night	2 2 1 3 2 2 2 1 3 5% 77%	1991
	21st to end	Night	1 1 1 2 1 1 2 2 2 4 83%	2090
October	1st to 10th	Night	2 2 1 3 2 2 2 2 3 5% 76%	3569
	11th to 20th	Night	1 2 1 2 1 1 2 2 3 5% 81%	3777
	21st to end	Night	1 2 1 2 2 2 2 1 4 5% 77%	4270
November	1st to 10th	Night	1 2 1 3 2 2 2 3 4 6% 74%	2535
	11th to 20th	Night	2 1 3 2 2 4 3 5% 7% 71%	2600
	21st to end	Night	1 3 2 4 2 3 3 3 4 7% 69%	2600
December	1st to 10th	Night	1 2 2 5% 3 3 3 3 6% 9% 63%	2575
	11th to 20th	Night	1 4 3 6% 4 5% 4 5% 8% 10% 49%	3276
	21st to end	Night	1 4 3 8% 6% 6% 6% 6% 8% 10% 44%	4862

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	17% 6% 18% 31% 25% 3	2539
	11th to 20th	Day	21% 9% 18% 21% 24% 6%	2554
	21st to end	Day	26% 7% 17% 24% 21% 5%	3146
February	1st to 10th	Day	19% 4 14% 25% 27% 12%	1843
	11th to 20th	Day	22% 5% 10% 25% 29% 10%	1860
	21st to end	Day	20% 5% 14% 28% 25% 8%	1570
March	1st to 10th	Day	20% 6% 14% 29% 23% 8%	3138
	11th to 20th	Day	16% 4 19% 37% 19% 5%	3294
	21st to end	Day	22% 5% 18% 27% 25% 4	4160
April	1st to 10th	Day	22% 5% 14% 27% 21% 11%	2280
	11th to 20th	Day	19% 5% 12% 27% 28% 11%	2252
	21st to end	Day	18% 4 13% 29% 28% 7%	2280
May	1st to 10th	Day	14% 3 10% 21% 37% 16%	4047
	11th to 20th	Day	16% 3 9% 18% 36% 17%	4074
	21st to end	Day	18% 3 11% 18% 40% 10%	4774
June	1st to 10th	Day	23% 4 8% 17% 31% 16%	2660
	11th to 20th	Day	13% 3 5% 14% 34% 31%	2660
	21st to end	Day	15% 2 3 9% 28% 42%	2660
July	1st to 10th	Day	12% 2 2 5% 12% 68%	4351
	11th to 20th	Day	23% 4 4 7% 16% 47%	4345
	21st to end	Day	18% 4 5% 11% 16% 46%	4594
August	1st to 10th	Day	20% 3 3 8% 23% 42%	3812
	11th to 20th	Day	10% 2 3 5% 15% 66%	3760
	21st to end	Day	9% 1 2 4 28% 55%	4179
September	1st to 10th	Day	14% 3 4 7% 23% 49%	2280
	11th to 20th	Day	15% 1 4 13% 31% 36%	2187
	21st to end	Day	10% 2 4 15% 35% 35%	2090
October	1st to 10th	Day	14% 2 3 11% 35% 34%	3407
	11th to 20th	Day	10% 2 3 11% 41% 33%	3161
	21st to end	Day	10% 2 3 18% 46% 20%	3292
November	1st to 10th	Day	15% 2 10% 24% 33% 16%	1764
	11th to 20th	Day	10% 3 10% 26% 37% 14%	1800
	21st to end	Day	15% 4 11% 26% 29% 15%	1800
December	1st to 10th	Day	14% 7% 12% 28% 27% 11%	1634
	11th to 20th	Day	27% 9% 14% 24% 18% 8%	1928
	21st to end	Day	27% 7% 16% 22% 22% 5%	2794
January	1st to 10th	Night	20% 5% 18% 29% 24% 4	4406
	11th to 20th	Night	19% 7% 19% 31% 18% 6%	4389
	21st to end	Night	25% 8% 15% 28% 18% 5%	4521
February	1st to 10th	Night	20% 6% 12% 27% 23% 12%	2336
