Tulelake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tulelake clear sky chart from 2005-11-06 to 2026-10-14.

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	6% 6% 2 5% 3 3 3 3 5% 6% 57%	158583
	Night	8% 7% 2 5% 4 4 4 3 4 6% 54%	150592
Transparency	Day	27% 5% 8% 21% 23% 16%	153452
	Night	31% 6% 10% 23% 20% 11%	146715
Seeing	Day	11% 10% 20% 25% 22% 12%	17372
	Night	10% 6% 19% 38% 24% 3	26439

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	14% 16% 5% 10% 6% 5% 4 4 5% 6% 25%	4722
	11th to 20th	Day	11% 11% 3 5% 2 2 3 2 4 6% 51%	4818
	21st to end	Day	11% 8% 2 7% 4 4 4 4 5% 7% 45%	5843
February	1st to 10th	Day	9% 10% 3 7% 5% 6% 4 4 6% 9% 37%	1890
	11th to 20th	Day	9% 11% 4 8% 6% 6% 5% 4 5% 8% 35%	1887
	21st to end	Day	8% 12% 3 8% 6% 6% 6% 4 4 8% 34%	1730
March	1st to 10th	Day	10% 18% 5% 8% 4 4 3 3 5% 7% 33%	4746
	11th to 20th	Day	7% 13% 3 5% 5% 4 4 3 5% 6% 44%	5110
	21st to end	Day	10% 14% 4 9% 6% 5% 5% 4 5% 6% 32%	5820
April	1st to 10th	Day	9% 9% 3 9% 6% 6% 6% 4 5% 6% 37%	2520
	11th to 20th	Day	11% 9% 3 6% 4 3 4 3 6% 7% 44%	2489
	21st to end	Day	7% 6% 2 7% 4 4 3 3 5% 8% 50%	2520
May	1st to 10th	Day	5% 5% 1 4 3 3 3 3 5% 7% 61%	7939
	11th to 20th	Day	3 3 1 3 3 3 3 3 5% 6% 67%	8160
	21st to end	Day	6% 4 1 4 3 3 3 3 5% 6% 62%	8992
June	1st to 10th	Day	7% 5% 2 5% 4 4 4 4 6% 7% 52%	2940
	11th to 20th	Day	3 3 1 3 3 3 3 3 4 6% 67%	2940
	21st to end	Day	4 2 1 2 2 2 3 2 4 5% 74%	2940
July	1st to 10th	Day	1 1 2 2 2 2 2 3 4 80%	8219
	11th to 20th	Day	3 2 1 3 2 2 3 2 4 4 73%	8220
	21st to end	Day	2 2 1 2 2 2 3 3 4 5% 75%	8760
August	1st to 10th	Day	1 1 2 2 2 2 3 4 5% 76%	7547
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 5% 78%	7396
	21st to end	Day	3 2 1 3 2 2 3 2 4 7% 73%	7750
September	1st to 10th	Day	2 1 1 2 2 2 2 2 4 5% 78%	2520
	11th to 20th	Day	4 3 1 3 3 3 3 3 4 6% 67%	2520
	21st to end	Day	4 3 1 4 3 2 3 2 4 7% 68%	2247
October	1st to 10th	Day	4 3 1 3 2 2 3 2 3 5% 73%	3380
	11th to 20th	Day	6% 3 1 3 3 3 3 4 6% 10% 58%	3292
	21st to end	Day	9% 6% 1 6% 5% 5% 5% 4 6% 8% 45%	3507
November	1st to 10th	Day	13% 9% 3 6% 4 5% 4 3 4 8% 40%	1854
	11th to 20th	Day	13% 8% 3 7% 6% 4 5% 5% 8% 8% 33%	1785
	21st to end	Day	9% 9% 2 9% 5% 4 5% 4 5% 9% 40%	1680
December	1st to 10th	Day	6% 7% 2 7% 4 4 4 4 6% 9% 47%	2700
	11th to 20th	Day	19% 12% 4 8% 6% 5% 5% 4 6% 9% 22%	3108
	21st to end	Day	15% 12% 4 11% 7% 7% 6% 5% 7% 7% 19%	4092
January	1st to 10th	Night	16% 14% 4 8% 6% 5% 5% 4 5% 7% 24%	8172
	11th to 20th	Night	9% 9% 2 4 3 3 3 2 4 6% 54%	8132
	21st to end	Night	12% 8% 3 6% 5% 5% 5% 4 5% 7% 40%	8371
February	1st to 10th	Night	9% 10% 3 6% 5% 6% 5% 4 5% 7% 40%	2730
	11th to 20th	Night	10% 11% 3 7% 4 5% 4 4 5% 7% 40%	2620
	21st to end	Night	8% 9% 3 7% 5% 5% 5% 4 5% 8% 39%	2076
March	1st to 10th	Night	8% 15% 4 8% 5% 4 4 4 5% 7% 36%	5366
