Otter Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Otter Point clear sky chart from 2005-11-06 to 2025-10-04.

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	14% 9% 3 8% 5% 5% 5% 4 5% 7% 36%	130688
	Night	18% 10% 4 9% 6% 5% 5% 4 5% 7% 28%	127425
Transparency	Day	44% 10% 18% 19% 8% 1	130395
	Night	50% 10% 16% 17% 7% 1	127295
Seeing	Day	17% 10% 24% 27% 18% 4	16681
	Night	23% 8% 20% 26% 19% 4	24767

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	28% 15% 5% 11% 6% 6% 5% 4 5% 5% 11%	3179
	11th to 20th	Day	16% 10% 3 8% 6% 5% 4 3 5% 7% 31%	3159
	21st to end	Day	26% 12% 4 9% 6% 5% 4 3 4 5% 22%	4185
February	1st to 10th	Day	24% 13% 4 11% 7% 6% 4 5% 6% 5% 16%	1800
	11th to 20th	Day	24% 12% 4 10% 5% 5% 6% 3 5% 4 22%	1755
	21st to end	Day	20% 12% 3 10% 7% 6% 5% 5% 6% 6% 21%	1485
March	1st to 10th	Day	16% 15% 4 10% 7% 7% 6% 5% 6% 7% 18%	4773
	11th to 20th	Day	16% 13% 4 10% 6% 6% 5% 4 4 6% 27%	5000
	21st to end	Day	20% 12% 4 11% 7% 6% 6% 4 6% 6% 18%	5546
April	1st to 10th	Day	18% 12% 4 9% 7% 6% 5% 4 7% 8% 20%	2400
	11th to 20th	Day	15% 10% 3 8% 7% 5% 6% 5% 7% 6% 29%	2497
	21st to end	Day	16% 10% 3 8% 5% 5% 5% 5% 7% 7% 29%	2600
May	1st to 10th	Day	9% 7% 3 7% 5% 5% 4 3 5% 6% 46%	6315
	11th to 20th	Day	10% 8% 3 8% 5% 4 4 4 7% 9% 37%	6277
	21st to end	Day	14% 7% 3 7% 5% 6% 6% 4 7% 8% 34%	7033
June	1st to 10th	Day	12% 9% 3 7% 6% 5% 5% 5% 7% 8% 34%	3000
	11th to 20th	Day	10% 7% 3 9% 7% 7% 6% 4 6% 9% 33%	3000
	21st to end	Day	9% 6% 2 7% 6% 5% 5% 5% 6% 9% 42%	3000
July	1st to 10th	Day	4 3 1 4 3 3 4 3 4 5% 64%	6780
	11th to 20th	Day	3 3 1 3 2 3 4 3 4 6% 69%	6780
	21st to end	Day	5% 3 2 4 3 4 5% 3 6% 7% 59%	7011
August	1st to 10th	Day	3 2 1 3 3 3 4 4 6% 10% 60%	4363
	11th to 20th	Day	8% 6% 3 6% 4 5% 6% 4 6% 8% 44%	4156
	21st to end	Day	11% 7% 3 6% 4 4 4 4 5% 6% 45%	4584
September	1st to 10th	Day	7% 4 3 6% 5% 5% 5% 4 6% 8% 48%	2400
	11th to 20th	Day	11% 7% 3 6% 5% 4 5% 5% 6% 7% 41%	2349
	21st to end	Day	15% 6% 3 6% 5% 4 4 4 6% 7% 39%	2136
October	1st to 10th	Day	15% 8% 3 9% 5% 6% 6% 5% 6% 7% 29%	3211
	11th to 20th	Day	26% 10% 4 8% 4 4 4 3 5% 7% 25%	3161
	21st to end	Day	18% 10% 4 9% 6% 5% 6% 4 5% 7% 25%	3245
November	1st to 10th	Day	27% 13% 4 10% 6% 6% 5% 4 4 4 17%	1568
	11th to 20th	Day	24% 13% 3 11% 5% 7% 4 4 4 4 20%	1600
	21st to end	Day	26% 13% 4 10% 6% 5% 5% 4 6% 5% 18%	1600
December	1st to 10th	Day	15% 12% 4 11% 7% 6% 5% 3 6% 9% 23%	2597
	11th to 20th	Day	30% 15% 5% 9% 5% 5% 5% 4 5% 5% 13%	2645
	21st to end	Day	28% 18% 6% 11% 6% 5% 4 4 4 4 10%	3498
January	1st to 10th	Night	26% 17% 6% 12% 7% 5% 5% 3 4 4 11%	6766
	11th to 20th	Night	18% 10% 3 7% 4 4 4 4 5% 8% 33%	6739
	21st to end	Night	26% 13% 4 9% 5% 4 3 3 4 4 24%	6765
February	1st to 10th	Night	25% 14% 4 9% 6% 5% 5% 4 4 5% 18%	2600
	11th to 20th	Night	22% 14% 4 10% 6% 5% 3 3 4 5% 25%	2532