	11th to 20th	Night	17% 5% 10% 27% 31% 10%	2219
	21st to end	Night	18% 4 14% 30% 26% 7%	1884
March	1st to 10th	Night	21% 6% 13% 27% 26% 8%	3736
	11th to 20th	Night	16% 5% 18% 33% 24% 4	3681
	21st to end	Night	20% 3 16% 30% 28% 3	3491
April	1st to 10th	Night	20% 5% 14% 31% 23% 7%	1900
	11th to 20th	Night	17% 4 13% 31% 25% 10%	1879
	21st to end	Night	16% 4 13% 37% 24% 5%	1900
May	1st to 10th	Night	11% 4 8% 28% 40% 9%	2924
	11th to 20th	Night	14% 4 9% 24% 38% 11%	2835
	21st to end	Night	15% 3 11% 22% 44% 5%	2799
June	1st to 10th	Night	16% 5% 11% 22% 34% 13%	1520
	11th to 20th	Night	10% 3 6% 17% 39% 25%	1520
	21st to end	Night	11% 3 4 13% 30% 39%	1520
July	1st to 10th	Night	5% 2 3 7% 15% 69%	2500
	11th to 20th	Night	23% 4 4 8% 20% 41%	2492
	21st to end	Night	12% 3 6% 15% 19% 45%	2704
August	1st to 10th	Night	14% 3 4 11% 28% 40%	3110
	11th to 20th	Night	9% 2 4 6% 17% 62%	3156
	21st to end	Night	7% 1 3 8% 30% 50%	3498
September	1st to 10th	Night	8% 2 4 10% 31% 46%	1900
	11th to 20th	Night	11% 1 7% 15% 35% 31%	1991
	21st to end	Night	8% 2 4 17% 37% 32%	2090
October	1st to 10th	Night	12% 3 4 12% 39% 30%	3569
	11th to 20th	Night	8% 2 3 14% 46% 26%	3777
	21st to end	Night	11% 2 4 15% 43% 25%	4270
November	1st to 10th	Night	11% 3 11% 26% 35% 14%	2535
	11th to 20th	Night	12% 3 12% 27% 34% 12%	2600
	21st to end	Night	15% 4 11% 25% 32% 13%	2600
December	1st to 10th	Night	18% 6% 14% 26% 25% 11%	2575
	11th to 20th	Night	22% 9% 17% 25% 22% 6%	3276
	21st to end	Night	29% 9% 14% 20% 24% 4	4862

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 17% 30% 34% 13% 3	180
	11th to 20th	Day	1 12% 27% 31% 19% 10%	194
	21st to end	Day	4 10% 19% 36% 24% 7%	407
February	1st to 10th	Day	2 9% 30% 32% 19% 8%	433
	11th to 20th	Day	2 11% 25% 40% 18% 5%	455
	21st to end	Day	3 14% 28% 32% 19% 3	382
March	1st to 10th	Day	6% 13% 28% 33% 16% 4	460
	11th to 20th	Day	3 15% 30% 28% 16% 7%	460
	21st to end	Day	5% 18% 30% 32% 14% 1	506
April	1st to 10th	Day	6% 16% 26% 28% 18% 5%	460
	11th to 20th	Day	8% 19% 23% 29% 16% 5%	452
	21st to end	Day	7% 18% 24% 27% 16% 8%	460
May	1st to 10th	Day	9% 16% 31% 26% 13% 6%	463
	11th to 20th	Day	9% 17% 24% 24% 17% 9%	488
	21st to end	Day	12% 12% 20% 25% 21% 10%	529
June	1st to 10th	Day	7% 13% 22% 26% 23% 9%	490
	11th to 20th	Day	5% 17% 24% 28% 19% 7%	490
	21st to end	Day	3 11% 26% 31% 22% 7%	490
July	1st to 10th	Day	5% 6% 20% 30% 29% 10%	486
	11th to 20th	Day	5% 5% 18% 30% 31% 12%	484
