Whiskeytown National Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiskeytown National Recreation Area clear sky chart from 2005-11-06 to 2024-11-12.

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	10% 4 1 3 2 2 2 2 4 5% 64%	105336
	Night	12% 4 1 3 2 2 3 2 4 5% 60%	102582
Transparency	Day	23% 3 7% 18% 24% 24%	105091
	Night	27% 3 9% 19% 23% 19%	102416
Seeing	Day	13% 10% 25% 31% 18% 5%	15121
	Night	14% 6% 22% 34% 22% 2	24258

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% 7% 2 5% 3 4 4 3 4 7% 38%	2539
	11th to 20th	Day	29% 11% 3 6% 3 3 2 2 2 4 35%	2800
	21st to end	Day	30% 7% 2 5% 3 3 3 3 4 6% 35%	3146
February	1st to 10th	Day	19% 6% 1 4 4 4 4 4 5% 6% 44%	1710
	11th to 20th	Day	17% 6% 1 4 3 2 3 3 4 6% 49%	1669
	21st to end	Day	17% 5% 2 5% 4 3 4 3 5% 8% 45%	1570
March	1st to 10th	Day	25% 13% 3 7% 4 3 4 3 3 5% 30%	3370
	11th to 20th	Day	14% 6% 1 4 2 2 3 2 4 6% 58%	3490
	21st to end	Day	24% 7% 2 6% 4 3 3 3 5% 7% 35%	3877
April	1st to 10th	Day	17% 6% 2 5% 3 4 3 3 6% 6% 44%	2280
	11th to 20th	Day	13% 4 2 4 4 3 3 3 5% 6% 54%	2249
	21st to end	Day	5% 4 1 5% 3 3 3 3 4 7% 62%	2304
May	1st to 10th	Day	6% 4 1 3 3 2 2 2 4 5% 68%	4110
	11th to 20th	Day	4 2 1 2 2 2 2 1 3 5% 76%	4346
	21st to end	Day	5% 2 1 2 2 2 2 2 5% 7% 71%	4813
June	1st to 10th	Day	6% 3 1 3 3 3 4 3 6% 7% 61%	2660
	11th to 20th	Day	3 2 2 2 2 2 2 4 6% 77%	2660
	21st to end	Day	4 2 1 2 1 1 2 2 3 3 80%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 91%	4420
	11th to 20th	Day	2 2 1 2 1 2 1 2 2 3 84%	4400
	21st to end	Day	1 1 1 1 1 2 3 90%	4455
August	1st to 10th	Day	2 1 1 2 2 1 2 2 4 5% 79%	4091
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 88%	3974
	21st to end	Day	1 1 1 1 1 1 2 1 2 4 85%	4180
September	1st to 10th	Day	1 1 1 1 1 1 2 4 88%	2280
	11th to 20th	Day	3 2 2 1 2 2 3 4 5% 73%	2280
	21st to end	Day	3 2 1 2 1 2 2 2 3 5% 78%	2000
October	1st to 10th	Day	3 1 2 1 1 2 2 3 4 80%	3180
	11th to 20th	Day	5% 2 1 2 1 2 2 4 5% 8% 68%	3161
	21st to end	Day	9% 3 2 5% 4 3 4 3 5% 7% 55%	3448
November	1st to 10th	Day	13% 4 2 4 3 4 3 4 5% 6% 52%	1842
	11th to 20th	Day	14% 5% 1 4 2 2 4 3 6% 9% 48%	1610
	21st to end	Day	12% 4 1 3 4 4 3 2 5% 7% 55%	1520
December	1st to 10th	Day	22% 5% 2 3 2 2 3 2 4 6% 48%	1520
	11th to 20th	Day	34% 6% 2 5% 3 3 4 3 4 6% 31%	1928
	21st to end	Day	29% 5% 2 4 3 3 4 3 5% 5% 37%	2794
January	1st to 10th	Night	22% 6% 2 5% 3 3 4 4 6% 7% 38%	4406
	11th to 20th	Night	27% 9% 2 6% 3 3 3 3 4 5% 35%	4163
	21st to end	Night	27% 9% 3 6% 4 4 4 3 4 5% 31%	4521
February	1st to 10th	Night	20% 5% 1 4 3 3 3 3 5% 6% 47%	2470
	11th to 20th	Night	19% 6% 1 4 3 3 4 3 4 6% 47%	2397
	21st to end	Night	15% 5% 2 5% 5% 4 4 3 4 6% 49%	1884
March	1st to 10th	Night	23% 9% 2 5% 3 4 4 3 4 6% 37%	3502
