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 2025-06-10.

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	7% 7% 2 5% 4 3 4 3 4 6% 55%	123825
	Night	9% 7% 2 5% 4 4 4 3 5% 6% 52%	123252
Transparency	Day	29% 5% 9% 21% 21% 14%	123572
	Night	32% 6% 11% 23% 18% 10%	123092
Seeing	Day	11% 10% 20% 25% 22% 12%	15585
	Night	11% 6% 19% 38% 24% 3	24788

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% 6% 10% 6% 5% 5% 4 5% 6% 24%	3639
	11th to 20th	Day	14% 14% 4 6% 3 2 3 2 4 6% 42%	3704
	21st to end	Day	15% 10% 2 6% 3 3 3 2 3 6% 48%	4510
February	1st to 10th	Day	10% 11% 3 7% 5% 6% 5% 4 6% 8% 37%	1800
	11th to 20th	Day	9% 11% 4 7% 6% 6% 5% 4 5% 8% 36%	1795
	21st to end	Day	7% 12% 3 8% 6% 6% 6% 4 4 7% 36%	1650
March	1st to 10th	Day	10% 18% 5% 9% 4 4 3 3 5% 7% 32%	4643
	11th to 20th	Day	8% 14% 3 5% 5% 4 4 3 4 6% 43%	5000
	21st to end	Day	10% 15% 4 9% 6% 5% 5% 4 5% 6% 32%	5695
April	1st to 10th	Day	9% 9% 3 9% 6% 6% 6% 4 5% 6% 37%	2400
	11th to 20th	Day	11% 9% 3 6% 4 3 4 3 6% 7% 44%	2369
	21st to end	Day	7% 6% 2 7% 4 4 3 3 5% 8% 49%	2400
May	1st to 10th	Day	6% 6% 2 4 3 3 3 2 5% 6% 61%	6129
	11th to 20th	Day	4 4 1 4 3 4 4 3 5% 6% 62%	6277
	21st to end	Day	4 3 1 3 3 2 3 3 4 7% 67%	6902
June	1st to 10th	Day	7% 5% 2 5% 4 4 5% 4 6% 7% 51%	2789
	11th to 20th	Day	3 3 1 3 3 3 3 3 4 7% 66%	2660
	21st to end	Day	4 2 1 2 2 2 3 2 4 5% 74%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 2 3 86%	4420
	11th to 20th	Day	2 2 1 3 3 2 3 2 4 4 76%	4420
	21st to end	Day	1 1 1 1 1 2 2 2 4 3 82%	4706
August	1st to 10th	Day	3 2 1 3 2 2 3 3 5% 5% 70%	4091
	11th to 20th	Day	1 1 1 1 2 2 2 3 6% 79%	3937
	21st to end	Day	2 1 1 2 1 2 2 2 3 5% 80%	4180
September	1st to 10th	Day	1 1 2 2 2 2 2 4 4 81%	2280
	11th to 20th	Day	4 2 1 3 3 3 3 3 4 6% 68%	2280
	21st to end	Day	4 3 1 4 3 2 3 2 4 7% 67%	2033
October	1st to 10th	Day	4 3 1 3 2 2 3 2 3 5% 73%	3180
	11th to 20th	Day	6% 3 1 3 3 3 3 4 6% 10% 58%	3161
	21st to end	Day	9% 6% 1 6% 5% 5% 5% 4 6% 8% 45%	3399
November	1st to 10th	Day	13% 9% 3 6% 4 5% 4 3 4 7% 41%	1764
	11th to 20th	Day	13% 8% 3 7% 6% 4 5% 5% 8% 8% 32%	1700
	21st to end	Day	9% 9% 3 9% 5% 5% 5% 4 5% 8% 39%	1600
December	1st to 10th	Day	6% 7% 2 7% 4 4 4 4 5% 8% 48%	2620
	11th to 20th	Day	19% 12% 4 8% 6% 5% 5% 4 6% 9% 21%	3028
	21st to end	Day	15% 12% 5% 11% 7% 7% 6% 5% 6% 7% 19%	4004
January	1st to 10th	Night	13% 13% 4 9% 7% 6% 6% 5% 5% 8% 25%	6306
	11th to 20th	Night	12% 12% 2 5% 4 4 4 2 4 5% 46%	6258
	21st to end	Night	14% 10% 3 6% 4 4 4 3 4 5% 43%	6468
February	1st to 10th	Night	10% 10% 3 6% 5% 6% 5% 4 5% 7% 39%	2600
	11th to 20th	Night	11% 11% 3 7% 4 4 4 4 5% 7% 41%	2492
	21st to end	Night	8% 9% 3 7% 5% 5% 5% 4 5% 7% 40%	1980
March	1st to 10th	Night	8% 15% 4 8% 5% 4 4 4 5% 7% 36%	5249
	11th to 20th	Night	9% 10% 2 5% 4 4 3 4 6% 8% 46%	5000
