Walloper Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walloper Lake clear sky chart from 2005-11-06 to 2026-02-16.

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% 10% 4 10% 6% 6% 6% 5% 6% 8% 33%	134068
	Night	5% 10% 4 10% 6% 6% 6% 5% 7% 8% 34%	135459
Transparency	Day	44% 7% 15% 21% 10% 2	133782
	Night	44% 7% 15% 22% 10% 1	135323
Seeing	Day	18% 16% 26% 23% 13% 3	17144
	Night	14% 16% 25% 27% 15% 3	25657

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	4 15% 7% 16% 8% 7% 7% 5% 7% 7% 16%	4125
	11th to 20th	Day	3 10% 4 8% 6% 5% 6% 5% 8% 8% 36%	4376
	21st to end	Day	2 13% 5% 12% 7% 7% 5% 5% 6% 9% 29%	5186
February	1st to 10th	Day	5% 16% 5% 13% 8% 6% 5% 6% 7% 7% 21%	1748
	11th to 20th	Day	4 14% 6% 12% 5% 5% 6% 6% 5% 7% 29%	1801
	21st to end	Day	3 15% 7% 14% 8% 8% 6% 5% 7% 6% 22%	1580
March	1st to 10th	Day	2 9% 4 12% 8% 8% 9% 6% 10% 9% 24%	4518
	11th to 20th	Day	2 9% 5% 11% 7% 7% 7% 5% 7% 8% 32%	4862
	21st to end	Day	5% 15% 5% 13% 8% 7% 7% 5% 6% 7% 21%	5834
April	1st to 10th	Day	6% 14% 5% 12% 10% 9% 6% 5% 6% 7% 19%	2400
	11th to 20th	Day	6% 15% 6% 12% 8% 6% 6% 5% 5% 8% 23%	2377
	21st to end	Day	7% 15% 5% 11% 7% 6% 6% 5% 6% 8% 24%	2795
May	1st to 10th	Day	6% 12% 5% 8% 5% 4 5% 3 4 6% 42%	6320
	11th to 20th	Day	9% 13% 5% 12% 7% 7% 6% 5% 7% 9% 20%	6277
	21st to end	Day	10% 13% 5% 12% 6% 6% 5% 4 6% 8% 26%	6903
June	1st to 10th	Day	16% 11% 3 8% 6% 6% 5% 5% 6% 7% 26%	3163
	11th to 20th	Day	16% 13% 5% 9% 7% 6% 6% 4 5% 6% 22%	3200
	21st to end	Day	11% 8% 3 8% 7% 5% 6% 5% 7% 8% 33%	3200
July	1st to 10th	Day	7% 6% 2 6% 5% 5% 5% 4 5% 6% 50%	6829
	11th to 20th	Day	6% 5% 2 5% 4 4 4 4 6% 7% 54%	6716
	21st to end	Day	6% 5% 2 5% 4 4 4 4 6% 8% 50%	6874
August	1st to 10th	Day	4 3 2 5% 5% 5% 6% 4 7% 7% 54%	4541
	11th to 20th	Day	4 5% 2 7% 7% 7% 7% 5% 8% 8% 41%	4393
	21st to end	Day	9% 6% 2 7% 4 5% 5% 5% 7% 8% 42%	4444
September	1st to 10th	Day	9% 7% 2 6% 4 4 4 3 6% 7% 48%	2400
	11th to 20th	Day	11% 8% 3 7% 5% 5% 4 4 5% 6% 41%	2400
	21st to end	Day	12% 9% 3 8% 5% 5% 5% 5% 6% 8% 34%	2144
October	1st to 10th	Day	7% 9% 3 7% 5% 5% 5% 4 6% 9% 40%	3280
	11th to 20th	Day	12% 13% 4 8% 4 5% 5% 4 6% 8% 33%	3205
	21st to end	Day	7% 13% 4 10% 5% 6% 5% 5% 7% 8% 30%	3200
November	1st to 10th	Day	10% 14% 4 13% 8% 6% 5% 4 4 6% 25%	1688
	11th to 20th	Day	5% 15% 4 8% 7% 7% 6% 5% 8% 7% 27%	1680
