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 2026-01-02.

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	10% 3 1 3 2 2 2 2 4 5% 65%	136183
	Night	12% 4 1 3 2 2 3 2 4 5% 61%	132574
Transparency	Day	23% 3 7% 20% 25% 22%	131051
	Night	27% 3 8% 20% 24% 18%	128696
Seeing	Day	13% 10% 25% 30% 18% 5%	16521
	Night	14% 6% 22% 34% 21% 2	25740

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	20% 6% 2 5% 4 4 4 3 5% 7% 39%	3647
	11th to 20th	Day	20% 8% 2 4 2 2 2 1 2 3 55%	4026
	21st to end	Day	23% 5% 1 3 2 2 2 2 3 5% 51%	4510
February	1st to 10th	Day	20% 6% 1 4 4 4 4 3 5% 6% 44%	1800
	11th to 20th	Day	17% 7% 1 4 4 3 3 3 4 7% 48%	1760
	21st to end	Day	16% 5% 2 5% 3 3 4 3 5% 7% 46%	1650
March	1st to 10th	Day	21% 10% 2 7% 4 3 4 2 3 5% 39%	4841
	11th to 20th	Day	19% 7% 1 5% 3 3 3 2 4 6% 47%	5000
	21st to end	Day	21% 7% 2 6% 4 4 4 3 6% 8% 37%	5564
April	1st to 10th	Day	16% 6% 2 5% 3 4 3 3 6% 7% 45%	2400
	11th to 20th	Day	12% 4 2 4 3 2 3 3 5% 6% 55%	2369
	21st to end	Day	5% 4 1 5% 3 3 3 3 4 7% 61%	2425
May	1st to 10th	Day	5% 3 1 3 2 2 2 2 4 6% 70%	5880
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 6% 74%	6233
	21st to end	Day	3 1 1 2 1 1 2 2 4 6% 77%	6902
June	1st to 10th	Day	6% 3 1 3 3 3 4 3 6% 7% 62%	2800
	11th to 20th	Day	2 2 1 2 2 2 2 4 6% 77%	2800
	21st to end	Day	4 2 1 1 1 1 2 2 3 3 80%	2800
July	1st to 10th	Day	1 1 1 1 1 1 2 2 90%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 89%	6287
	21st to end	Day	1 1 1 1 2 2 4 5% 82%	6402
August	1st to 10th	Day	2 1 1 1 1 1 2 4 4 82%	5777
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 88%	5718
	21st to end	Day	1 1 1 1 1 1 1 1 2 4 84%	5984
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2400
	11th to 20th	Day	4 2 2 1 2 2 2 4 5% 73%	2400
	21st to end	Day	3 2 1 2 1 2 2 1 3 5% 78%	2105
October	1st to 10th	Day	4 1 1 2 1 1 2 2 3 4 79%	3280
	11th to 20th	Day	5% 2 1 2 1 2 2 4 5% 8% 68%	3261
	21st to end	Day	10% 3 2 5% 4 3 4 3 5% 7% 55%	3558
November	1st to 10th	Day	13% 4 2 4 3 4 3 3 4 7% 52%	1936
	11th to 20th	Day	16% 6% 1 5% 2 3 4 3 6% 8% 47%	1769
	21st to end	Day	13% 4 1 3 3 3 3 2 5% 7% 56%	1680
December	1st to 10th	Day	12% 4 1 3 3 4 4 2 4 6% 57%	2700
	11th to 20th	Day	32% 6% 2 4 4 4 5% 3 5% 7% 28%	3108
	21st to end	Day	32% 6% 2 4 3 3 4 3 5% 5% 33%	4092
January	1st to 10th	Night	20% 6% 2 5% 4 4 4 4 6% 7% 39%	6320
	11th to 20th	Night	19% 7% 1 4 2 2 2 2 3 4 53%	5946
	21st to end	Night	20% 6% 2 5% 3 3 3 2 4 4 48%	6468
February	1st to 10th	Night	21% 5% 1 4 3 3 3 3 5% 6% 46%	2600
	11th to 20th	Night	18% 6% 1 4 3 3 4 4 4 6% 47%	2526
	21st to end	Night	14% 5% 2 5% 5% 3 4 3 5% 6% 49%	1980
March	1st to 10th	Night	18% 7% 2 5% 3 4 4 3 5% 6% 43%	5038
	11th to 20th	Night	19% 5% 2 4 3 3 3 2 4 7% 49%	5000