	21st to end	Night	24% 13% 4 9% 6% 4 5% 4 5% 5% 21%	2145
March	1st to 10th	Night	15% 13% 4 11% 7% 6% 6% 5% 6% 7% 21%	5118
	11th to 20th	Night	15% 11% 4 10% 6% 5% 5% 4 6% 6% 28%	4999
	21st to end	Night	24% 15% 5% 12% 6% 5% 5% 4 5% 5% 13%	5429
April	1st to 10th	Night	19% 12% 4 9% 6% 6% 5% 4 5% 7% 24%	2000
	11th to 20th	Night	15% 10% 3 8% 7% 5% 5% 5% 7% 7% 28%	1851
	21st to end	Night	16% 11% 3 9% 6% 5% 6% 4 6% 8% 26%	1800
May	1st to 10th	Night	11% 8% 3 8% 5% 4 3 3 5% 6% 45%	3645
	11th to 20th	Night	10% 12% 4 11% 7% 6% 6% 5% 6% 8% 26%	3616
	21st to end	Night	12% 8% 4 10% 7% 7% 7% 5% 7% 8% 25%	3839
June	1st to 10th	Night	12% 8% 4 9% 6% 6% 5% 5% 6% 7% 33%	1400
	11th to 20th	Night	11% 9% 3 8% 6% 7% 7% 5% 8% 9% 27%	1400
	21st to end	Night	6% 6% 3 7% 6% 6% 5% 4 7% 11% 40%	1400
July	1st to 10th	Night	4 5% 2 6% 5% 4 6% 2 4 7% 54%	3180
	11th to 20th	Night	2 3 1 4 4 5% 7% 4 4 7% 60%	3180
	21st to end	Night	4 5% 2 5% 5% 6% 9% 4 6% 8% 45%	3832
August	1st to 10th	Night	3 2 1 3 3 5% 7% 4 6% 12% 54%	2791
	11th to 20th	Night	8% 5% 2 5% 4 5% 7% 5% 6% 10% 44%	2902
	21st to end	Night	11% 6% 2 6% 5% 5% 5% 4 7% 10% 40%	3327
September	1st to 10th	Night	5% 4 2 6% 4 5% 5% 5% 6% 8% 51%	2000
	11th to 20th	Night	14% 6% 3 7% 5% 5% 5% 4 6% 8% 39%	2050
	21st to end	Night	14% 7% 3 8% 5% 4 4 4 6% 6% 39%	2263
October	1st to 10th	Night	13% 6% 3 7% 6% 6% 6% 4 7% 7% 34%	3836
	11th to 20th	Night	25% 10% 3 8% 4 4 4 3 5% 6% 28%	3777
	21st to end	Night	22% 9% 4 9% 5% 5% 6% 4 6% 6% 26%	4314
November	1st to 10th	Night	28% 13% 4 9% 6% 5% 5% 3 3 4 20%	2730
	11th to 20th	Night	27% 12% 4 10% 5% 5% 5% 4 5% 4 20%	2800
	21st to end	Night	25% 12% 5% 11% 6% 5% 5% 4 4 4 19%	2800
December	1st to 10th	Night	19% 10% 3 8% 6% 5% 6% 4 7% 9% 22%	4581
	11th to 20th	Night	29% 17% 6% 11% 6% 5% 5% 3 4 4 10%	5560
	21st to end	Night	28% 15% 5% 12% 6% 5% 5% 3 4 5% 12%	7458

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	72% 9% 7% 9% 2	3179
	11th to 20th	Day	53% 10% 19% 15% 2	3180
	21st to end	Day	64% 9% 9% 14% 4	4185
February	1st to 10th	Day	66% 10% 11% 8% 4 1	1800
	11th to 20th	Day	63% 10% 9% 13% 5%	1764
	21st to end	Day	62% 9% 13% 11% 5% 1	1485
March	1st to 10th	Day	57% 9% 14% 14% 4	4773
	11th to 20th	Day	54% 7% 15% 21% 3	5000
	21st to end	Day	62% 11% 15% 11% 2	5546
April	1st to 10th	Day	56% 13% 16% 13% 2	2400
	11th to 20th	Day	50% 10% 13% 17% 8% 1	2497
	21st to end	Day	48% 11% 16% 20% 5% 1	2600
May	1st to 10th	Day	36% 7% 18% 28% 10%	6315
	11th to 20th	Day	36% 12% 27% 22% 4	6280
	21st to end	Day	42% 11% 27% 16% 5%	7034
June	1st to 10th	Day	42% 12% 20% 18% 7% 1	3000
	11th to 20th	Day	41% 13% 22% 19% 4	3000
	21st to end	Day	35% 12% 24% 20% 8% 1	3000
July	1st to 10th	Day	19% 7% 22% 25% 20% 7%	6706
	11th to 20th	Day	13% 7% 22% 33% 24% 1	6699
	21st to end	Day	17% 11% 31% 29% 10% 1	6815
August	1st to 10th	Day	15% 12% 19% 37% 16% 1	4346