	21st to end	Day	7% 15% 4 10% 8% 6% 7% 5% 6% 8% 23%	1582
December	1st to 10th	Day	4 11% 4 10% 7% 7% 7% 5% 7% 8% 30%	2360
	11th to 20th	Day	4 15% 6% 13% 8% 7% 7% 6% 8% 8% 19%	2424
	21st to end	Day	4 14% 5% 13% 8% 8% 8% 5% 8% 8% 19%	3243
January	1st to 10th	Night	4 15% 6% 15% 9% 8% 7% 5% 7% 7% 17%	8770
	11th to 20th	Night	3 9% 4 10% 6% 6% 6% 4 6% 9% 37%	8506
	21st to end	Night	3 10% 4 12% 6% 6% 7% 5% 7% 7% 32%	8994
February	1st to 10th	Night	6% 15% 5% 13% 8% 6% 6% 5% 6% 7% 24%	2868
	11th to 20th	Night	4 12% 5% 11% 7% 6% 6% 4 6% 7% 32%	2597
	21st to end	Night	3 11% 6% 16% 8% 7% 6% 5% 6% 8% 25%	2049
March	1st to 10th	Night	2 8% 4 10% 7% 7% 8% 6% 9% 11% 28%	5376
	11th to 20th	Night	1 5% 4 10% 6% 6% 7% 6% 8% 9% 38%	5136
	21st to end	Night	5% 12% 5% 11% 8% 7% 8% 6% 7% 7% 24%	5140
April	1st to 10th	Night	4 11% 4 11% 8% 7% 6% 5% 7% 7% 30%	2000
	11th to 20th	Night	3 11% 4 11% 8% 7% 7% 5% 5% 6% 32%	1970
	21st to end	Night	4 11% 3 9% 6% 5% 5% 6% 6% 8% 36%	1605
May	1st to 10th	Night	5% 11% 4 9% 6% 5% 5% 3 5% 6% 42%	3640
	11th to 20th	Night	4 9% 5% 11% 6% 5% 5% 5% 7% 10% 32%	3616
	21st to end	Night	7% 9% 3 8% 6% 5% 5% 4 7% 8% 38%	3972
June	1st to 10th	Night	12% 8% 3 8% 7% 5% 5% 5% 6% 9% 32%	1230
	11th to 20th	Night	10% 10% 3 8% 7% 6% 6% 5% 7% 8% 31%	1200
	21st to end	Night	7% 8% 3 7% 5% 4 4 4 6% 8% 44%	1200
July	1st to 10th	Night	8% 5% 3 5% 4 4 5% 3 6% 7% 50%	3126
	11th to 20th	Night	5% 3 2 4 3 3 4 3 6% 7% 62%	3244
	21st to end	Night	4 4 2 6% 4 3 5% 4 6% 8% 55%	3969
August	1st to 10th	Night	4 5% 2 6% 4 4 4 3 6% 8% 55%	2609
	11th to 20th	Night	5% 4 2 6% 5% 5% 6% 5% 9% 9% 45%	2642
	21st to end	Night	8% 6% 3 7% 4 5% 5% 4 5% 7% 46%	3471
September	1st to 10th	Night	6% 6% 1 6% 3 3 4 3 5% 8% 55%	2000
	11th to 20th	Night	8% 6% 2 7% 4 4 5% 5% 6% 7% 47%	2000
	21st to end	Night	9% 9% 4 7% 4 5% 4 3 6% 8% 41%	2255
October	1st to 10th	Night	8% 9% 3 8% 5% 5% 4 4 6% 7% 43%	3920
	11th to 20th	Night	12% 11% 3 8% 5% 5% 4 5% 6% 8% 34%	3950
	21st to end	Night	6% 11% 4 11% 6% 5% 5% 4 5% 6% 35%	4600
November	1st to 10th	Night	9% 14% 4 10% 7% 6% 6% 5% 6% 7% 25%	2828
	11th to 20th	Night	5% 13% 5% 11% 8% 6% 6% 5% 6% 7% 27%	2940
	21st to end	Night	6% 15% 5% 10% 8% 8% 6% 6% 6% 7% 23%	3014
December	1st to 10th	Night	4 9% 4 9% 6% 6% 5% 6% 7% 9% 34%	5040