	11th to 20th	Night	16% 5% 1 3 2 2 2 2 4 5% 57%	3490
	21st to end	Night	16% 6% 2 6% 4 4 4 4 5% 8% 40%	3774
April	1st to 10th	Night	15% 6% 3 5% 4 4 4 2 5% 7% 47%	1900
	11th to 20th	Night	10% 4 2 4 3 3 3 4 5% 6% 56%	1879
	21st to end	Night	7% 4 1 3 2 2 2 3 5% 7% 62%	1872
May	1st to 10th	Night	6% 3 2 3 2 2 2 2 3 5% 72%	2860
	11th to 20th	Night	4 2 1 2 1 2 2 2 3 5% 76%	2548
	21st to end	Night	4 2 1 2 2 2 2 2 4 5% 74%	2762
June	1st to 10th	Night	6% 4 1 4 3 2 3 4 7% 6% 60%	1520
	11th to 20th	Night	4 2 1 2 1 1 2 1 4 5% 78%	1520
	21st to end	Night	3 2 2 1 1 2 1 3 3 82%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 2 91%	2540
	11th to 20th	Night	1 1 1 2 2 1 2 2 2 3 83%	2558
	21st to end	Night	1 1 1 1 1 1 3 91%	3109
August	1st to 10th	Night	3 2 1 2 1 1 2 2 3 3 80%	2848
	11th to 20th	Night	1 1 1 1 2 1 2 2 89%	2865
	21st to end	Night	5% 1 1 1 1 1 1 1 2 86%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 89%	1900
	11th to 20th	Night	3 1 1 2 2 2 2 3 6% 77%	1900
	21st to end	Night	2 2 1 2 2 1 2 2 3 5% 77%	2176
October	1st to 10th	Night	3 2 1 2 2 3 2 3 3 80%	3800
	11th to 20th	Night	5% 2 1 2 2 2 2 2 3 6% 73%	3777
	21st to end	Night	8% 2 1 3 2 2 3 3 6% 8% 63%	4121
November	1st to 10th	Night	12% 4 1 4 3 2 4 3 6% 7% 53%	2454
	11th to 20th	Night	14% 4 2 4 3 3 4 4 6% 9% 48%	2590
	21st to end	Night	13% 4 1 4 4 3 3 3 5% 6% 54%	2660
December	1st to 10th	Night	23% 6% 1 3 2 2 2 2 4 7% 48%	2660
	11th to 20th	Night	33% 5% 1 3 3 3 3 3 5% 7% 34%	3276
	21st to end	Night	27% 7% 2 5% 3 3 3 2 5% 6% 37%	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	45% 5% 15% 25% 8% 2	2539
	11th to 20th	Day	57% 2 9% 15% 10% 7%	2800
	21st to end	Day	52% 3 14% 13% 13% 5%	3146
February	1st to 10th	Day	39% 4 10% 20% 18% 8%	1710
	11th to 20th	Day	36% 3 10% 21% 24% 6%	1678
	21st to end	Day	37% 5% 9% 23% 20% 6%	1570
March	1st to 10th	Day	55% 6% 7% 12% 16% 3	3370
	11th to 20th	Day	30% 3 9% 24% 28% 6%	3490
	21st to end	Day	47% 5% 12% 22% 11% 3	3877
April	1st to 10th	Day	37% 4 13% 22% 19% 5%	2280
	11th to 20th	Day	30% 3 12% 25% 20% 10%	2252
	21st to end	Day	21% 4 12% 27% 28% 8%	2304
May	1st to 10th	Day	18% 4 9% 24% 28% 18%	4110
	11th to 20th	Day	12% 2 5% 16% 32% 32%	4349
	21st to end	Day	13% 2 11% 30% 32% 11%	4814
June	1st to 10th	Day	21% 4 9% 23% 27% 15%	2660
	11th to 20th	Day	10% 2 7% 20% 33% 27%	2660
	21st to end	Day	11% 2 3 14% 31% 39%	2660
July	1st to 10th	Day	4 1 2 8% 16% 70%	4351
	11th to 20th	Day	9% 1 3 7% 22% 58%	4325
	21st to end	Day	4 1 1 11% 31% 52%	4315
August	1st to 10th	Day	10% 1 2 10% 25% 51%	4076
	11th to 20th	Day	5% 1 2 18% 38% 36%	4013
	21st to end	Day	7% 2 4 16% 37% 33%	4179
September	1st to 10th	Day	4 1 2 10% 25% 58%	2280
	11th to 20th	Day	13% 2 5% 21% 36% 23%	2280
	21st to end	Day	11% 2 5% 18% 32% 31%	2000
