Kalaloch Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kalaloch Beach clear sky chart from 2005-11-06 to 2026-03-03.

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	23% 11% 3 8% 5% 5% 5% 4 6% 7% 24%	134837
	Night	28% 13% 4 8% 4 4 4 3 4 6% 23%	135036
Transparency	Day	59% 2 12% 17% 9% 1	134545
	Night	63% 2 10% 15% 8% 2	134906
Seeing	Day	33% 9% 22% 22% 11% 4	17138
	Night	38% 4 12% 25% 18% 4	25485

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	41% 18% 3 10% 4 3 3 2 3 2 9%	4125
	11th to 20th	Day	23% 9% 3 7% 3 3 4 3 4 6% 34%	4119
	21st to end	Day	38% 11% 3 7% 4 3 3 2 3 4 20%	5620
February	1st to 10th	Day	35% 13% 4 8% 4 4 4 3 6% 5% 14%	1890
	11th to 20th	Day	34% 12% 3 9% 5% 3 3 2 4 5% 21%	1845
	21st to end	Day	32% 17% 3 9% 5% 5% 4 3 4 4 15%	1557
March	1st to 10th	Day	27% 17% 4 9% 5% 4 5% 4 5% 5% 16%	4841
	11th to 20th	Day	28% 12% 4 8% 5% 4 4 3 5% 6% 20%	5000
	21st to end	Day	31% 14% 4 9% 5% 5% 4 4 4 5% 14%	5486
April	1st to 10th	Day	30% 13% 3 10% 6% 5% 5% 4 5% 5% 14%	2398
	11th to 20th	Day	25% 11% 3 8% 5% 4 5% 4 4 6% 25%	2513
	21st to end	Day	26% 12% 3 9% 5% 4 4 4 5% 6% 21%	2600
May	1st to 10th	Day	19% 8% 3 7% 4 5% 4 3 5% 7% 34%	6201
	11th to 20th	Day	19% 10% 4 10% 5% 5% 5% 4 7% 9% 21%	6277
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 4 6% 9% 25%	6993
June	1st to 10th	Day	23% 11% 3 8% 6% 5% 5% 4 6% 8% 23%	3000
	11th to 20th	Day	22% 12% 3 9% 6% 4 5% 5% 6% 7% 21%	3000
	21st to end	Day	19% 10% 3 8% 6% 6% 5% 4 6% 7% 25%	3000
July	1st to 10th	Day	9% 6% 2 7% 6% 5% 6% 5% 9% 11% 36%	6780
	11th to 20th	Day	6% 9% 2 7% 6% 5% 6% 5% 7% 8% 38%	6780
	21st to end	Day	10% 12% 4 10% 6% 6% 6% 4 6% 9% 27%	6975
August	1st to 10th	Day	8% 12% 4 10% 9% 8% 6% 5% 8% 8% 20%	4258
	11th to 20th	Day	14% 9% 4 9% 6% 6% 5% 5% 8% 9% 24%	4156
	21st to end	Day	19% 8% 3 7% 5% 5% 4 4 6% 9% 31%	4608
September	1st to 10th	Day	13% 8% 4 7% 6% 5% 5% 4 6% 8% 33%	2400
	11th to 20th	Day	16% 10% 4 9% 6% 6% 4 3 6% 8% 28%	2311
	21st to end	Day	22% 7% 3 7% 6% 5% 5% 3 5% 7% 30%	2160
October	1st to 10th	Day	17% 8% 2 7% 5% 5% 6% 4 7% 9% 29%	3280
	11th to 20th	Day	33% 9% 3 7% 4 4 4 3 4 5% 22%	3261
	21st to end	Day	25% 9% 4 8% 5% 5% 6% 4 5% 6% 23%	3398
November	1st to 10th	Day	38% 11% 3 8% 4 4 4 4 4 4 15%	1648
	11th to 20th	Day	39% 11% 4 7% 5% 4 3 2 4 4 18%	1680
	21st to end	Day	38% 11% 3 8% 5% 4 3 3 4 5% 18%	1680
December	1st to 10th	Day	26% 10% 4 8% 5% 4 4 2 4 5% 29%	2700
	11th to 20th	Day	43% 11% 3 9% 5% 4 4 3 4 4 9%	2722
	21st to end	Day	40% 16% 4 9% 4 4 3 3 3 4 10%	3575
January	1st to 10th	Night	38% 18% 4 10% 5% 4 3 2 3 3 9%	8770
	11th to 20th	Night	26% 12% 3 6% 3 3 3 3 5% 8% 28%	8779
	21st to end	Night	36% 11% 3 7% 3 3 3 2 4 6% 20%	8555
February	1st to 10th	Night	34% 15% 3 8% 4 4 4 3 4 5% 16%	2730
	11th to 20th	Night	32% 14% 4 7% 4 4 3 2 3 5% 22%	2662
