Katepwa Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Katepwa Lake clear sky chart from 2005-11-06 to 2025-09-19.

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	9% 8% 3 9% 5% 5% 5% 4 6% 8% 37%	130749
	Night	8% 9% 4 9% 6% 5% 5% 4 6% 7% 35%	127041
Transparency	Day	44% 5% 16% 25% 9% 1	130462
	Night	47% 5% 15% 23% 9% 1	126908
Seeing	Day	13% 8% 28% 29% 16% 4	17409
	Night	13% 7% 29% 35% 14% 2	26752

By Month

Percentage Cloud Cover NW (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	5% 14% 6% 17% 9% 9% 7% 4 7% 7% 14%	3221
	11th to 20th	Day	4 8% 4 12% 10% 10% 7% 9% 12% 9% 16%	3616
	21st to end	Day	5% 13% 6% 14% 8% 6% 5% 3 5% 6% 30%	4004
February	1st to 10th	Day	7% 14% 5% 15% 7% 6% 8% 6% 7% 6% 19%	1600
	11th to 20th	Day	7% 10% 6% 11% 7% 7% 8% 6% 7% 7% 25%	1750
	21st to end	Day	5% 9% 5% 11% 10% 8% 7% 5% 8% 8% 23%	1650
March	1st to 10th	Day	6% 12% 6% 16% 7% 5% 5% 4 5% 8% 26%	4500
	11th to 20th	Day	7% 13% 6% 17% 7% 6% 4 3 5% 6% 26%	4648
	21st to end	Day	10% 11% 4 13% 6% 5% 5% 4 6% 7% 29%	5969
April	1st to 10th	Day	7% 9% 3 7% 6% 5% 6% 4 7% 8% 37%	2400
	11th to 20th	Day	14% 16% 4 9% 5% 5% 4 4 4 7% 28%	2445
	21st to end	Day	14% 8% 2 8% 4 5% 5% 4 6% 7% 37%	2715
May	1st to 10th	Day	15% 7% 2 5% 4 3 4 4 6% 7% 43%	6340
	11th to 20th	Day	17% 8% 3 7% 5% 4 5% 4 7% 9% 32%	6298
	21st to end	Day	11% 7% 2 5% 4 4 4 4 5% 7% 47%	7329
June	1st to 10th	Day	15% 6% 2 7% 5% 4 6% 4 7% 8% 37%	3029
	11th to 20th	Day	18% 7% 3 7% 6% 6% 6% 4 7% 7% 29%	3200
	21st to end	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 8% 40%	3200
July	1st to 10th	Day	5% 4 2 5% 4 5% 6% 5% 7% 10% 45%	7240
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 44%	6444
	21st to end	Day	6% 4 2 5% 3 4 4 3 6% 9% 53%	6898
August	1st to 10th	Day	8% 6% 2 6% 5% 4 5% 4 7% 8% 45%	4552
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 4 7% 11% 47%	4483
	21st to end	Day	11% 5% 2 5% 3 4 4 3 5% 7% 51%	4431
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 3 4 8% 49%	2400
	11th to 20th	Day	13% 8% 3 6% 4 4 3 3 6% 8% 40%	2327
	21st to end	Day	13% 7% 2 4 4 2 4 3 4 7% 49%	2090
October	1st to 10th	Day	11% 9% 3 6% 4 4 5% 3 6% 7% 43%	3206
	11th to 20th	Day	7% 7% 3 5% 3 3 4 3 6% 11% 49%	2939
	21st to end	Day	8% 10% 5% 9% 4 4 4 4 6% 7% 38%	3091
November	1st to 10th	Day	15% 15% 4 10% 7% 5% 4 3 4 5% 28%	1684
	11th to 20th	Day	7% 15% 5% 14% 8% 5% 4 3 5% 6% 26%	1545
	21st to end	Day	9% 16% 6% 11% 6% 6% 5% 4 5% 5% 27%	1400
December	1st to 10th	Day	6% 12% 5% 16% 11% 8% 7% 4 5% 5% 23%	2290
	11th to 20th	Day	6% 17% 7% 16% 8% 6% 7% 5% 5% 6% 18%	2639
	21st to end	Day	4 9% 5% 14% 7% 5% 5% 4 4 4 40%	3176
January	1st to 10th	Night	4 13% 5% 16% 11% 7% 7% 5% 7% 8% 18%	6711
	11th to 20th	Night	5% 8% 4 13% 10% 10% 9% 8% 9% 6% 17%	6302
	21st to end	Night	5% 12% 6% 14% 9% 5% 5% 4 6% 7% 29%	6974
February	1st to 10th	Night	8% 12% 4 11% 7% 7% 7% 5% 7% 8% 23%	2800