	11th to 20th	Night	9% 10% 2 5% 4 4 3 4 6% 8% 46%	5110
	21st to end	Night	10% 12% 4 8% 6% 5% 5% 4 5% 8% 34%	5397
April	1st to 10th	Night	10% 9% 3 6% 5% 5% 5% 4 6% 8% 41%	2100
	11th to 20th	Night	8% 9% 2 6% 4 4 3 3 4 6% 49%	2079
	21st to end	Night	9% 6% 2 6% 3 3 3 3 5% 8% 52%	2100
May	1st to 10th	Night	6% 4 2 4 3 3 3 3 3 4 65%	4974
	11th to 20th	Night	3 3 1 3 2 3 3 3 5% 6% 68%	4700
	21st to end	Night	6% 4 1 3 2 2 3 2 4 6% 67%	5181
June	1st to 10th	Night	8% 6% 2 5% 3 4 4 3 5% 7% 54%	1680
	11th to 20th	Night	4 3 1 4 2 3 3 2 4 5% 69%	1680
	21st to end	Night	3 3 1 2 3 2 3 2 4 4 76%	1680
July	1st to 10th	Night	2 1 2 2 2 2 2 2 4 81%	4740
	11th to 20th	Night	3 3 1 3 2 2 2 2 3 3 76%	4740
	21st to end	Night	2 1 1 3 2 2 3 3 4 5% 74%	5320
August	1st to 10th	Night	1 1 1 2 2 2 2 2 3 5% 80%	5275
	11th to 20th	Night	1 1 2 2 2 2 2 3 4 80%	5467
	21st to end	Night	3 2 1 3 2 2 3 2 3 6% 72%	6499
September	1st to 10th	Night	2 1 1 2 1 1 2 2 3 4 80%	2100
	11th to 20th	Night	5% 3 1 3 2 2 3 2 5% 5% 69%	2100
	21st to end	Night	4 3 1 4 2 2 2 2 3 6% 70%	2370
October	1st to 10th	Night	3 3 1 3 2 2 3 2 3 3 77%	4040
	11th to 20th	Night	6% 4 1 4 3 3 3 2 4 7% 63%	3933
	21st to end	Night	6% 5% 2 4 3 4 4 4 7% 9% 53%	4300
November	1st to 10th	Night	12% 8% 2 5% 5% 4 4 4 5% 9% 42%	2665
	11th to 20th	Night	14% 7% 2 6% 5% 5% 5% 4 6% 10% 36%	2833
	21st to end	Night	9% 9% 2 5% 4 5% 4 4 6% 8% 44%	2940
December	1st to 10th	Night	8% 5% 1 4 3 4 4 3 6% 9% 51%	4700
	11th to 20th	Night	18% 11% 4 8% 6% 5% 6% 4 6% 8% 24%	5316
	21st to end	Night	18% 12% 4 10% 6% 6% 5% 3 5% 6% 24%	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	55% 10% 12% 18% 4	4723
	11th to 20th	Day	35% 4 7% 23% 21% 10%	4818
	21st to end	Day	37% 6% 10% 19% 21% 8%	5843
February	1st to 10th	Day	41% 7% 16% 21% 13% 1	1890
	11th to 20th	Day	45% 7% 14% 21% 11% 2	1896
	21st to end	Day	46% 7% 15% 18% 11% 3	1730
March	1st to 10th	Day	48% 8% 8% 24% 9% 3	4746
	11th to 20th	Day	39% 7% 14% 23% 18% 1	5110
	21st to end	Day	48% 8% 13% 21% 8% 1	5820
April	1st to 10th	Day	46% 6% 13% 19% 13% 2	2520
	11th to 20th	Day	38% 5% 13% 23% 17% 4	2492
	21st to end	Day	31% 6% 15% 26% 19% 3	2520
May	1st to 10th	Day	23% 4 6% 27% 31% 9%	7939
	11th to 20th	Day	20% 3 8% 25% 35% 9%	8163
	21st to end	Day	23% 4 9% 33% 27% 4	8994
June	1st to 10th	Day	29% 7% 12% 26% 22% 5%	2940
	11th to 20th	Day	19% 4 8% 26% 32% 11%	2940
	21st to end	Day	14% 3 6% 24% 32% 22%	2940
July	1st to 10th	Day	10% 2 3 15% 27% 43%	8151
	11th to 20th	Day	17% 2 2 10% 23% 47%	8145
	21st to end	Day	13% 2 4 16% 29% 36%	8563
August	1st to 10th	Day	10% 2 3 9% 23% 52%	5976
	11th to 20th	Day	9% 3 3 24% 41% 20%	5831
	21st to end	Day	12% 2 3 23% 38% 22%	6077
September	1st to 10th	Day	11% 3 4 15% 30% 38%	2520
	11th to 20th	Day	19% 4 7% 20% 31% 20%	2520