	21st to end	Night	16% 7% 3 7% 4 4 4 3 4 7% 40%	5409
April	1st to 10th	Night	14% 6% 3 5% 4 4 4 3 5% 7% 47%	2000
	11th to 20th	Night	9% 4 2 4 3 3 3 4 5% 6% 57%	1979
	21st to end	Night	7% 4 2 3 3 2 2 3 5% 7% 62%	1970
May	1st to 10th	Night	5% 3 1 3 2 2 2 1 3 6% 73%	4100
	11th to 20th	Night	4 2 1 2 2 2 2 3 4 6% 72%	3662
	21st to end	Night	3 2 1 2 1 1 2 2 4 5% 78%	3972
June	1st to 10th	Night	6% 4 1 4 3 2 3 4 6% 6% 61%	1600
	11th to 20th	Night	4 2 1 2 1 1 2 1 4 5% 79%	1600
	21st to end	Night	3 2 1 1 1 2 1 3 3 82%	1600
July	1st to 10th	Night	1 1 1 1 1 1 2 2 90%	3640
	11th to 20th	Night	1 1 1 1 1 1 2 1 2 2 88%	3658
	21st to end	Night	1 1 1 2 2 3 5% 85%	4472
August	1st to 10th	Night	2 1 1 1 1 1 2 2 3 3 83%	4035
	11th to 20th	Night	1 1 1 1 1 1 1 2 2 87%	4133
	21st to end	Night	4 1 2 1 1 1 1 2 3 84%	5015
September	1st to 10th	Night	1 1 1 1 1 1 1 2 4 87%	2000
	11th to 20th	Night	3 1 1 1 2 2 2 2 3 6% 76%	2000
	21st to end	Night	3 2 1 2 2 1 2 2 3 5% 77%	2290
October	1st to 10th	Night	3 2 1 2 2 2 3 2 3 3 80%	3920
	11th to 20th	Night	5% 2 1 2 2 2 2 2 3 6% 73%	3897
	21st to end	Night	8% 2 1 2 2 2 3 3 6% 8% 63%	4253
November	1st to 10th	Night	13% 4 1 4 3 2 4 3 6% 8% 52%	2580
	11th to 20th	Night	15% 4 2 4 3 4 4 4 6% 8% 47%	2849
	21st to end	Night	13% 4 1 4 3 3 3 3 5% 6% 55%	2940
December	1st to 10th	Night	13% 4 1 2 2 2 2 3 4 6% 61%	4700
	11th to 20th	Night	30% 7% 2 4 3 3 5% 4 6% 7% 30%	5316
	21st to end	Night	35% 6% 2 4 3 3 3 2 4 5% 35%	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	43% 6% 13% 21% 13% 3	3647
	11th to 20th	Day	39% 1 6% 22% 21% 10%	4026
	21st to end	Day	39% 2 10% 12% 20% 17%	4510
February	1st to 10th	Day	40% 4 9% 19% 18% 9%	1800
	11th to 20th	Day	37% 3 10% 21% 24% 5%	1769
	21st to end	Day	36% 4 9% 23% 21% 7%	1650
March	1st to 10th	Day	47% 5% 8% 17% 20% 3	4841
	11th to 20th	Day	40% 4 12% 19% 21% 5%	5000
	21st to end	Day	44% 6% 12% 26% 10% 2	5564
April	1st to 10th	Day	36% 4 14% 22% 20% 5%	2400
	11th to 20th	Day	29% 3 11% 25% 20% 11%	2372
	21st to end	Day	22% 4 12% 27% 28% 8%	2425
May	1st to 10th	Day	16% 3 8% 25% 29% 20%	5880
	11th to 20th	Day	13% 2 5% 23% 33% 25%	6236
	21st to end	Day	10% 2 8% 31% 39% 10%	6904
June	1st to 10th	Day	20% 4 9% 24% 28% 15%	2800
	11th to 20th	Day	10% 2 7% 20% 33% 27%	2800
	21st to end	Day	10% 2 3 15% 32% 39%	2800
July	1st to 10th	Day	4 1 2 12% 21% 60%	6251
	11th to 20th	Day	6% 1 2 6% 22% 63%	6212
	21st to end	Day	6% 2 5% 22% 29% 36%	6217
August	1st to 10th	Day	10% 1 2 11% 26% 50%	4206
	11th to 20th	Day	5% 1 2 18% 38% 36%	4141
	21st to end	Day	7% 2 4 16% 38% 33%	4311
September	1st to 10th	Day	5% 1 2 12% 24% 56%	2400
	11th to 20th	Day	14% 2 5% 21% 35% 23%	2400
	21st to end	Day	12% 2 5% 18% 32% 31%	2105