	11th to 20th	Night	4 10% 5% 11% 8% 7% 7% 5% 7% 7% 29%	2554
	21st to end	Night	3 9% 4 11% 8% 7% 6% 4 7% 8% 32%	1980
March	1st to 10th	Night	6% 12% 6% 13% 6% 5% 6% 4 6% 9% 26%	5374
	11th to 20th	Night	6% 12% 5% 11% 9% 6% 5% 5% 5% 7% 29%	5320
	21st to end	Night	8% 13% 5% 12% 7% 6% 5% 4 7% 8% 26%	4984
April	1st to 10th	Night	6% 9% 3 5% 5% 5% 4 4 7% 8% 44%	2000
	11th to 20th	Night	14% 11% 4 8% 5% 4 5% 4 6% 6% 34%	1905
	21st to end	Night	14% 8% 3 7% 5% 5% 5% 5% 6% 6% 36%	1683
May	1st to 10th	Night	13% 7% 2 6% 4 3 5% 4 5% 7% 46%	3640
	11th to 20th	Night	16% 8% 3 7% 4 5% 5% 5% 6% 7% 35%	3618
	21st to end	Night	14% 5% 1 5% 3 3 4 3 5% 7% 49%	3566
June	1st to 10th	Night	12% 6% 2 5% 5% 4 3 5% 6% 7% 46%	1368
	11th to 20th	Night	17% 7% 2 5% 4 5% 5% 5% 5% 6% 39%	1200
	21st to end	Night	12% 6% 2 5% 4 3 5% 3 7% 8% 47%	1200
July	1st to 10th	Night	7% 4 2 5% 4 4 5% 5% 8% 10% 46%	2720
	11th to 20th	Night	10% 4 2 5% 4 4 4 4 6% 8% 49%	3514
	21st to end	Night	5% 3 1 4 2 3 3 4 5% 8% 62%	3968
August	1st to 10th	Night	7% 5% 2 5% 3 4 4 4 6% 8% 53%	2608
	11th to 20th	Night	6% 3 1 5% 3 5% 5% 4 7% 10% 51%	2576
	21st to end	Night	7% 4 2 4 4 4 4 4 6% 9% 53%	3474
September	1st to 10th	Night	9% 5% 2 6% 3 4 4 3 5% 6% 52%	2000
	11th to 20th	Night	12% 7% 2 5% 4 4 5% 4 6% 8% 45%	2029
	21st to end	Night	11% 6% 2 5% 4 3 4 4 6% 6% 49%	2090
October	1st to 10th	Night	11% 8% 2 6% 3 4 4 3 5% 7% 47%	3760
	11th to 20th	Night	6% 6% 2 5% 3 4 5% 4 7% 10% 46%	3957
	21st to end	Night	8% 10% 4 8% 4 3 4 3 6% 8% 43%	4467
November	1st to 10th	Night	15% 14% 4 9% 6% 4 4 3 5% 5% 30%	2610
	11th to 20th	Night	9% 14% 5% 12% 8% 5% 5% 4 5% 5% 28%	2855
	21st to end	Night	9% 13% 5% 11% 7% 6% 5% 4 6% 6% 29%	3000
December	1st to 10th	Night	7% 15% 7% 14% 8% 9% 7% 5% 5% 5% 17%	4900
	11th to 20th	Night	7% 14% 5% 13% 8% 7% 7% 5% 7% 8% 19%	5568
	21st to end	Night	4 7% 3 13% 9% 7% 6% 4 5% 6% 37%	7766

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	68% 5% 12% 10% 5%	3221
	11th to 20th	Day	55% 6% 15% 16% 7%	3640
	21st to end	Day	56% 3 17% 20% 4	4004
February	1st to 10th	Day	62% 6% 12% 12% 7% 1	1600
	11th to 20th	Day	55% 5% 10% 18% 12%	1759
	21st to end	Day	55% 6% 13% 17% 9%	1650
March	1st to 10th	Day	56% 5% 16% 17% 6%	4500
	11th to 20th	Day	59% 5% 14% 16% 5%	4649
	21st to end	Day	53% 5% 12% 18% 11% 1	5969
April	1st to 10th	Day	42% 7% 17% 25% 10%	2400
	11th to 20th	Day	56% 5% 12% 17% 8% 2	2445
	21st to end	Day	45% 5% 17% 24% 8% 1	2715
May	1st to 10th	Day	39% 5% 13% 25% 17% 1	6340
	11th to 20th	Day	47% 6% 13% 24% 10%	6302
	21st to end	Day	35% 6% 10% 28% 20% 1	7329
June	1st to 10th	Day	43% 6% 14% 26% 10% 1	3029
	11th to 20th	Day	51% 7% 15% 19% 9% 1	3200
	21st to end	Day	39% 8% 19% 26% 9%	3200
July	1st to 10th	Day	32% 6% 26% 28% 8%	7161
	11th to 20th	Day	35% 5% 19% 34% 6%	6365
	21st to end	Day	28% 4 21% 35% 12% 1	6705