	11th to 20th	Night	6% 15% 6% 14% 9% 7% 6% 5% 6% 6% 20%	5983
	21st to end	Night	3 12% 5% 12% 8% 7% 7% 5% 7% 8% 25%	7999

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	61% 8% 12% 15% 3	4125
	11th to 20th	Day	37% 8% 17% 26% 8% 3	4398
	21st to end	Day	49% 11% 15% 15% 10%	5187
February	1st to 10th	Day	58% 6% 11% 13% 9% 2	1748
	11th to 20th	Day	51% 7% 15% 18% 9% 1	1810
	21st to end	Day	58% 5% 14% 15% 8%	1580
March	1st to 10th	Day	45% 10% 14% 20% 11%	4518
	11th to 20th	Day	45% 6% 16% 25% 8%	4862
	21st to end	Day	56% 8% 14% 14% 8%	5834
April	1st to 10th	Day	59% 8% 12% 17% 5%	2400
	11th to 20th	Day	55% 7% 10% 16% 10% 2	2377
	21st to end	Day	53% 7% 14% 17% 8%	2795
May	1st to 10th	Day	40% 5% 9% 31% 14% 1	6320
	11th to 20th	Day	53% 9% 13% 20% 5%	6280
	21st to end	Day	51% 8% 16% 20% 4 1	6904
June	1st to 10th	Day	52% 7% 11% 16% 11% 4	3163
	11th to 20th	Day	59% 6% 10% 16% 8%	3200
	21st to end	Day	45% 6% 14% 21% 12% 2	3200
July	1st to 10th	Day	31% 6% 11% 21% 19% 11%	6755
	11th to 20th	Day	26% 8% 13% 24% 22% 7%	6635
	21st to end	Day	25% 8% 19% 27% 15% 5%	6681
August	1st to 10th	Day	24% 7% 12% 30% 25% 2	4524
	11th to 20th	Day	34% 11% 20% 24% 10% 2	4435
	21st to end	Day	35% 6% 19% 29% 9% 2	4443
September	1st to 10th	Day	34% 5% 14% 29% 14% 3	2400
	11th to 20th	Day	42% 4 12% 26% 13% 3	2400
	21st to end	Day	44% 8% 18% 19% 10% 2	2144
October	1st to 10th	Day	39% 5% 21% 26% 8% 1	3280
	11th to 20th	Day	48% 5% 13% 26% 7%	3205
	21st to end	Day	48% 9% 18% 21% 4	3200
November	1st to 10th	Day	58% 6% 12% 18% 6% 1	1688
	11th to 20th	Day	52% 8% 16% 18% 6% 1	1680
	21st to end	Day	55% 7% 15% 16% 6% 1	1582
December	1st to 10th	Day	47% 8% 24% 18% 3	2360
	11th to 20th	Day	58% 8% 17% 12% 5%	2426
	21st to end	Day	58% 9% 16% 16% 2	3243
January	1st to 10th	Night	60% 9% 13% 13% 6%	8770
	11th to 20th	Night	40% 7% 16% 25% 8% 4	8546
	21st to end	Night	46% 10% 15% 17% 11%	8994
February	1st to 10th	Night	57% 5% 13% 15% 8% 2	2868
	11th to 20th	Night	48% 6% 16% 19% 9% 2	2599
	21st to end	Night	54% 6% 14% 17% 8%	2049
March	1st to 10th	Night	39% 11% 15% 23% 11%	5376
	11th to 20th	Night	37% 6% 18% 25% 14%	5137
	21st to end	Night	54% 8% 12% 18% 9%	5140
April	1st to 10th	Night	48% 7% 18% 20% 7%	2000
	11th to 20th	Night	48% 8% 13% 20% 11%	1970
	21st to end	Night	43% 5% 15% 25% 11%	1605