	21st to end	Night	34% 17% 4 8% 5% 4 3 2 4 4 16%	2249
March	1st to 10th	Night	26% 16% 4 10% 6% 5% 4 3 4 5% 16%	5093
	11th to 20th	Night	28% 16% 3 8% 4 3 4 3 5% 4 21%	4999
	21st to end	Night	38% 18% 4 8% 4 4 3 2 3 3 12%	5489
April	1st to 10th	Night	30% 15% 5% 9% 6% 5% 4 4 4 4 16%	2001
	11th to 20th	Night	25% 14% 4 9% 5% 4 3 3 4 6% 22%	1835
	21st to end	Night	27% 13% 3 10% 6% 6% 4 3 4 5% 20%	1800
May	1st to 10th	Night	19% 10% 3 7% 3 3 3 2 4 7% 38%	3762
	11th to 20th	Night	21% 17% 5% 11% 5% 5% 4 4 5% 4 19%	3616
	21st to end	Night	25% 13% 4 8% 5% 4 5% 3 5% 6% 23%	3866
June	1st to 10th	Night	23% 13% 3 8% 5% 3 5% 4 4 5% 27%	1400
	11th to 20th	Night	21% 12% 3 10% 5% 6% 4 5% 5% 6% 22%	1400
	21st to end	Night	16% 15% 4 8% 4 3 4 3 5% 7% 30%	1400
July	1st to 10th	Night	10% 11% 3 6% 4 3 2 3 4 5% 49%	3180
	11th to 20th	Night	7% 12% 2 6% 5% 4 4 2 4 6% 48%	3180
	21st to end	Night	10% 19% 5% 9% 4 3 4 3 5% 7% 33%	3865
August	1st to 10th	Night	8% 18% 5% 10% 6% 4 4 4 5% 7% 30%	2898
	11th to 20th	Night	15% 14% 3 7% 4 4 5% 3 5% 7% 33%	2902
	21st to end	Night	20% 9% 3 7% 4 4 3 3 5% 7% 37%	3301
September	1st to 10th	Night	11% 10% 3 7% 4 3 3 3 5% 8% 42%	2000
	11th to 20th	Night	19% 10% 4 8% 5% 4 4 3 3 4 35%	2085
	21st to end	Night	22% 8% 3 7% 4 3 4 3 4 6% 36%	2240
October	1st to 10th	Night	18% 7% 3 6% 4 4 5% 4 7% 9% 34%	3920
	11th to 20th	Night	32% 9% 3 7% 4 4 3 3 4 7% 24%	3897
	21st to end	Night	30% 9% 3 8% 5% 5% 4 4 4 5% 21%	4389
November	1st to 10th	Night	39% 11% 3 7% 5% 4 4 2 4 4 16%	2870
	11th to 20th	Night	39% 13% 3 8% 4 3 3 2 4 4 17%	2940
	21st to end	Night	35% 11% 4 8% 5% 4 4 3 4 5% 18%	2940
December	1st to 10th	Night	27% 11% 3 7% 5% 5% 4 4 6% 8% 22%	4700
	11th to 20th	Night	44% 14% 4 9% 5% 4 3 2 3 3 9%	5700
	21st to end	Night	40% 15% 4 10% 5% 4 3 3 4 4 8%	7623

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	85% 1 4 7% 2 1	4125
	11th to 20th	Day	54% 1 10% 18% 13% 4	4140
	21st to end	Day	70% 1 5% 16% 8% 1	5621
February	1st to 10th	Day	74% 3 7% 10% 5% 1	1890
	11th to 20th	Day	72% 2 5% 13% 6% 2	1854
	21st to end	Day	76% 2 7% 9% 6%	1557
March	1st to 10th	Day	76% 1 7% 12% 4	4841
	11th to 20th	Day	70% 1 7% 15% 6% 1	5000
	21st to end	Day	79% 1 10% 9% 1	5486
April	1st to 10th	Day	75% 3 10% 9% 2	2398
	11th to 20th	Day	68% 2 8% 14% 7% 1	2513
	21st to end	Day	69% 2 11% 14% 3	2600
May	1st to 10th	Day	54% 2 15% 21% 9%	6201
	11th to 20th	Day	63% 2 17% 15% 3	6280
	21st to end	Day	61% 3 20% 12% 4	6994
June	1st to 10th	Day	60% 4 17% 13% 6% 1	3000
	11th to 20th	Day	65% 4 14% 13% 4	3000
	21st to end	Day	55% 3 18% 16% 6% 1	3000
July	1st to 10th	Day	29% 3 20% 19% 20% 9%	6706
	11th to 20th	Day	28% 1 16% 27% 26% 1	6699
	21st to end	Day	40% 2 19% 28% 10% 1	6779
August	1st to 10th	Day	36% 2 11% 31% 18% 2	4241
	11th to 20th	Day	52% 3 18% 18% 7% 2	4195