	21st to end	Day	18% 4 8% 23% 28% 20%	2247
October	1st to 10th	Day	17% 3 7% 16% 31% 27%	3380
	11th to 20th	Day	21% 4 10% 35% 22% 7%	3292
	21st to end	Day	36% 6% 10% 24% 18% 6%	3507
November	1st to 10th	Day	41% 7% 13% 23% 14% 4	1854
	11th to 20th	Day	45% 8% 16% 16% 14% 1	1785
	21st to end	Day	40% 6% 13% 20% 17% 3	1680
December	1st to 10th	Day	33% 7% 11% 26% 20% 3	2700
	11th to 20th	Day	57% 8% 15% 15% 5%	3108
	21st to end	Day	57% 12% 12% 15% 4	4092
January	1st to 10th	Night	54% 10% 15% 16% 4	8172
	11th to 20th	Night	31% 6% 8% 22% 28% 6%	8132
	21st to end	Night	42% 6% 9% 17% 19% 7%	8371
February	1st to 10th	Night	42% 7% 13% 22% 13% 2	2730
	11th to 20th	Night	42% 7% 14% 21% 13% 2	2622
	21st to end	Night	40% 8% 17% 20% 13% 3	2076
March	1st to 10th	Night	44% 8% 9% 25% 11% 2	5366
	11th to 20th	Night	33% 8% 13% 29% 17% 1	5110
	21st to end	Night	47% 9% 16% 20% 8% 1	5397
April	1st to 10th	Night	40% 7% 17% 23% 11% 2	2100
	11th to 20th	Night	36% 6% 15% 22% 16% 4	2079
	21st to end	Night	31% 6% 19% 27% 14% 2	2100
May	1st to 10th	Night	23% 4 9% 28% 32% 4	4972
	11th to 20th	Night	18% 4 13% 29% 30% 5%	4700
	21st to end	Night	20% 5% 12% 41% 20% 1	5182
June	1st to 10th	Night	30% 6% 15% 31% 16% 3	1680
	11th to 20th	Night	19% 6% 9% 30% 29% 7%	1680
	21st to end	Night	13% 3 8% 29% 33% 14%	1680
July	1st to 10th	Night	10% 2 3 18% 31% 35%	4700
	11th to 20th	Night	16% 2 2 9% 25% 46%	4692
	21st to end	Night	14% 2 5% 19% 27% 32%	5205
August	1st to 10th	Night	10% 2 3 11% 28% 47%	4169
	11th to 20th	Night	9% 4 4 31% 37% 17%	4305
	21st to end	Night	13% 2 4 27% 33% 20%	5092
September	1st to 10th	Night	10% 3 4 17% 29% 38%	2100
	11th to 20th	Night	17% 4 7% 22% 31% 19%	2100
	21st to end	Night	17% 3 7% 24% 24% 23%	2370
October	1st to 10th	Night	15% 3 6% 16% 32% 28%	4040
	11th to 20th	Night	22% 4 12% 35% 21% 7%	3933
	21st to end	Night	27% 5% 14% 29% 19% 7%	4300
November	1st to 10th	Night	38% 8% 13% 20% 16% 4	2665
	11th to 20th	Night	42% 9% 15% 18% 15% 1	2833
	21st to end	Night	36% 8% 16% 19% 17% 4	2940
December	1st to 10th	Night	28% 6% 14% 29% 21% 2	4700
	11th to 20th	Night	56% 8% 11% 18% 6% 1	5316
	21st to end	Night	55% 11% 11% 17% 5% 1	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	26% 15% 23% 24% 8% 3	220
	11th to 20th	Day	19% 10% 19% 22% 14% 15%	246
	21st to end	Day	16% 11% 16% 25% 23% 9%	473
February	1st to 10th	Day	15% 14% 21% 23% 19% 7%	430
	11th to 20th	Day	16% 17% 25% 23% 15% 4	447
	21st to end	Day	17% 14% 23% 30% 11% 4	446
March	1st to 10th	Day	20% 18% 27% 21% 13% 2	540
	11th to 20th	Day	18% 15% 25% 23% 17% 3	540
	21st to end	Day	21% 18% 22% 26% 12% 2	594
April	1st to 10th	Day	15% 17% 24% 23% 14% 6%	540
	11th to 20th	Day	18% 14% 22% 22% 15% 8%	532
	21st to end	Day	8% 16% 25% 24% 20% 8%	540
May	1st to 10th	Day	11% 13% 26% 26% 19% 5%	543