August	1st to 10th	Day	35% 6% 18% 28% 12% 1	4536
	11th to 20th	Day	30% 5% 22% 37% 5%	4525
	21st to end	Day	33% 5% 15% 37% 9% 1	4430
September	1st to 10th	Day	35% 4 14% 33% 13% 1	2400
	11th to 20th	Day	41% 5% 16% 25% 11% 1	2327
	21st to end	Day	35% 4 15% 32% 12% 2	2090
October	1st to 10th	Day	40% 4 18% 29% 8% 1	3206
	11th to 20th	Day	32% 2 18% 38% 9% 1	2939
	21st to end	Day	45% 4 18% 26% 7%	3091
November	1st to 10th	Day	60% 4 15% 14% 7%	1684
	11th to 20th	Day	60% 6% 14% 14% 6% 1	1545
	21st to end	Day	60% 5% 15% 16% 5%	1400
December	1st to 10th	Day	63% 6% 15% 13% 4	2290
	11th to 20th	Day	67% 4 17% 11% 2	2640
	21st to end	Day	49% 4 9% 24% 10% 4	3176
January	1st to 10th	Night	62% 5% 12% 16% 4	6711
	11th to 20th	Night	60% 6% 14% 15% 5%	6340
	21st to end	Night	54% 6% 20% 16% 3	6974
February	1st to 10th	Night	56% 6% 12% 17% 8% 1	2800
	11th to 20th	Night	51% 6% 12% 20% 11% 1	2555
	21st to end	Night	48% 5% 13% 25% 8%	1980
March	1st to 10th	Night	53% 5% 22% 15% 5%	5374
	11th to 20th	Night	53% 6% 17% 19% 6%	5320
	21st to end	Night	54% 5% 10% 21% 9%	4984
April	1st to 10th	Night	36% 5% 16% 26% 17% 1	2000
	11th to 20th	Night	49% 5% 10% 23% 12% 2	1905
	21st to end	Night	46% 5% 13% 22% 13% 1	1683
May	1st to 10th	Night	38% 4 13% 26% 18% 1	3640
	11th to 20th	Night	46% 5% 15% 20% 12% 2	3618
	21st to end	Night	33% 6% 10% 27% 23% 1	3566
June	1st to 10th	Night	36% 7% 14% 28% 13% 2	1368
	11th to 20th	Night	44% 6% 14% 22% 12% 1	1200
	21st to end	Night	36% 6% 19% 30% 9% 1	1200
July	1st to 10th	Night	31% 6% 26% 31% 6%	2690
	11th to 20th	Night	32% 5% 18% 36% 9% 1	3470
	21st to end	Night	22% 4 25% 31% 15% 3	3856
August	1st to 10th	Night	28% 5% 22% 30% 14% 1	2600
	11th to 20th	Night	27% 5% 21% 38% 9% 1	2600
	21st to end	Night	28% 4 18% 38% 11% 1	3474
September	1st to 10th	Night	33% 5% 12% 31% 17% 2	2000
	11th to 20th	Night	37% 6% 16% 27% 12% 1	2029
	21st to end	Night	35% 4 14% 30% 15% 2	2090
October	1st to 10th	Night	37% 4 16% 32% 9% 3	3760
	11th to 20th	Night	33% 4 15% 35% 11% 1	3957
	21st to end	Night	40% 4 14% 32% 10%	4467
November	1st to 10th	Night	57% 4 12% 18% 8% 1	2610
	11th to 20th	Night	58% 5% 17% 15% 5%	2855
	21st to end	Night	55% 6% 16% 18% 4	3000
December	1st to 10th	Night	69% 7% 10% 10% 3	4900
	11th to 20th	Night	62% 5% 16% 13% 4	5566
	21st to end	Night	48% 4 9% 22% 13% 3	7766

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	12% 10% 30% 30% 13% 4	254
	11th to 20th	Day	9% 7% 35% 34% 14% 1	300
	21st to end	Day	15% 8% 33% 27% 15% 1	330
February	1st to 10th	Day	14% 12% 29% 31% 13% 1	300
	11th to 20th	Day	9% 7% 30% 33% 16% 5%	300
	21st to end	Day	8% 5% 25% 39% 18% 4	249
March	1st to 10th	Day	12% 7% 34% 30% 15% 3	300
	11th to 20th	Day	13% 9% 28% 30% 16% 4	340
	21st to end	Day	17% 9% 30% 28% 14% 3	550
April	1st to 10th	Day	10% 12% 38% 30% 9% 2	500
	11th to 20th	Day	21% 14% 30% 25% 9% 2	563