	21st to end	Night	10% 12% 4 8% 6% 5% 5% 4 5% 7% 33%	5280
April	1st to 10th	Night	10% 10% 3 6% 5% 5% 4 3 6% 8% 41%	2000
	11th to 20th	Night	8% 9% 2 6% 4 4 3 3 4 6% 50%	1979
	21st to end	Night	9% 6% 2 6% 3 3 3 3 5% 8% 52%	2000
May	1st to 10th	Night	6% 4 2 4 3 3 3 3 3 5% 65%	3835
	11th to 20th	Night	4 4 1 4 3 3 3 3 5% 5% 64%	3616
	21st to end	Night	4 3 1 2 2 2 3 2 3 5% 72%	3972
June	1st to 10th	Night	8% 6% 2 5% 3 4 3 3 5% 8% 54%	1595
	11th to 20th	Night	5% 3 1 3 2 3 3 2 4 5% 69%	1520
	21st to end	Night	3 3 1 2 3 2 2 2 3 4 76%	1520
July	1st to 10th	Night	1 2 1 1 1 2 2 3 87%	2540
	11th to 20th	Night	1 2 1 3 2 2 2 2 3 3 78%	2540
	21st to end	Night	1 1 2 1 1 2 2 3 4 83%	2844
August	1st to 10th	Night	2 2 1 2 2 3 3 2 4 4 74%	2848
	11th to 20th	Night	1 1 1 1 2 2 2 3 4 82%	2903
	21st to end	Night	3 2 1 2 2 1 2 1 2 3 80%	3498
September	1st to 10th	Night	2 1 1 2 1 1 1 1 3 4 84%	1900
	11th to 20th	Night	5% 3 1 3 2 2 3 2 5% 5% 70%	1900
	21st to end	Night	4 3 1 3 3 2 2 2 3 6% 70%	2144
October	1st to 10th	Night	3 2 1 3 2 2 3 2 3 3 78%	3800
	11th to 20th	Night	6% 4 1 4 3 3 3 2 4 7% 63%	3777
	21st to end	Night	6% 5% 2 4 3 4 5% 4 7% 9% 53%	4167
November	1st to 10th	Night	11% 8% 2 5% 5% 4 4 4 5% 8% 43%	2535
	11th to 20th	Night	14% 7% 2 6% 4 5% 5% 4 6% 9% 37%	2698
	21st to end	Night	10% 9% 2 5% 4 5% 4 4 6% 8% 44%	2800
December	1st to 10th	Night	8% 5% 1 4 3 4 4 3 6% 9% 52%	4560
	11th to 20th	Night	18% 11% 4 8% 6% 5% 6% 4 6% 8% 24%	5176
	21st to end	Night	18% 12% 4 10% 6% 6% 5% 3 5% 7% 24%	6952

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	56% 11% 11% 17% 6%	3639
	11th to 20th	Day	44% 5% 9% 26% 13% 2	3704
	21st to end	Day	37% 7% 10% 15% 22% 8%	4510
February	1st to 10th	Day	43% 7% 17% 20% 12% 1	1800
	11th to 20th	Day	44% 7% 14% 22% 12% 2	1804
	21st to end	Day	45% 7% 15% 18% 11% 4	1650
March	1st to 10th	Day	48% 9% 8% 24% 9% 3	4643
	11th to 20th	Day	39% 7% 13% 23% 17%	5000
	21st to end	Day	49% 9% 13% 20% 8% 1	5695
April	1st to 10th	Day	46% 6% 13% 19% 13% 2	2400
	11th to 20th	Day	37% 5% 13% 23% 17% 5%	2372
	21st to end	Day	32% 6% 16% 26% 18% 3	2400
May	1st to 10th	Day	24% 4 7% 26% 31% 8%	6129
	11th to 20th	Day	24% 4 9% 23% 31% 9%	6280
	21st to end	Day	18% 4 9% 35% 29% 4	6904
June	1st to 10th	Day	29% 7% 12% 26% 21% 5%	2789
	11th to 20th	Day	19% 4 9% 27% 32% 9%	2660
	21st to end	Day	14% 3 5% 24% 32% 22%	2660
July	1st to 10th	Day	7% 2 3 11% 17% 61%	4351
	11th to 20th	Day	13% 3 3 11% 20% 51%	4345
	21st to end	Day	9% 2 3 12% 32% 42%	4557
August	1st to 10th	Day	15% 4 4 11% 24% 43%	4076
	11th to 20th	Day	8% 3 3 20% 39% 27%	3976
	21st to end	Day	10% 2 3 22% 35% 28%	4179
September	1st to 10th	Day	9% 3 4 14% 30% 41%	2280
	11th to 20th	Day	18% 4 8% 19% 31% 20%	2280
	21st to end	Day	18% 4 8% 22% 28% 20%	2033