May	1st to 10th	Night	42% 5% 8% 27% 17% 1	3637
	11th to 20th	Night	42% 9% 15% 28% 5%	3616
	21st to end	Night	40% 8% 17% 28% 6%	3972
June	1st to 10th	Night	45% 6% 13% 23% 10% 3	1230
	11th to 20th	Night	47% 6% 15% 21% 10%	1200
	21st to end	Night	36% 5% 18% 26% 13% 2	1200
July	1st to 10th	Night	30% 7% 14% 19% 22% 8%	3091
	11th to 20th	Night	20% 7% 15% 28% 26% 5%	3202
	21st to end	Night	23% 9% 17% 27% 15% 9%	3857
August	1st to 10th	Night	26% 6% 11% 25% 29% 3	2601
	11th to 20th	Night	30% 9% 17% 28% 13% 2	2666
	21st to end	Night	33% 7% 21% 26% 11% 2	3471
September	1st to 10th	Night	28% 5% 16% 32% 17% 3	2000
	11th to 20th	Night	34% 5% 16% 27% 14% 4	2000
	21st to end	Night	40% 6% 19% 21% 12% 3	2255
October	1st to 10th	Night	38% 6% 20% 28% 8%	3920
	11th to 20th	Night	46% 5% 13% 27% 9%	3950
	21st to end	Night	45% 6% 17% 26% 5%	4600
November	1st to 10th	Night	55% 7% 15% 15% 7%	2828
	11th to 20th	Night	54% 8% 14% 15% 8% 1	2940
	21st to end	Night	57% 6% 17% 13% 7% 1	3014
December	1st to 10th	Night	44% 9% 19% 23% 5%	5040
	11th to 20th	Night	63% 8% 13% 12% 4	5980
	21st to end	Night	53% 8% 15% 19% 5%	7999

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	16% 25% 26% 20% 8% 5%	220
	11th to 20th	Day	15% 18% 26% 23% 15% 3	220
	21st to end	Day	16% 20% 30% 20% 12% 2	242
February	1st to 10th	Day	17% 23% 33% 21% 6% 1	288
	11th to 20th	Day	14% 25% 30% 21% 9% 1	411
	21st to end	Day	17% 22% 31% 17% 11% 2	379
March	1st to 10th	Day	20% 25% 25% 19% 10% 1	500
	11th to 20th	Day	19% 24% 27% 18% 9% 3	500
	21st to end	Day	21% 25% 26% 17% 9% 3	550
April	1st to 10th	Day	24% 20% 27% 21% 6% 2	500
	11th to 20th	Day	21% 24% 24% 19% 10% 3	492
	21st to end	Day	21% 17% 30% 20% 8% 4	500
May	1st to 10th	Day	21% 17% 25% 25% 8% 3	503
	11th to 20th	Day	19% 13% 19% 28% 16% 5%	528
	21st to end	Day	21% 12% 26% 25% 13% 4	573
June	1st to 10th	Day	23% 18% 26% 22% 10% 2	893
	11th to 20th	Day	23% 12% 26% 25% 12% 2	930
	21st to end	Day	15% 12% 27% 25% 17% 4	930
July	1st to 10th	Day	13% 14% 26% 29% 14% 3	744
	11th to 20th	Day	11% 13% 27% 29% 15% 5%	693
	21st to end	Day	7% 8% 21% 37% 20% 6%	575
August	1st to 10th	Day	7% 6% 24% 30% 26% 7%	527
	11th to 20th	Day	8% 11% 26% 28% 19% 7%	517
	21st to end	Day	13% 12% 25% 30% 14% 6%	583
September	1st to 10th	Day	14% 12% 24% 27% 18% 5%	530