October	1st to 10th	Day	11% 2 4 15% 22% 45%	3280
	11th to 20th	Day	16% 2 8% 26% 30% 17%	3261
	21st to end	Day	28% 3 8% 22% 26% 13%	3558
November	1st to 10th	Day	31% 4 9% 26% 18% 11%	1936
	11th to 20th	Day	35% 5% 14% 23% 17% 8%	1769
	21st to end	Day	29% 3 10% 22% 24% 12%	1680
December	1st to 10th	Day	29% 2 6% 19% 32% 12%	2700
	11th to 20th	Day	56% 5% 11% 15% 10% 3	3108
	21st to end	Day	54% 4 9% 18% 13% 2	4092
January	1st to 10th	Night	43% 5% 16% 18% 15% 3	6320
	11th to 20th	Night	37% 3 7% 19% 24% 10%	5946
	21st to end	Night	42% 2 8% 10% 16% 22%	6468
February	1st to 10th	Night	39% 3 8% 21% 20% 9%	2600
	11th to 20th	Night	38% 3 10% 20% 22% 6%	2528
	21st to end	Night	35% 3 11% 21% 23% 7%	1980
March	1st to 10th	Night	42% 5% 12% 20% 16% 5%	5038
	11th to 20th	Night	36% 4 10% 25% 19% 6%	5000
	21st to end	Night	41% 7% 13% 27% 11% 2	5409
April	1st to 10th	Night	36% 4 15% 21% 17% 7%	2000
	11th to 20th	Night	27% 4 13% 26% 19% 11%	1979
	21st to end	Night	21% 4 13% 32% 25% 6%	1970
May	1st to 10th	Night	16% 2 8% 22% 36% 17%	4097
	11th to 20th	Night	13% 3 7% 25% 33% 19%	3662
	21st to end	Night	11% 2 9% 36% 35% 6%	3972
June	1st to 10th	Night	22% 5% 10% 24% 29% 10%	1600
	11th to 20th	Night	10% 2 7% 22% 37% 23%	1600
	21st to end	Night	10% 1 4 16% 37% 32%	1600
July	1st to 10th	Night	4 1 2 11% 28% 54%	3600
	11th to 20th	Night	6% 1 2 5% 23% 64%	3610
	21st to end	Night	4 2 7% 20% 31% 36%	4345
August	1st to 10th	Night	11% 1 2 12% 29% 45%	2929
	11th to 20th	Night	4 1 2 16% 41% 35%	2984
	21st to end	Night	9% 1 2 16% 39% 34%	3608
September	1st to 10th	Night	6% 2 2 12% 25% 54%	2000
	11th to 20th	Night	11% 3 5% 22% 38% 21%	2000
	21st to end	Night	11% 3 6% 19% 27% 35%	2290
October	1st to 10th	Night	13% 2 4 11% 22% 48%	3920
	11th to 20th	Night	15% 3 7% 31% 28% 15%	3897
	21st to end	Night	20% 2 8% 26% 28% 16%	4253
November	1st to 10th	Night	30% 4 12% 25% 17% 11%	2580
	11th to 20th	Night	34% 5% 13% 23% 17% 8%	2849
	21st to end	Night	30% 3 10% 22% 22% 12%	2940
December	1st to 10th	Night	26% 2 7% 19% 33% 14%	4700
	11th to 20th	Night	55% 4 8% 18% 13% 3	5316
	21st to end	Night	55% 3 10% 17% 13% 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	39% 10% 23% 19% 7% 1	202
	11th to 20th	Day	28% 7% 25% 24% 11% 5%	365
	21st to end	Day	23% 10% 20% 28% 14% 4	440
February	1st to 10th	Day	25% 12% 23% 24% 15% 2	400
	11th to 20th	Day	24% 14% 30% 22% 7% 2	398
	21st to end	Day	20% 11% 30% 29% 9% 1	414
March	1st to 10th	Day	30% 17% 26% 19% 7% 1	500
	11th to 20th	Day	28% 12% 24% 22% 11% 2	500
	21st to end	Day	26% 15% 25% 23% 11% 1	550
April	1st to 10th	Day	22% 16% 24% 26% 10% 1	500
	11th to 20th	Day	19% 15% 28% 23% 12% 3	492
	21st to end	Day	10% 17% 29% 26% 14% 4	500
May	1st to 10th	Day	10% 19% 33% 23% 12% 3	503