	11th to 20th	Day	33% 12% 28% 19% 7% 1	4195
	21st to end	Day	35% 9% 18% 28% 10%	4583
September	1st to 10th	Day	29% 11% 22% 23% 13% 2	2400
	11th to 20th	Day	38% 11% 16% 20% 13% 1	2349
	21st to end	Day	41% 10% 18% 20% 10% 1	2136
October	1st to 10th	Day	48% 9% 17% 20% 5%	3211
	11th to 20th	Day	57% 8% 13% 17% 5%	3161
	21st to end	Day	55% 9% 15% 14% 7% 1	3245
November	1st to 10th	Day	67% 8% 13% 9% 2 1	1568
	11th to 20th	Day	66% 8% 9% 11% 5% 1	1600
	21st to end	Day	66% 10% 8% 11% 4	1600
December	1st to 10th	Day	56% 11% 14% 15% 4	2597
	11th to 20th	Day	71% 9% 12% 7% 1	2648
	21st to end	Day	74% 9% 11% 5% 1	3498
January	1st to 10th	Night	73% 11% 7% 7% 2	6766
	11th to 20th	Night	48% 9% 18% 20% 4	6780
	21st to end	Night	61% 7% 10% 15% 6%	6765
February	1st to 10th	Night	65% 9% 12% 8% 5%	2600
	11th to 20th	Night	61% 8% 10% 14% 6% 1	2534
	21st to end	Night	61% 8% 12% 13% 5% 1	2145
March	1st to 10th	Night	53% 10% 14% 16% 6%	5118
	11th to 20th	Night	48% 10% 15% 23% 3 1	5000
	21st to end	Night	67% 9% 14% 9% 1	5429
April	1st to 10th	Night	55% 11% 17% 14% 4	2000
	11th to 20th	Night	49% 8% 15% 18% 6% 2	1851
	21st to end	Night	49% 10% 16% 16% 8% 1	1800
May	1st to 10th	Night	36% 7% 17% 28% 11%	3642
	11th to 20th	Night	41% 12% 23% 18% 6%	3616
	21st to end	Night	44% 13% 22% 18% 2	3839
June	1st to 10th	Night	43% 8% 20% 20% 8% 2	1400
	11th to 20th	Night	37% 13% 24% 22% 3	1400
	21st to end	Night	30% 12% 28% 20% 8% 3	1400
July	1st to 10th	Night	21% 8% 20% 26% 16% 8%	3145
	11th to 20th	Night	11% 10% 19% 33% 26% 1	3138
	21st to end	Night	20% 11% 26% 32% 10% 2	3723
August	1st to 10th	Night	13% 12% 19% 31% 23% 2	2783
	11th to 20th	Night	28% 11% 30% 20% 8% 3	2929
	21st to end	Night	33% 11% 16% 30% 10% 1	3327
September	1st to 10th	Night	24% 11% 19% 27% 14% 5%	2000
	11th to 20th	Night	38% 9% 15% 19% 15% 4	2050
	21st to end	Night	39% 8% 16% 22% 13% 1	2263
October	1st to 10th	Night	44% 8% 21% 21% 6% 1	3836
	11th to 20th	Night	55% 5% 17% 19% 5%	3777
	21st to end	Night	53% 9% 14% 15% 8% 1	4314
November	1st to 10th	Night	63% 8% 14% 11% 4	2730
	11th to 20th	Night	63% 9% 12% 10% 5% 2	2800
	21st to end	Night	65% 10% 10% 9% 6%	2800
December	1st to 10th	Night	56% 13% 11% 16% 4	4581
	11th to 20th	Night	74% 9% 11% 5% 2	5556
	21st to end	Night	70% 9% 11% 7% 2	7458

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	33% 20% 25% 15% 7% 2	200
	11th to 20th	Day	32% 14% 26% 20% 10% 1	200
	21st to end	Day	30% 13% 25% 20% 10% 2	320
February	1st to 10th	Day	32% 17% 26% 20% 5% 1	400
	11th to 20th	Day	30% 16% 26% 22% 6%	395
	21st to end	Day	24% 20% 27% 21% 7% 1	331
March	1st to 10th	Day	20% 14% 30% 24% 11% 1	498
	11th to 20th	Day	24% 14% 25% 21% 13% 3	500
	21st to end	Day	23% 13% 29% 23% 10% 1	550
April	1st to 10th	Day	20% 17% 27% 23% 11% 2	500
	11th to 20th	Day	17% 12% 31% 24% 12% 4	492
	21st to end	Day	19% 13% 26% 27% 13% 2	500