	11th to 20th	Day	15% 13% 23% 23% 15% 12%	568
	21st to end	Day	11% 9% 18% 26% 21% 15%	617
June	1st to 10th	Day	7% 12% 19% 24% 22% 16%	570
	11th to 20th	Day	6% 15% 23% 21% 22% 13%	570
	21st to end	Day	2 7% 18% 27% 26% 20%	570
July	1st to 10th	Day	4 4 18% 30% 27% 18%	566
	11th to 20th	Day	2 3 19% 29% 29% 19%	564
	21st to end	Day	2 3 14% 28% 31% 23%	619
August	1st to 10th	Day	2 1 16% 26% 28% 26%	567
	11th to 20th	Day	2 4 14% 25% 32% 23%	557
	21st to end	Day	3 5% 17% 26% 30% 19%	627
September	1st to 10th	Day	3 5% 19% 24% 33% 16%	570
	11th to 20th	Day	6% 8% 17% 27% 25% 17%	570
	21st to end	Day	7% 6% 18% 25% 29% 14%	570
October	1st to 10th	Day	8% 10% 17% 24% 23% 18%	570
	11th to 20th	Day	10% 11% 16% 24% 26% 13%	543
	21st to end	Day	13% 10% 17% 26% 21% 13%	556
November	1st to 10th	Day	16% 10% 17% 30% 18% 8%	330
	11th to 20th	Day	15% 8% 21% 23% 27% 7%	275
	21st to end	Day	12% 6% 17% 29% 26% 10%	220
December	1st to 10th	Day	14% 10% 17% 29% 18% 12%	220
	11th to 20th	Day	25% 10% 16% 24% 17% 8%	220
	21st to end	Day	16% 16% 23% 23% 21% 2	242
January	1st to 10th	Night	18% 8% 23% 32% 16% 3	840
	11th to 20th	Night	14% 9% 21% 33% 20% 3	840
	21st to end	Night	14% 4 21% 37% 20% 3	924
February	1st to 10th	Night	12% 7% 24% 38% 17% 1	840
	11th to 20th	Night	15% 8% 24% 35% 17% 2	824
	21st to end	Night	12% 11% 24% 39% 13% 1	692
March	1st to 10th	Night	15% 12% 26% 32% 13% 2	840
	11th to 20th	Night	15% 9% 20% 37% 18% 1	840
	21st to end	Night	15% 11% 26% 34% 14%	924
April	1st to 10th	Night	12% 10% 23% 37% 18% 1	840
	11th to 20th	Night	11% 9% 27% 34% 17% 3	831
	21st to end	Night	11% 8% 23% 37% 20% 2	840
May	1st to 10th	Night	8% 5% 25% 40% 20% 1	515
	11th to 20th	Night	10% 5% 21% 39% 23% 2	414
	21st to end	Night	10% 4 20% 40% 25% 1	455
June	1st to 10th	Night	10% 4 17% 44% 25% 1	420
	11th to 20th	Night	5% 5% 23% 45% 20% 1	420
	21st to end	Night	4 1 14% 51% 30%	420
July	1st to 10th	Night	2 1 12% 50% 34% 1	410
	11th to 20th	Night	3 1 10% 55% 31%	408
	21st to end	Night	1 6% 50% 39% 3	513
August	1st to 10th	Night	2 1 3 44% 48% 2	627
	11th to 20th	Night	1 1 6% 44% 42% 5%	682
	21st to end	Night	3 2 11% 43% 39% 3	924
September	1st to 10th	Night	3 3 11% 43% 38% 2	840
	11th to 20th	Night	6% 3 12% 36% 38% 5%	840
	21st to end	Night	4 3 15% 37% 35% 5%	840
October	1st to 10th	Night	6% 3 17% 39% 32% 4	840
	11th to 20th	Night	8% 4 15% 39% 29% 5%	812
	21st to end	Night	10% 4 18% 38% 25% 6%	880
November	1st to 10th	Night	13% 6% 17% 41% 19% 5%	820
	11th to 20th	Night	15% 7% 21% 35% 19% 2	840
	21st to end	Night	13% 7% 17% 38% 23% 3	840
December	1st to 10th	Night	14% 6% 20% 35% 22% 3	840
	11th to 20th	Night	18% 11% 18% 33% 19% 2	840
	21st to end	Night	20% 11% 24% 34% 9% 1	924

Page generated at 2026-10-11 02:06:32. Version ac07

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