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 2024-12-02.

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% 4 4 5% 7% 24%	105724
	Night	28% 13% 4 8% 4 4 4 3 4 5% 23%	102504
Transparency	Day	59% 2 11% 17% 9% 2	105473
	Night	63% 2 10% 16% 8% 2	102401
Seeing	Day	32% 9% 22% 22% 11% 4	15611
	Night	37% 5% 11% 25% 18% 4	23812

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% 20% 3 8% 5% 3 3 2 3 3 10%	2219
	11th to 20th	Day	34% 12% 3 9% 4 4 4 2 3 5% 20%	2199
	21st to end	Day	49% 14% 3 6% 4 3 3 2 3 3 9%	3022
February	1st to 10th	Day	37% 13% 4 7% 4 4 4 2 6% 5% 14%	1710
	11th to 20th	Day	34% 12% 3 9% 5% 3 3 2 4 5% 20%	1665
	21st to end	Day	30% 17% 3 9% 5% 4 4 3 4 4 15%	1413
March	1st to 10th	Day	24% 18% 3 8% 5% 4 5% 4 6% 6% 17%	3351
	11th to 20th	Day	24% 10% 4 8% 5% 4 4 3 5% 6% 27%	3490
	21st to end	Day	28% 15% 4 8% 5% 4 4 3 4 5% 18%	3825
April	1st to 10th	Day	30% 13% 4 10% 6% 5% 5% 4 5% 5% 14%	2278
	11th to 20th	Day	26% 12% 4 8% 5% 4 5% 4 4 5% 24%	2386
	21st to end	Day	27% 12% 4 9% 5% 4 4 4 4 6% 20%	2470
May	1st to 10th	Day	22% 10% 3 6% 4 5% 4 3 4 6% 34%	4340
	11th to 20th	Day	15% 9% 4 9% 5% 5% 5% 4 7% 9% 27%	4377
	21st to end	Day	27% 10% 3 8% 5% 5% 5% 4 6% 8% 20%	4875
June	1st to 10th	Day	24% 11% 3 8% 6% 4 4 4 6% 8% 22%	2850
	11th to 20th	Day	23% 12% 3 9% 5% 4 4 5% 6% 7% 21%	2850
	21st to end	Day	18% 10% 3 8% 6% 5% 5% 4 7% 7% 25%	2850
July	1st to 10th	Day	9% 7% 2 6% 4 4 5% 5% 8% 11% 39%	4740
	11th to 20th	Day	8% 9% 3 7% 7% 6% 6% 4 6% 8% 37%	4740
	21st to end	Day	14% 12% 3 8% 6% 5% 4 4 6% 9% 30%	4863
August	1st to 10th	Day	7% 12% 4 10% 9% 8% 6% 6% 8% 8% 20%	4127
	11th to 20th	Day	14% 9% 4 9% 7% 6% 5% 5% 8% 9% 24%	4026
	21st to end	Day	19% 8% 3 7% 5% 5% 4 4 6% 10% 31%	4467
September	1st to 10th	Day	14% 8% 4 6% 6% 5% 5% 4 6% 8% 35%	2280
	11th to 20th	Day	16% 10% 4 9% 6% 6% 4 3 6% 8% 28%	2196
	21st to end	Day	22% 7% 3 7% 6% 5% 4 3 5% 7% 30%	2052
October	1st to 10th	Day	18% 8% 3 7% 5% 5% 6% 4 7% 9% 29%	3180
	11th to 20th	Day	34% 9% 3 7% 4 4 4 3 4 6% 22%	3161
	21st to end	Day	24% 9% 4 8% 5% 6% 6% 4 5% 6% 23%	3292
November	1st to 10th	Day	38% 12% 3 8% 4 4 3 4 4 4 15%	1568
	11th to 20th	Day	38% 12% 4 7% 5% 4 3 2 4 4 19%	1600
	21st to end	Day	38% 11% 3 8% 5% 3 3 3 4 5% 18%	1600
December	1st to 10th	Day	30% 13% 4 8% 5% 4 4 2 4 5% 22%	1528
	11th to 20th	Day	38% 12% 3 8% 6% 4 4 4 4 4 13%	1692
	21st to end	Day	37% 17% 4 8% 4 4 3 2 3 4 13%	2442
January	1st to 10th	Night	38% 20% 4 9% 5% 4 3 2 3 3 10%	4726
	11th to 20th	Night	35% 13% 3 7% 4 3 3 3 4 5% 19%	4699
	21st to end	Night	50% 13% 4 7% 4 2 3 2 2 4 10%	4640
February	1st to 10th	Night	35% 15% 3 7% 4 4 4 3 4 6% 16%	2470
	11th to 20th	Night	33% 14% 4 7% 4 3 3 2 3 5% 21%	2402
	21st to end	Night	34% 16% 4 8% 5% 4 3 3 4 4 16%	2041