October	1st to 10th	Day	10% 2 4 15% 22% 46%	3180
	11th to 20th	Day	16% 2 8% 26% 31% 17%	3161
	21st to end	Day	28% 3 8% 22% 25% 13%	3448
November	1st to 10th	Day	32% 4 9% 25% 18% 12%	1842
	11th to 20th	Day	33% 5% 14% 23% 17% 8%	1610
	21st to end	Day	30% 3 10% 22% 24% 11%	1520
December	1st to 10th	Day	38% 2 8% 20% 22% 10%	1520
	11th to 20th	Day	56% 3 7% 16% 14% 4	1928
	21st to end	Day	49% 4 11% 21% 13% 3	2794
January	1st to 10th	Night	44% 4 20% 20% 8% 3	4406
	11th to 20th	Night	53% 5% 9% 13% 13% 7%	4163
	21st to end	Night	57% 3 10% 12% 13% 5%	4521
February	1st to 10th	Night	38% 3 9% 22% 20% 9%	2470
	11th to 20th	Night	38% 3 9% 21% 23% 7%	2399
	21st to end	Night	36% 3 11% 22% 22% 6%	1884
March	1st to 10th	Night	48% 6% 13% 16% 14% 3	3502
	11th to 20th	Night	30% 3 8% 29% 23% 8%	3490
	21st to end	Night	39% 7% 14% 26% 11% 2	3774
April	1st to 10th	Night	37% 4 15% 21% 17% 7%	1900
	11th to 20th	Night	28% 4 13% 27% 19% 9%	1879
	21st to end	Night	20% 4 13% 32% 25% 6%	1872
May	1st to 10th	Night	19% 3 10% 21% 33% 15%	2860
	11th to 20th	Night	12% 3 7% 17% 37% 24%	2548
	21st to end	Night	14% 3 11% 37% 27% 8%	2762
June	1st to 10th	Night	23% 5% 10% 24% 28% 9%	1520
	11th to 20th	Night	10% 2 8% 21% 36% 23%	1520
	21st to end	Night	10% 1 4 16% 36% 33%	1520
July	1st to 10th	Night	4 1 1 9% 19% 67%	2500
	11th to 20th	Night	9% 1 3 6% 20% 61%	2510
	21st to end	Night	3 1 2 10% 32% 51%	3011
August	1st to 10th	Night	12% 1 2 11% 28% 46%	2839
	11th to 20th	Night	4 1 2 16% 41% 35%	2892
	21st to end	Night	9% 1 2 17% 38% 34%	3498
September	1st to 10th	Night	4 2 2 10% 26% 56%	1900
	11th to 20th	Night	11% 3 5% 22% 38% 22%	1900
	21st to end	Night	11% 3 5% 19% 27% 35%	2176
October	1st to 10th	Night	12% 2 4 11% 22% 50%	3800
	11th to 20th	Night	15% 3 7% 31% 28% 16%	3777
	21st to end	Night	20% 2 8% 26% 28% 16%	4121
November	1st to 10th	Night	29% 4 13% 24% 18% 12%	2454
	11th to 20th	Night	32% 5% 14% 23% 18% 9%	2590
	21st to end	Night	30% 3 10% 22% 22% 12%	2660
December	1st to 10th	Night	38% 2 9% 18% 22% 10%	2660
	11th to 20th	Night	52% 3 7% 16% 19% 3	3276
	21st to end	Night	49% 3 11% 19% 13% 3	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	41% 8% 22% 20% 8% 2	180
	11th to 20th	Day	30% 7% 24% 24% 11% 4	336
	21st to end	Day	24% 10% 21% 28% 14% 4	407
February	1st to 10th	Day	23% 12% 22% 26% 16% 2	370
	11th to 20th	Day	24% 13% 30% 23% 8% 2	367
	21st to end	Day	21% 11% 30% 27% 9% 2	382
March	1st to 10th	Day	31% 18% 26% 18% 6% 1	460
	11th to 20th	Day	27% 12% 24% 22% 12% 3	460
	21st to end	Day	26% 15% 25% 23% 10% 1	506
April	1st to 10th	Day	23% 16% 24% 26% 10% 1	460
	11th to 20th	Day	21% 16% 26% 23% 12% 3	452
	21st to end	Day	9% 18% 29% 25% 14% 4	460
May	1st to 10th	Day	11% 20% 33% 22% 12% 3	463