October	1st to 10th	Day	17% 3 7% 16% 30% 27%	3180
	11th to 20th	Day	22% 4 10% 36% 22% 6%	3161
	21st to end	Day	36% 6% 10% 23% 19% 6%	3399
November	1st to 10th	Day	41% 7% 12% 22% 15% 4	1764
	11th to 20th	Day	45% 8% 16% 16% 14% 1	1700
	21st to end	Day	42% 6% 13% 19% 18% 3	1600
December	1st to 10th	Day	34% 7% 10% 26% 21% 3	2620
	11th to 20th	Day	58% 8% 15% 15% 5%	3028
	21st to end	Day	57% 13% 11% 14% 4	4004
January	1st to 10th	Night	52% 11% 14% 17% 5% 1	6306
	11th to 20th	Night	38% 8% 10% 25% 16% 3	6258
	21st to end	Night	42% 6% 8% 15% 19% 9%	6468
February	1st to 10th	Night	42% 8% 14% 22% 12% 2	2600
	11th to 20th	Night	41% 7% 15% 22% 13% 2	2494
	21st to end	Night	39% 8% 17% 20% 13% 3	1980
March	1st to 10th	Night	44% 8% 9% 25% 12% 3	5249
	11th to 20th	Night	34% 8% 13% 29% 16%	5000
	21st to end	Night	47% 9% 15% 20% 8% 1	5280
April	1st to 10th	Night	40% 8% 16% 22% 11% 2	2000
	11th to 20th	Night	35% 6% 16% 23% 16% 4	1979
	21st to end	Night	31% 7% 20% 27% 13% 2	2000
May	1st to 10th	Night	22% 5% 10% 27% 31% 5%	3832
	11th to 20th	Night	21% 5% 12% 29% 27% 6%	3616
	21st to end	Night	16% 5% 14% 44% 20% 2	3972
June	1st to 10th	Night	30% 6% 15% 32% 15% 3	1595
	11th to 20th	Night	19% 6% 10% 32% 27% 6%	1520
	21st to end	Night	13% 3 8% 29% 33% 15%	1520
July	1st to 10th	Night	6% 2 4 12% 20% 56%	2500
	11th to 20th	Night	13% 2 3 10% 23% 49%	2492
	21st to end	Night	7% 2 5% 13% 35% 38%	2755
August	1st to 10th	Night	14% 2 4 15% 26% 39%	2839
	11th to 20th	Night	7% 3 4 24% 39% 23%	2930
	21st to end	Night	11% 2 5% 28% 27% 26%	3498
September	1st to 10th	Night	7% 2 4 16% 29% 41%	1900
	11th to 20th	Night	16% 4 7% 22% 31% 19%	1900
	21st to end	Night	17% 4 7% 24% 25% 23%	2144
October	1st to 10th	Night	15% 3 6% 16% 31% 29%	3800
	11th to 20th	Night	21% 4 12% 35% 21% 7%	3777
	21st to end	Night	27% 5% 14% 29% 19% 7%	4167
November	1st to 10th	Night	38% 8% 13% 20% 17% 4	2535
	11th to 20th	Night	41% 9% 15% 18% 15% 1	2698
	21st to end	Night	37% 8% 15% 18% 17% 4	2800
December	1st to 10th	Night	29% 6% 13% 29% 22% 2	4560
	11th to 20th	Night	56% 8% 11% 19% 6%	5176
	21st to end	Night	55% 11% 11% 17% 5% 1	6952

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% 24% 25% 8% 4	200
	11th to 20th	Day	21% 11% 21% 24% 12% 12%	225
	21st to end	Day	17% 11% 17% 23% 23% 8%	440
February	1st to 10th	Day	16% 15% 21% 23% 19% 7%	400
	11th to 20th	Day	17% 17% 23% 24% 15% 4	415
	21st to end	Day	16% 13% 24% 31% 12% 4	414
March	1st to 10th	Day	21% 18% 27% 21% 12% 2	500
	11th to 20th	Day	19% 15% 25% 21% 17% 3	500
	21st to end	Day	22% 17% 21% 26% 12% 2	550
April	1st to 10th	Day	15% 17% 25% 24% 13% 5%	500
	11th to 20th	Day	18% 14% 22% 23% 15% 8%	492
	21st to end	Day	8% 16% 26% 24% 19% 8%	500
May	1st to 10th	Day	12% 14% 25% 27% 18% 5%	503
	11th to 20th	Day	15% 12% 23% 23% 15% 12%	528