March	1st to 10th	Night	27% 18% 4 8% 5% 5% 4 3 4 5% 17%	3519
	11th to 20th	Night	24% 14% 3 7% 4 3 4 3 5% 5% 29%	3489
	21st to end	Night	32% 22% 5% 8% 4 4 3 2 3 3 16%	3828
April	1st to 10th	Night	30% 16% 5% 9% 6% 5% 3 4 3 4 16%	1901
	11th to 20th	Night	25% 15% 4 9% 5% 4 3 3 4 6% 21%	1743
	21st to end	Night	28% 12% 3 10% 6% 6% 4 3 3 5% 20%	1710
May	1st to 10th	Night	23% 10% 3 7% 3 3 3 3 4 6% 36%	2620
	11th to 20th	Night	15% 15% 4 9% 5% 5% 4 4 6% 5% 27%	2516
	21st to end	Night	29% 16% 4 7% 4 3 3 2 4 4 23%	2684
June	1st to 10th	Night	24% 13% 3 9% 5% 3 5% 4 4 5% 25%	1330
	11th to 20th	Night	22% 12% 3 10% 5% 5% 4 5% 5% 6% 22%	1330
	21st to end	Night	17% 15% 4 8% 4 3 4 3 5% 7% 30%	1330
July	1st to 10th	Night	9% 13% 3 6% 3 3 2 3 3 4 50%	2220
	11th to 20th	Night	9% 12% 2 6% 4 4 3 2 4 7% 47%	2220
	21st to end	Night	13% 15% 4 8% 3 3 3 3 5% 7% 35%	2686
August	1st to 10th	Night	7% 18% 5% 10% 6% 4 4 3 5% 7% 31%	2809
	11th to 20th	Night	15% 14% 3 7% 4 4 5% 3 5% 7% 33%	2812
	21st to end	Night	20% 9% 3 7% 3 4 3 2 5% 6% 37%	3200
September	1st to 10th	Night	12% 9% 3 7% 4 3 3 3 5% 8% 44%	1900
	11th to 20th	Night	20% 10% 4 8% 5% 4 4 3 3 4 34%	1981
	21st to end	Night	21% 8% 3 7% 4 3 4 3 4 6% 36%	2128
October	1st to 10th	Night	18% 7% 3 6% 4 4 5% 4 7% 10% 34%	3800
	11th to 20th	Night	33% 9% 3 7% 4 4 3 3 4 6% 23%	3777
	21st to end	Night	30% 9% 3 8% 5% 5% 4 4 4 5% 21%	4253
November	1st to 10th	Night	39% 12% 3 7% 4 4 4 2 4 4 16%	2730
	11th to 20th	Night	38% 13% 4 8% 4 3 3 2 4 4 17%	2800
	21st to end	Night	35% 12% 4 8% 5% 4 4 3 4 4 18%	2800
December	1st to 10th	Night	30% 13% 3 7% 5% 4 4 3 4 5% 22%	2686
	11th to 20th	Night	37% 13% 4 8% 5% 4 4 3 4 4 14%	3510
	21st to end	Night	39% 15% 4 10% 5% 4 3 3 3 3 11%	5214

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	82% 1 5% 8% 3 1	2219
	11th to 20th	Day	71% 2 9% 10% 5% 2	2220
	21st to end	Day	84% 1 4 7% 3 1	3022
February	1st to 10th	Day	74% 3 7% 10% 5% 1	1710
	11th to 20th	Day	73% 2 5% 12% 6% 3	1674
	21st to end	Day	75% 2 7% 10% 6%	1413
March	1st to 10th	Day	74% 1 8% 13% 4	3351
	11th to 20th	Day	60% 1 9% 19% 9% 1	3490
	21st to end	Day	75% 1 11% 11% 1	3825
April	1st to 10th	Day	75% 3 10% 9% 2	2278
	11th to 20th	Day	69% 2 8% 13% 7% 1	2386
	21st to end	Day	70% 3 10% 14% 3	2470
May	1st to 10th	Day	56% 2 13% 20% 8%	4340
	11th to 20th	Day	54% 3 20% 19% 4	4380
	21st to end	Day	68% 4 14% 10% 4	4876
June	1st to 10th	Day	62% 5% 17% 11% 5% 1	2850
	11th to 20th	Day	65% 4 14% 13% 4	2850
	21st to end	Day	55% 3 18% 16% 6% 1	2850
July	1st to 10th	Day	30% 3 8% 21% 25% 13%	4666
	11th to 20th	Day	31% 2 11% 28% 27% 1	4659
	21st to end	Day	41% 2 15% 27% 13% 2	4709
August	1st to 10th	Day	35% 2 10% 32% 18% 2	4110
	11th to 20th	Day	52% 3 18% 18% 7% 2	4065
	21st to end	Day	47% 2 13% 26% 11%	4466