	11th to 20th	Day	11% 13% 29% 28% 14% 5%	528
	21st to end	Day	8% 13% 26% 32% 17% 4	573
June	1st to 10th	Day	7% 12% 23% 33% 20% 4	530
	11th to 20th	Day	6% 18% 30% 29% 15% 3	530
	21st to end	Day	3 7% 26% 34% 24% 5%	530
July	1st to 10th	Day	2 5% 28% 40% 21% 6%	526
	11th to 20th	Day	3 19% 45% 25% 8%	524
	21st to end	Day	2 17% 44% 27% 10%	575
August	1st to 10th	Day	2 2 22% 39% 25% 10%	527
	11th to 20th	Day	1 5% 20% 36% 27% 11%	517
	21st to end	Day	2 4 19% 39% 27% 8%	583
September	1st to 10th	Day	2 4 22% 40% 27% 6%	530
	11th to 20th	Day	5% 6% 22% 39% 21% 7%	530
	21st to end	Day	5% 7% 27% 36% 22% 4	530
October	1st to 10th	Day	7% 10% 25% 30% 23% 5%	530
	11th to 20th	Day	8% 6% 28% 31% 22% 5%	530
	21st to end	Day	15% 9% 24% 28% 20% 4	583
November	1st to 10th	Day	17% 8% 23% 28% 21% 4	412
	11th to 20th	Day	20% 7% 25% 26% 16% 5%	267
	21st to end	Day	15% 7% 26% 31% 17% 3	220
December	1st to 10th	Day	21% 10% 22% 23% 18% 6%	220
	11th to 20th	Day	28% 5% 24% 25% 12% 6%	220
	21st to end	Day	26% 11% 24% 23% 14% 2	242
January	1st to 10th	Night	26% 6% 22% 27% 15% 3	804
	11th to 20th	Night	23% 8% 23% 31% 13% 3	800
	21st to end	Night	23% 6% 23% 29% 17% 2	880
February	1st to 10th	Night	23% 6% 24% 32% 14% 2	800
	11th to 20th	Night	22% 9% 26% 29% 12% 2	784
	21st to end	Night	18% 8% 29% 34% 9% 1	660
March	1st to 10th	Night	27% 8% 24% 27% 13% 2	800
	11th to 20th	Night	23% 7% 22% 30% 17% 1	800
	21st to end	Night	21% 10% 26% 31% 11% 1	880
April	1st to 10th	Night	17% 11% 28% 29% 14% 1	800
	11th to 20th	Night	13% 9% 30% 32% 14% 2	791
	21st to end	Night	9% 9% 30% 32% 18% 1	770
May	1st to 10th	Night	9% 12% 29% 32% 16% 1	600
	11th to 20th	Night	9% 7% 26% 35% 22% 1	414
	21st to end	Night	8% 9% 27% 35% 20%	433
June	1st to 10th	Night	7% 8% 27% 38% 20% 1	400
	11th to 20th	Night	5% 10% 30% 39% 16% 1	400
	21st to end	Night	4 3 21% 49% 23% 1	400
July	1st to 10th	Night	1 1 18% 46% 33% 2	390
	11th to 20th	Night	1 1 15% 43% 37% 3	393
	21st to end	Night	1 7% 41% 46% 4	657
August	1st to 10th	Night	3 2 10% 39% 42% 5%	597
	11th to 20th	Night	1 1 14% 40% 39% 4	623
	21st to end	Night	2 2 10% 41% 43% 3	880
September	1st to 10th	Night	1 2 16% 43% 35% 2	800
	11th to 20th	Night	4 4 14% 38% 38% 4	800
	21st to end	Night	4 6% 20% 36% 31% 4	800
October	1st to 10th	Night	7% 7% 21% 37% 26% 3	800
	11th to 20th	Night	8% 4 23% 35% 26% 4	800
	21st to end	Night	13% 5% 23% 34% 21% 4	880
November	1st to 10th	Night	14% 6% 19% 35% 23% 3	820
	11th to 20th	Night	18% 5% 23% 36% 17% 1	840
	21st to end	Night	15% 6% 24% 36% 17% 2	840
December	1st to 10th	Night	23% 4 22% 33% 14% 3	840
	11th to 20th	Night	28% 4 22% 30% 14% 2	840
	21st to end	Night	28% 6% 25% 29% 11% 1	924

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