	21st to end	Day	47% 2 13% 26% 11% 1	4607
September	1st to 10th	Day	42% 3 14% 23% 13% 5%	2400
	11th to 20th	Day	51% 3 12% 18% 14% 2	2311
	21st to end	Day	49% 3 14% 21% 10% 3	2160
October	1st to 10th	Day	53% 2 13% 26% 6% 1	3280
	11th to 20th	Day	65% 3 9% 16% 6%	3261
	21st to end	Day	65% 2 11% 11% 10% 2	3398
November	1st to 10th	Day	77% 2 9% 9% 2 1	1648
	11th to 20th	Day	73% 2 6% 11% 6% 3	1680
	21st to end	Day	70% 3 6% 12% 8% 2	1680
December	1st to 10th	Day	61% 1 5% 16% 13% 3	2700
	11th to 20th	Day	82% 1 6% 7% 3	2725
	21st to end	Day	83% 1 6% 7% 2 1	3575
January	1st to 10th	Night	84% 1 4 7% 4 1	8770
	11th to 20th	Night	55% 1 9% 17% 13% 5%	8820
	21st to end	Night	67% 1 5% 15% 12% 1	8555
February	1st to 10th	Night	72% 3 7% 11% 6% 1	2730
	11th to 20th	Night	68% 2 7% 12% 9% 2	2664
	21st to end	Night	74% 2 7% 11% 5% 1	2249
March	1st to 10th	Night	71% 1 6% 15% 5%	5093
	11th to 20th	Night	69% 2 8% 14% 7% 1	5000
	21st to end	Night	80% 1 10% 8% 2	5489
April	1st to 10th	Night	74% 3 11% 10% 3	2001
	11th to 20th	Night	65% 1 10% 13% 9% 1	1835
	21st to end	Night	66% 2 10% 14% 7%	1800
May	1st to 10th	Night	49% 2 14% 27% 8%	3759
	11th to 20th	Night	64% 2 13% 14% 6%	3616
	21st to end	Night	63% 4 18% 13% 1	3866
June	1st to 10th	Night	57% 3 14% 18% 6% 1	1400
	11th to 20th	Night	55% 4 19% 18% 4	1400
	21st to end	Night	49% 4 19% 19% 6% 2	1400
July	1st to 10th	Night	29% 2 19% 23% 14% 13%	3145
	11th to 20th	Night	30% 2 14% 24% 28% 2	3138
	21st to end	Night	38% 2 16% 31% 11% 2	3756
August	1st to 10th	Night	41% 3 13% 26% 15% 2	2890
	11th to 20th	Night	48% 2 20% 20% 8% 3	2929
	21st to end	Night	46% 3 10% 29% 11% 1	3301
September	1st to 10th	Night	37% 4 15% 25% 15% 4	2000
	11th to 20th	Night	51% 3 12% 19% 12% 3	2085
	21st to end	Night	50% 2 11% 21% 13% 3	2240
October	1st to 10th	Night	46% 1 15% 29% 7% 1	3920
	11th to 20th	Night	64% 1 11% 16% 8%	3897
	21st to end	Night	67% 2 8% 12% 9% 2	4389
November	1st to 10th	Night	74% 2 7% 13% 3 1	2870
	11th to 20th	Night	74% 2 8% 8% 5% 3	2940
	21st to end	Night	71% 1 8% 10% 8% 2	2940
December	1st to 10th	Night	61% 2 7% 16% 14% 1	4700
	11th to 20th	Night	83% 1 6% 7% 3	5696
	21st to end	Night	85% 1 5% 6% 2	7623

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	51% 8% 17% 14% 7% 3	220
	11th to 20th	Day	45% 6% 12% 17% 13% 7%	220
	21st to end	Day	44% 7% 14% 19% 12% 4	410
February	1st to 10th	Day	47% 10% 19% 15% 7% 1	430
	11th to 20th	Day	46% 11% 19% 14% 8% 1	425
	21st to end	Day	47% 12% 21% 14% 5% 1	355
March	1st to 10th	Day	45% 9% 21% 17% 7% 1	498
	11th to 20th	Day	44% 9% 17% 17% 10% 2	500
	21st to end	Day	47% 12% 17% 16% 7% 1	550
April	1st to 10th	Day	41% 11% 23% 16% 7% 2	500
	11th to 20th	Day	36% 12% 23% 17% 8% 3	492
	21st to end	Day	36% 13% 23% 17% 7% 3	500
May	1st to 10th	Day	30% 14% 23% 21% 10% 3	503