September	1st to 10th	Day	40% 3 14% 23% 14% 5%	2280
	11th to 20th	Day	52% 4 12% 18% 13% 2	2196
	21st to end	Day	49% 3 13% 21% 10% 3	2052
October	1st to 10th	Day	53% 2 13% 26% 6% 1	3180
	11th to 20th	Day	66% 3 9% 15% 6%	3161
	21st to end	Day	65% 2 11% 11% 10% 2	3292
November	1st to 10th	Day	77% 2 9% 9% 2 1	1568
	11th to 20th	Day	72% 2 6% 11% 6% 3	1600
	21st to end	Day	70% 3 6% 12% 8% 2	1600
December	1st to 10th	Day	67% 2 7% 11% 10% 2	1528
	11th to 20th	Day	76% 2 6% 10% 5% 1	1695
	21st to end	Day	78% 2 7% 9% 3 1	2442
January	1st to 10th	Night	83% 1 4 7% 4 1	4726
	11th to 20th	Night	68% 1 9% 14% 5% 2	4740
	21st to end	Night	83% 2 4 7% 4 1	4640
February	1st to 10th	Night	72% 3 7% 11% 5% 1	2470
	11th to 20th	Night	69% 2 7% 12% 8% 2	2404
	21st to end	Night	74% 2 7% 12% 5% 1	2041
March	1st to 10th	Night	71% 1 7% 16% 4	3519
	11th to 20th	Night	60% 2 12% 17% 9% 1	3490
	21st to end	Night	76% 1 10% 9% 3	3828
April	1st to 10th	Night	74% 3 10% 10% 3	1901
	11th to 20th	Night	66% 2 9% 13% 8% 1	1743
	21st to end	Night	68% 3 10% 13% 7%	1710
May	1st to 10th	Night	51% 2 12% 27% 7%	2620
	11th to 20th	Night	53% 3 17% 18% 9%	2516
	21st to end	Night	66% 4 15% 13% 2	2684
June	1st to 10th	Night	58% 3 13% 18% 5% 1	1330
	11th to 20th	Night	55% 4 20% 17% 4	1330
	21st to end	Night	49% 4 19% 19% 6% 2	1330
July	1st to 10th	Night	32% 2 9% 22% 17% 19%	2185
	11th to 20th	Night	33% 2 11% 24% 29% 1	2178
	21st to end	Night	36% 3 12% 32% 14% 3	2601
August	1st to 10th	Night	41% 3 12% 26% 16% 2	2801
	11th to 20th	Night	47% 2 21% 20% 7% 2	2839
	21st to end	Night	46% 3 10% 29% 11% 1	3200
September	1st to 10th	Night	35% 4 15% 26% 16% 5%	1900
	11th to 20th	Night	51% 3 12% 18% 12% 4	1981
	21st to end	Night	50% 2 11% 21% 13% 3	2128
October	1st to 10th	Night	46% 1 15% 30% 7% 1	3800
	11th to 20th	Night	65% 1 11% 15% 8%	3777
	21st to end	Night	67% 2 9% 11% 9% 2	4253
November	1st to 10th	Night	74% 2 7% 13% 4 1	2730
	11th to 20th	Night	73% 2 9% 8% 6% 3	2800
	21st to end	Night	71% 1 8% 10% 9% 2	2800
December	1st to 10th	Night	66% 3 10% 12% 9% 2	2686
	11th to 20th	Night	75% 2 7% 9% 5% 1	3506
	21st to end	Night	82% 2 6% 7% 3	5214

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	48% 8% 20% 12% 9% 3	180
	11th to 20th	Day	52% 7% 13% 13% 11% 4	180
	21st to end	Day	47% 7% 14% 17% 12% 3	350
February	1st to 10th	Day	49% 9% 18% 15% 7% 1	370
	11th to 20th	Day	48% 12% 19% 13% 8% 1	365
	21st to end	Day	43% 13% 23% 16% 6% 1	307
March	1st to 10th	Day	45% 9% 22% 16% 7% 1	451
	11th to 20th	Day	42% 9% 17% 18% 11% 3	460
	21st to end	Day	46% 12% 17% 16% 7% 1	506
April	1st to 10th	Day	41% 11% 23% 15% 7% 2	460
	11th to 20th	Day	39% 12% 22% 16% 7% 3	452
	21st to end	Day	38% 13% 23% 16% 7% 3	460
May	1st to 10th	Day	30% 13% 22% 21% 10% 3	463
	11th to 20th	Day	36% 9% 23% 19% 9% 3	488