	21st to end	Day	8% 4 18% 31% 29% 11%	531
August	1st to 10th	Day	7% 7% 21% 29% 29% 8%	487
	11th to 20th	Day	5% 6% 22% 28% 27% 12%	477
	21st to end	Day	5% 5% 18% 29% 31% 12%	539
September	1st to 10th	Day	5% 6% 20% 32% 26% 11%	490
	11th to 20th	Day	4 12% 23% 33% 24% 5%	490
	21st to end	Day	4 10% 20% 32% 29% 6%	490
October	1st to 10th	Day	5% 12% 23% 30% 21% 9%	490
	11th to 20th	Day	4 12% 22% 33% 21% 8%	490
	21st to end	Day	4 11% 22% 29% 23% 10%	445
November	1st to 10th	Day	4 10% 21% 30% 22% 12%	300
	11th to 20th	Day	2 11% 23% 29% 22% 13%	300
	21st to end	Day	4 9% 19% 31% 29% 7%	300
December	1st to 10th	Day	4 8% 22% 36% 20% 10%	233
	11th to 20th	Day	2 13% 21% 37% 17% 10%	180
	21st to end	Day	7% 15% 23% 28% 22% 5%	198
January	1st to 10th	Night	4 4 27% 34% 21% 8%	760
	11th to 20th	Night	2 3 27% 41% 21% 6%	760
	21st to end	Night	4 4 25% 41% 19% 6%	836
February	1st to 10th	Night	2 4 28% 39% 23% 5%	760
	11th to 20th	Night	2 6% 27% 40% 21% 5%	744
	21st to end	Night	2 5% 32% 42% 15% 4	628
March	1st to 10th	Night	3 7% 26% 45% 14% 5%	760
	11th to 20th	Night	2 6% 27% 39% 20% 7%	760
	21st to end	Night	3 7% 31% 42% 16% 2	836
April	1st to 10th	Night	4 6% 29% 39% 20% 3	760
	11th to 20th	Night	3 8% 29% 38% 19% 5%	751
	21st to end	Night	3 7% 27% 36% 22% 5%	760
May	1st to 10th	Night	6% 4 29% 41% 18% 2	608
	11th to 20th	Night	5% 6% 24% 40% 24% 1	561
	21st to end	Night	8% 5% 19% 37% 28% 3	436
June	1st to 10th	Night	2 4 17% 45% 30% 2	380
	11th to 20th	Night	2 4 17% 49% 27% 1	380
	21st to end	Night	1 2 15% 54% 27% 1	380
July	1st to 10th	Night	1 5% 51% 41% 2	370
	11th to 20th	Night	2 1 7% 48% 40% 2	368
	21st to end	Night	3 3 45% 46% 3	435
August	1st to 10th	Night	4 1 13% 41% 35% 5%	721
	11th to 20th	Night	3 2 14% 42% 35% 4	752
	21st to end	Night	3 2 11% 41% 38% 4	836
September	1st to 10th	Night	2 2 12% 39% 40% 5%	760
	11th to 20th	Night	3 2 16% 41% 32% 6%	760
	21st to end	Night	2 3 16% 38% 33% 9%	760
October	1st to 10th	Night	3 2 18% 40% 29% 7%	760
	11th to 20th	Night	3 4 16% 41% 30% 6%	760
	21st to end	Night	3 3 20% 36% 28% 10%	836
November	1st to 10th	Night	1 4 21% 37% 30% 8%	780
	11th to 20th	Night	2 3 23% 45% 22% 5%	800
	21st to end	Night	4 4 23% 40% 26% 5%	800
December	1st to 10th	Night	2 3 27% 43% 18% 6%	768
	11th to 20th	Night	3 3 29% 43% 19% 4	760
	21st to end	Night	2 5% 32% 39% 18% 3	836

Page generated at 2024-11-29 07:43:06. Version ac07

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