	11th to 20th	Day	11% 13% 28% 29% 15% 5%	488
	21st to end	Day	9% 13% 26% 32% 16% 4	529
June	1st to 10th	Day	8% 13% 22% 32% 21% 4	490
	11th to 20th	Day	6% 18% 30% 30% 14% 3	490
	21st to end	Day	3 7% 27% 34% 24% 5%	490
July	1st to 10th	Day	1 5% 27% 41% 21% 6%	486
	11th to 20th	Day	4 19% 44% 25% 8%	484
	21st to end	Day	2 16% 45% 27% 9%	531
August	1st to 10th	Day	2 2 22% 38% 25% 10%	487
	11th to 20th	Day	1 5% 20% 36% 27% 10%	477
	21st to end	Day	2 5% 20% 39% 27% 7%	539
September	1st to 10th	Day	1 3 22% 40% 28% 6%	490
	11th to 20th	Day	5% 7% 22% 39% 20% 7%	490
	21st to end	Day	3 8% 27% 36% 22% 4	490
October	1st to 10th	Day	6% 11% 24% 31% 23% 6%	490
	11th to 20th	Day	8% 6% 26% 32% 22% 6%	490
	21st to end	Day	15% 9% 25% 28% 19% 4	539
November	1st to 10th	Day	17% 8% 24% 27% 20% 4	378
	11th to 20th	Day	18% 4 27% 27% 19% 6%	222
	21st to end	Day	14% 9% 28% 31% 16% 3	180
December	1st to 10th	Day	26% 10% 24% 18% 16% 5%	180
	11th to 20th	Day	28% 5% 25% 25% 12% 6%	180
	21st to end	Day	21% 10% 27% 26% 14% 3	198
January	1st to 10th	Night	26% 5% 22% 28% 16% 3	760
	11th to 20th	Night	24% 7% 23% 31% 12% 3	760
	21st to end	Night	23% 6% 23% 29% 17% 2	836
February	1st to 10th	Night	22% 6% 23% 33% 15% 2	760
	11th to 20th	Night	22% 8% 24% 30% 13% 2	744
	21st to end	Night	19% 8% 27% 35% 10% 1	628
March	1st to 10th	Night	28% 8% 24% 26% 13% 2	760
	11th to 20th	Night	23% 6% 22% 30% 18% 1	760
	21st to end	Night	21% 11% 25% 31% 12% 1	836
April	1st to 10th	Night	17% 11% 28% 28% 14% 1	760
	11th to 20th	Night	14% 9% 29% 32% 14% 2	751
	21st to end	Night	9% 10% 30% 32% 18% 1	732
May	1st to 10th	Night	10% 12% 30% 31% 16% 1	570
	11th to 20th	Night	9% 7% 25% 36% 23% 1	393
	21st to end	Night	9% 9% 28% 34% 21%	411
June	1st to 10th	Night	7% 8% 27% 38% 20% 1	380
	11th to 20th	Night	6% 9% 31% 37% 16% 1	380
	21st to end	Night	4 3 21% 49% 23% 1	380
July	1st to 10th	Night	1 1 16% 46% 34% 2	370
	11th to 20th	Night	1 1 16% 42% 37% 3	373
	21st to end	Night	1 8% 42% 45% 4	624
August	1st to 10th	Night	3 2 9% 39% 42% 5%	567
	11th to 20th	Night	2 1 14% 40% 39% 4	591
	21st to end	Night	2 2 10% 40% 43% 3	836
September	1st to 10th	Night	1 2 17% 43% 36% 2	760
	11th to 20th	Night	4 4 13% 38% 38% 4	760
	21st to end	Night	4 6% 20% 36% 31% 4	760
October	1st to 10th	Night	6% 7% 20% 37% 26% 3	760
	11th to 20th	Night	7% 4 23% 35% 27% 4	760
	21st to end	Night	13% 5% 23% 34% 21% 4	836
November	1st to 10th	Night	13% 6% 19% 35% 24% 3	780
	11th to 20th	Night	16% 4 23% 37% 18% 1	764
	21st to end	Night	15% 6% 24% 35% 18% 2	760
December	1st to 10th	Night	26% 4 21% 33% 13% 3	760
	11th to 20th	Night	28% 5% 22% 30% 14% 2	760
	21st to end	Night	25% 6% 26% 31% 12% 1	836

Page generated at 2024-11-08 19:45:37. Version ac07

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