	21st to end	Day	32% 9% 26% 22% 8% 3	565
June	1st to 10th	Day	33% 9% 23% 24% 8% 3	680
	11th to 20th	Day	29% 15% 29% 20% 5% 2	680
	21st to end	Day	23% 9% 27% 25% 13% 3	680
July	1st to 10th	Day	21% 6% 27% 32% 11% 3	671
	11th to 20th	Day	15% 7% 30% 34% 10% 4	668
	21st to end	Day	11% 6% 28% 31% 17% 6%	578
August	1st to 10th	Day	16% 7% 20% 32% 20% 6%	487
	11th to 20th	Day	13% 5% 22% 31% 21% 8%	477
	21st to end	Day	21% 10% 23% 27% 12% 7%	539
September	1st to 10th	Day	20% 7% 25% 26% 16% 7%	490
	11th to 20th	Day	24% 8% 20% 29% 15% 4	490
	21st to end	Day	28% 9% 22% 21% 13% 7%	490
October	1st to 10th	Day	27% 8% 23% 22% 14% 6%	490
	11th to 20th	Day	41% 6% 18% 16% 14% 5%	490
	21st to end	Day	40% 12% 19% 16% 10% 4	484
November	1st to 10th	Day	48% 13% 14% 14% 10% 3	200
	11th to 20th	Day	45% 7% 14% 14% 11% 10%	200
	21st to end	Day	45% 7% 15% 15% 10% 10%	200
December	1st to 10th	Day	47% 7% 10% 12% 12% 12%	182
	11th to 20th	Day	51% 7% 9% 18% 13% 2	180
	21st to end	Day	47% 6% 17% 19% 8% 4	198
January	1st to 10th	Night	56% 6% 11% 14% 11% 2	850
	11th to 20th	Night	49% 6% 9% 19% 14% 2	850
	21st to end	Night	47% 5% 10% 21% 13% 4	842
February	1st to 10th	Night	45% 5% 12% 25% 12% 1	760
	11th to 20th	Night	44% 6% 13% 24% 13% 1	744
	21st to end	Night	46% 5% 12% 24% 10% 2	628
March	1st to 10th	Night	42% 8% 15% 21% 13% 2	760
	11th to 20th	Night	45% 5% 13% 24% 11% 3	760
	21st to end	Night	47% 5% 12% 24% 11% 1	836
April	1st to 10th	Night	42% 6% 12% 25% 13% 3	760
	11th to 20th	Night	36% 7% 13% 28% 13% 2	615
	21st to end	Night	36% 5% 12% 27% 16% 3	570
May	1st to 10th	Night	29% 3 14% 29% 22% 3	434
	11th to 20th	Night	32% 3 11% 26% 23% 5%	374
	21st to end	Night	34% 4 10% 27% 21% 5%	411
June	1st to 10th	Night	31% 4 11% 26% 24% 3	380
	11th to 20th	Night	26% 6% 11% 39% 16% 4	380
	21st to end	Night	21% 3 11% 30% 29% 6%	380
July	1st to 10th	Night	15% 3 9% 34% 35% 3	370
	11th to 20th	Night	13% 3 13% 34% 30% 6%	368
	21st to end	Night	10% 4 12% 30% 38% 8%	416
August	1st to 10th	Night	16% 2 6% 23% 39% 14%	541
	11th to 20th	Night	12% 2 4 25% 40% 17%	564
	21st to end	Night	21% 3 10% 26% 33% 7%	655
September	1st to 10th	Night	15% 3 8% 34% 31% 9%	760
	11th to 20th	Night	25% 2 8% 25% 28% 12%	760
	21st to end	Night	27% 4 13% 26% 24% 7%	760
October	1st to 10th	Night	28% 2 10% 28% 27% 6%	760
	11th to 20th	Night	37% 4 10% 25% 17% 8%	760
	21st to end	Night	40% 5% 13% 25% 15% 3	836
November	1st to 10th	Night	50% 4 12% 24% 9%	780
	11th to 20th	Night	51% 5% 13% 18% 10% 3	800
	21st to end	Night	45% 5% 13% 21% 12% 4	800
December	1st to 10th	Night	38% 5% 10% 28% 16% 3	768
	11th to 20th	Night	49% 7% 14% 19% 8% 2	845
	21st to end	Night	54% 6% 13% 20% 7% 1	935

Page generated at 2024-11-29 07:43:09. Version ac07

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