May	1st to 10th	Day	13% 11% 26% 30% 19% 2	503
	11th to 20th	Day	15% 8% 21% 30% 22% 4	528
	21st to end	Day	13% 9% 27% 29% 17% 5%	625
June	1st to 10th	Day	14% 9% 28% 29% 18% 2	730
	11th to 20th	Day	9% 12% 35% 30% 11% 2	730
	21st to end	Day	9% 7% 27% 30% 22% 5%	730
July	1st to 10th	Day	9% 5% 21% 34% 28% 4	721
	11th to 20th	Day	4 4 23% 37% 25% 7%	718
	21st to end	Day	4 3 19% 31% 34% 9%	634
August	1st to 10th	Day	5% 5% 16% 30% 34% 11%	527
	11th to 20th	Day	6% 3 14% 33% 35% 10%	517
	21st to end	Day	10% 4 18% 36% 26% 8%	583
September	1st to 10th	Day	11% 3 18% 36% 28% 4	530
	11th to 20th	Day	14% 7% 19% 28% 26% 7%	530
	21st to end	Day	17% 8% 22% 27% 22% 3	530
October	1st to 10th	Day	21% 9% 19% 25% 22% 5%	503
	11th to 20th	Day	29% 10% 18% 24% 17% 3	490
	21st to end	Day	23% 18% 26% 21% 10% 2	446
November	1st to 10th	Day	28% 17% 26% 25% 5%	200
	11th to 20th	Day	30% 11% 24% 23% 11% 2	200
	21st to end	Day	32% 13% 28% 13% 13% 4	200
December	1st to 10th	Day	25% 15% 21% 23% 15% 2	200
	11th to 20th	Day	38% 14% 22% 19% 7% 1	200
	21st to end	Day	38% 15% 25% 18% 4	220
January	1st to 10th	Night	36% 14% 22% 19% 8% 1	900
	11th to 20th	Night	31% 11% 18% 25% 14%	900
	21st to end	Night	31% 9% 21% 23% 14% 2	890
February	1st to 10th	Night	29% 15% 21% 24% 9% 2	800
	11th to 20th	Night	28% 11% 21% 27% 11% 1	784
	21st to end	Night	29% 16% 22% 20% 11% 3	660
March	1st to 10th	Night	24% 10% 21% 26% 16% 3	800
	11th to 20th	Night	26% 13% 23% 22% 14% 3	800
	21st to end	Night	27% 9% 23% 25% 14% 3	880
April	1st to 10th	Night	24% 10% 23% 24% 16% 3	800
	11th to 20th	Night	18% 9% 23% 32% 15% 3	663
	21st to end	Night	20% 8% 25% 28% 16% 3	600
May	1st to 10th	Night	13% 7% 19% 35% 22% 3	405
	11th to 20th	Night	14% 6% 18% 29% 27% 6%	394
	21st to end	Night	12% 6% 20% 35% 23% 3	433
June	1st to 10th	Night	17% 6% 21% 29% 27% 2	400
	11th to 20th	Night	13% 6% 31% 32% 17% 3	400
	21st to end	Night	10% 5% 20% 31% 29% 5%	400
July	1st to 10th	Night	6% 2 21% 32% 35% 5%	390
	11th to 20th	Night	4 2 18% 36% 34% 7%	388
	21st to end	Night	3 3 14% 33% 38% 10%	438
August	1st to 10th	Night	6% 2 11% 28% 39% 15%	502
	11th to 20th	Night	6% 1 9% 25% 43% 15%	594
	21st to end	Night	10% 2 16% 30% 35% 8%	703
September	1st to 10th	Night	7% 2 13% 34% 33% 11%	800
	11th to 20th	Night	15% 3 14% 26% 29% 13%	800
	21st to end	Night	17% 5% 18% 30% 23% 7%	800
October	1st to 10th	Night	20% 5% 15% 24% 28% 8%	772
	11th to 20th	Night	27% 6% 12% 26% 20% 8%	760
	21st to end	Night	29% 8% 19% 26% 15% 3	836
November	1st to 10th	Night	34% 9% 22% 24% 10%	780
	11th to 20th	Night	35% 11% 21% 20% 12% 1	800
	21st to end	Night	31% 9% 22% 23% 12% 2	800
December	1st to 10th	Night	28% 10% 19% 25% 16% 1	805
	11th to 20th	Night	35% 13% 23% 20% 7% 1	900
	21st to end	Night	33% 17% 26% 19% 5%	990

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