	21st to end	Day	15% 9% 27% 32% 16% 1	700
May	1st to 10th	Day	14% 9% 28% 31% 16% 3	703
	11th to 20th	Day	15% 8% 29% 26% 16% 7%	725
	21st to end	Day	16% 5% 27% 28% 17% 7%	789
June	1st to 10th	Day	15% 13% 26% 25% 16% 5%	730
	11th to 20th	Day	18% 12% 29% 26% 12% 3	730
	21st to end	Day	14% 8% 24% 30% 18% 6%	730
July	1st to 10th	Day	7% 5% 24% 33% 24% 7%	721
	11th to 20th	Day	9% 6% 27% 30% 21% 7%	718
	21st to end	Day	7% 6% 26% 32% 20% 9%	794
August	1st to 10th	Day	10% 6% 21% 35% 22% 6%	726
	11th to 20th	Day	8% 4 23% 33% 24% 7%	715
	21st to end	Day	12% 7% 21% 35% 20% 6%	649
September	1st to 10th	Day	13% 9% 33% 25% 16% 5%	530
	11th to 20th	Day	20% 8% 28% 26% 14% 4	473
	21st to end	Day	15% 11% 31% 28% 13% 3	300
October	1st to 10th	Day	21% 11% 25% 20% 20% 3	300
	11th to 20th	Day	17% 10% 31% 25% 12% 4	300
	21st to end	Day	15% 12% 33% 27% 10% 3	330
November	1st to 10th	Day	21% 9% 30% 25% 11% 4	300
	11th to 20th	Day	17% 10% 36% 29% 8%	300
	21st to end	Day	14% 8% 37% 30% 9% 2	300
December	1st to 10th	Day	12% 7% 34% 31% 13% 4	300
	11th to 20th	Day	13% 8% 43% 28% 5% 2	300
	21st to end	Day	13% 4 30% 32% 17% 4	260
January	1st to 10th	Night	10% 10% 31% 34% 13% 2	1000
	11th to 20th	Night	15% 11% 32% 33% 8% 1	1000
	21st to end	Night	13% 12% 34% 31% 9% 1	1100
February	1st to 10th	Night	14% 8% 31% 32% 14% 2	1000
	11th to 20th	Night	9% 6% 31% 39% 12% 3	809
	21st to end	Night	6% 6% 24% 41% 19% 4	660
March	1st to 10th	Night	12% 7% 29% 36% 14% 2	800
	11th to 20th	Night	10% 7% 31% 36% 15% 1	795
	21st to end	Night	15% 4 28% 36% 16% 2	660
April	1st to 10th	Night	10% 8% 31% 36% 14% 1	600
	11th to 20th	Night	19% 8% 30% 34% 9% 1	593
	21st to end	Night	18% 6% 31% 35% 11% 1	600
May	1st to 10th	Night	13% 6% 29% 35% 15% 1	600
	11th to 20th	Night	17% 5% 27% 34% 15% 1	591
	21st to end	Night	20% 5% 24% 33% 17% 2	650
June	1st to 10th	Night	16% 5% 28% 35% 15% 2	568
	11th to 20th	Night	20% 7% 26% 36% 11% 1	400
	21st to end	Night	14% 4 25% 38% 17% 1	400
July	1st to 10th	Night	9% 3 23% 41% 22% 2	390
	11th to 20th	Night	10% 3 25% 41% 20% 1	549
	21st to end	Night	6% 4 21% 42% 23% 3	657
August	1st to 10th	Night	8% 3 22% 43% 22% 3	597
	11th to 20th	Night	9% 2 17% 45% 26% 2	594
	21st to end	Night	9% 5% 24% 40% 21% 1	660
September	1st to 10th	Night	11% 5% 26% 36% 21% 2	600
	11th to 20th	Night	14% 6% 23% 41% 15% 1	594
	21st to end	Night	12% 6% 29% 38% 13% 1	570
October	1st to 10th	Night	20% 7% 21% 35% 16% 1	733
	11th to 20th	Night	14% 8% 29% 36% 13% 1	862
	21st to end	Night	16% 10% 31% 34% 8% 1	1045
November	1st to 10th	Night	20% 9% 29% 32% 9% 1	975
	11th to 20th	Night	16% 10% 35% 28% 9% 2	1000
	21st to end	Night	14% 10% 35% 33% 6% 1	1000
December	1st to 10th	Night	12% 7% 34% 32% 13% 3	1000
	11th to 20th	Night	12% 11% 32% 33% 10% 2	1000
	21st to end	Night	12% 5% 30% 35% 15% 3	1100

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