	11th to 20th	Day	20% 14% 24% 23% 15% 5%	530
	21st to end	Day	24% 16% 27% 21% 10% 2	530
October	1st to 10th	Day	22% 16% 25% 19% 14% 3	530
	11th to 20th	Day	23% 20% 22% 18% 14% 2	499
	21st to end	Day	24% 20% 24% 20% 11% 1	363
November	1st to 10th	Day	29% 20% 25% 17% 9% 1	242
	11th to 20th	Day	25% 22% 26% 13% 11% 4	220
	21st to end	Day	21% 18% 29% 18% 9% 5%	220
December	1st to 10th	Day	18% 14% 25% 19% 18% 6%	220
	11th to 20th	Day	19% 25% 28% 15% 9% 5%	220
	21st to end	Day	16% 15% 32% 24% 10% 3	242
January	1st to 10th	Night	20% 20% 23% 25% 10% 1	950
	11th to 20th	Night	15% 14% 26% 31% 13% 1	900
	21st to end	Night	10% 18% 26% 30% 14% 2	924
February	1st to 10th	Night	16% 18% 23% 29% 11% 3	840
	11th to 20th	Night	12% 17% 25% 31% 14% 1	804
	21st to end	Night	13% 18% 27% 24% 17% 2	660
March	1st to 10th	Night	13% 22% 22% 26% 15% 3	800
	11th to 20th	Night	11% 25% 28% 21% 14% 2	800
	21st to end	Night	14% 19% 27% 23% 12% 4	880
April	1st to 10th	Night	13% 18% 25% 26% 15% 3	800
	11th to 20th	Night	12% 20% 26% 25% 15% 1	782
	21st to end	Night	9% 20% 31% 25% 11% 3	405
May	1st to 10th	Night	13% 14% 26% 30% 15% 3	400
	11th to 20th	Night	10% 12% 25% 36% 14% 3	394
	21st to end	Night	16% 7% 28% 27% 20% 2	433
June	1st to 10th	Night	16% 13% 31% 28% 10% 2	400
	11th to 20th	Night	13% 14% 32% 27% 12% 4	400
	21st to end	Night	9% 12% 29% 28% 19% 3	400
July	1st to 10th	Night	9% 7% 28% 35% 18% 2	390
	11th to 20th	Night	7% 9% 30% 32% 20% 1	388
	21st to end	Night	7% 4 27% 33% 26% 4	438
August	1st to 10th	Night	7% 6% 19% 34% 29% 5%	398
	11th to 20th	Night	8% 5% 25% 27% 30% 5%	435
	21st to end	Night	10% 9% 23% 30% 24% 4	795
September	1st to 10th	Night	10% 8% 22% 28% 27% 5%	800
	11th to 20th	Night	12% 9% 20% 24% 27% 8%	800
	21st to end	Night	18% 17% 23% 23% 16% 4	800
October	1st to 10th	Night	13% 14% 24% 28% 18% 3	800
	11th to 20th	Night	16% 19% 22% 24% 16% 3	800
	21st to end	Night	18% 19% 27% 23% 12% 2	880
November	1st to 10th	Night	21% 18% 27% 25% 8% 1	820
	11th to 20th	Night	18% 24% 23% 22% 12% 1	840
	21st to end	Night	17% 18% 25% 25% 12% 3	914
December	1st to 10th	Night	14% 15% 24% 30% 14% 3	1050
	11th to 20th	Night	17% 21% 26% 25% 10% 1	1124
	21st to end	Night	16% 19% 26% 28% 10% 2	1213

Page generated at 2026-02-12 22:42:11. Version ac07

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