	11th to 20th	Day	37% 10% 24% 18% 9% 3	528
	21st to end	Day	31% 10% 27% 21% 8% 3	611
June	1st to 10th	Day	32% 10% 24% 23% 8% 3	730
	11th to 20th	Day	28% 15% 30% 20% 5% 2	730
	21st to end	Day	23% 8% 26% 26% 13% 4	730
July	1st to 10th	Day	21% 6% 28% 32% 11% 3	721
	11th to 20th	Day	14% 7% 31% 34% 11% 4	718
	21st to end	Day	12% 5% 28% 32% 17% 7%	624
August	1st to 10th	Day	17% 6% 20% 31% 20% 6%	527
	11th to 20th	Day	15% 5% 21% 31% 20% 8%	517
	21st to end	Day	21% 9% 22% 28% 12% 8%	583
September	1st to 10th	Day	20% 6% 25% 26% 16% 7%	530
	11th to 20th	Day	24% 8% 21% 28% 15% 4	530
	21st to end	Day	28% 9% 22% 21% 13% 6%	530
October	1st to 10th	Day	27% 8% 24% 22% 14% 6%	530
	11th to 20th	Day	40% 7% 19% 16% 14% 5%	530
	21st to end	Day	42% 11% 19% 16% 9% 4	524
November	1st to 10th	Day	47% 13% 15% 14% 9% 2	220
	11th to 20th	Day	46% 6% 15% 13% 11% 9%	220
	21st to end	Day	45% 7% 15% 15% 10% 9%	220
December	1st to 10th	Day	49% 5% 10% 11% 14% 10%	220
	11th to 20th	Day	56% 7% 10% 15% 10% 1	220
	21st to end	Day	50% 6% 15% 18% 8% 4	242
January	1st to 10th	Night	57% 6% 11% 14% 10% 2	950
	11th to 20th	Night	46% 5% 10% 21% 15% 2	950
	21st to end	Night	45% 5% 11% 21% 13% 4	930
February	1st to 10th	Night	45% 5% 13% 25% 11% 1	840
	11th to 20th	Night	43% 5% 14% 24% 13% 1	824
	21st to end	Night	47% 5% 13% 23% 10% 1	692
March	1st to 10th	Night	41% 7% 15% 21% 13% 2	808
	11th to 20th	Night	47% 5% 13% 23% 11% 3	800
	21st to end	Night	49% 5% 11% 23% 11% 1	880
April	1st to 10th	Night	42% 5% 12% 26% 12% 3	800
	11th to 20th	Night	35% 7% 14% 29% 13% 2	647
	21st to end	Night	36% 5% 12% 28% 17% 3	600
May	1st to 10th	Night	28% 3 13% 30% 21% 3	457
	11th to 20th	Night	32% 4 11% 26% 22% 5%	394
	21st to end	Night	34% 3 9% 28% 21% 4	433
June	1st to 10th	Night	29% 4 12% 26% 26% 4	400
	11th to 20th	Night	25% 5% 10% 39% 17% 4	400
	21st to end	Night	22% 3 10% 29% 30% 6%	400
July	1st to 10th	Night	15% 3 10% 35% 34% 3	390
	11th to 20th	Night	13% 3 13% 34% 31% 6%	388
	21st to end	Night	9% 3 12% 30% 38% 8%	438
August	1st to 10th	Night	17% 2 6% 23% 38% 14%	570
	11th to 20th	Night	13% 2 5% 26% 39% 16%	594
	21st to end	Night	20% 3 9% 26% 34% 7%	690
September	1st to 10th	Night	15% 3 8% 34% 31% 9%	800
	11th to 20th	Night	25% 2 8% 25% 28% 12%	800
	21st to end	Night	28% 4 13% 27% 23% 6%	800
October	1st to 10th	Night	27% 2 11% 28% 27% 6%	800
	11th to 20th	Night	36% 4 12% 25% 16% 7%	800
	21st to end	Night	40% 5% 13% 25% 14% 3	880
November	1st to 10th	Night	50% 4 13% 24% 9%	820
	11th to 20th	Night	51% 4 13% 19% 10% 3	840
	21st to end	Night	46% 5% 13% 21% 11% 4	840
December	1st to 10th	Night	40% 4 9% 28% 16% 3	840
	11th to 20th	Night	52% 7% 14% 18% 8% 2	945
	21st to end	Night	54% 6% 13% 19% 7% 1	1045

Page generated at 2026-02-27 22:40:20. Version ac07

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