	21st to end	Day	10% 9% 18% 27% 22% 14%	573
June	1st to 10th	Day	7% 11% 19% 25% 22% 16%	527
	11th to 20th	Day	6% 16% 24% 21% 21% 11%	490
	21st to end	Day	2 7% 17% 28% 27% 19%	490
July	1st to 10th	Day	4 3 18% 31% 27% 16%	486
	11th to 20th	Day	1 2 20% 29% 28% 19%	484
	21st to end	Day	2 2 14% 28% 32% 22%	531
August	1st to 10th	Day	2 1 17% 26% 30% 23%	487
	11th to 20th	Day	2 5% 14% 25% 31% 23%	477
	21st to end	Day	3 4 16% 28% 29% 19%	539
September	1st to 10th	Day	1 4 19% 23% 36% 16%	490
	11th to 20th	Day	6% 7% 18% 28% 25% 16%	490
	21st to end	Day	6% 6% 20% 26% 30% 12%	490
October	1st to 10th	Day	8% 9% 17% 25% 23% 18%	490
	11th to 20th	Day	11% 10% 16% 23% 28% 13%	490
	21st to end	Day	12% 10% 18% 27% 20% 13%	514
November	1st to 10th	Day	16% 10% 18% 29% 18% 9%	300
	11th to 20th	Day	15% 8% 20% 24% 27% 7%	250
	21st to end	Day	14% 7% 19% 27% 26% 9%	200
December	1st to 10th	Day	15% 11% 18% 26% 17% 13%	200
	11th to 20th	Day	26% 11% 17% 24% 18% 6%	200
	21st to end	Day	14% 16% 24% 24% 20% 2	220
January	1st to 10th	Night	17% 8% 23% 32% 17% 3	800
	11th to 20th	Night	15% 9% 23% 31% 19% 3	800
	21st to end	Night	15% 5% 22% 36% 20% 4	880
February	1st to 10th	Night	13% 7% 24% 38% 17% 1	800
	11th to 20th	Night	15% 8% 23% 35% 17% 2	784
	21st to end	Night	11% 10% 24% 40% 14% 1	660
March	1st to 10th	Night	15% 13% 26% 31% 13% 2	800
	11th to 20th	Night	16% 9% 20% 35% 19% 2	800
	21st to end	Night	16% 11% 25% 33% 15%	880
April	1st to 10th	Night	12% 10% 24% 37% 17% 1	800
	11th to 20th	Night	11% 8% 27% 34% 17% 3	791
	21st to end	Night	11% 8% 23% 37% 20% 2	800
May	1st to 10th	Night	8% 5% 26% 39% 20% 1	491
	11th to 20th	Night	11% 5% 21% 39% 23% 2	394
	21st to end	Night	10% 4 21% 41% 24% 1	433
June	1st to 10th	Night	9% 4 17% 43% 26% 1	399
	11th to 20th	Night	6% 6% 24% 45% 19% 1	380
	21st to end	Night	4 1 12% 52% 30%	380
July	1st to 10th	Night	2 1 11% 51% 36% 1	370
	11th to 20th	Night	2 1 10% 54% 33%	368
	21st to end	Night	1 5% 51% 40% 3	463
August	1st to 10th	Night	2 1 3 45% 47% 2	567
	11th to 20th	Night	2 1 6% 43% 43% 5%	616
	21st to end	Night	3 1 10% 42% 41% 3	836
September	1st to 10th	Night	1 3 11% 43% 40% 3	760
	11th to 20th	Night	6% 3 12% 35% 39% 6%	760
	21st to end	Night	5% 3 15% 37% 34% 5%	760
October	1st to 10th	Night	6% 2 17% 40% 32% 4	760
	11th to 20th	Night	8% 4 15% 38% 31% 5%	760
	21st to end	Night	9% 5% 18% 37% 25% 6%	836
November	1st to 10th	Night	13% 6% 17% 41% 18% 5%	780
	11th to 20th	Night	15% 7% 22% 35% 19% 2	800
	21st to end	Night	13% 7% 16% 37% 23% 3	800
December	1st to 10th	Night	15% 6% 20% 34% 22% 4	800
	11th to 20th	Night	18% 10% 18% 33% 19% 2	800
	21st to end	Night	20% 11% 24% 35% 9% 1	880

Page generated at 2025-06-07 07:28:19. Version ac07

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