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 2024-11-05.

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	15% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	105553
	Night	18% 10% 4 9% 6% 5% 5% 4 5% 6% 28%	102111
Transparency	Day	44% 10% 17% 19% 8% 1	105302
	Night	50% 9% 15% 17% 7% 1	102008
Seeing	Day	17% 10% 24% 27% 19% 4	15491
	Night	23% 8% 19% 26% 19% 4	23631

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	30% 14% 5% 11% 6% 5% 4 3 5% 5% 12%	2219
	11th to 20th	Day	22% 14% 4 9% 6% 5% 4 4 5% 5% 22%	2199
	21st to end	Day	32% 15% 5% 11% 7% 5% 4 3 4 4 8%	2919
February	1st to 10th	Day	25% 14% 4 11% 7% 6% 4 4 6% 5% 15%	1710
	11th to 20th	Day	24% 12% 4 11% 5% 5% 6% 3 5% 4 22%	1665
	21st to end	Day	19% 11% 3 10% 7% 6% 5% 5% 6% 6% 22%	1413
March	1st to 10th	Day	12% 13% 5% 10% 8% 7% 6% 6% 7% 8% 18%	3315
	11th to 20th	Day	14% 10% 4 9% 6% 5% 4 4 5% 6% 34%	3490
	21st to end	Day	19% 12% 4 10% 7% 5% 5% 3 6% 6% 23%	3872
April	1st to 10th	Day	19% 12% 4 9% 7% 6% 5% 4 7% 8% 20%	2280
	11th to 20th	Day	16% 11% 3 9% 7% 5% 6% 5% 7% 5% 27%	2370
	21st to end	Day	16% 10% 3 8% 6% 6% 5% 5% 7% 7% 27%	2470
May	1st to 10th	Day	11% 8% 3 7% 5% 4 4 3 5% 5% 43%	4415
	11th to 20th	Day	7% 6% 2 7% 5% 5% 5% 4 7% 10% 42%	4377
	21st to end	Day	17% 9% 3 8% 6% 6% 6% 4 5% 7% 29%	4901
June	1st to 10th	Day	13% 9% 3 8% 6% 5% 5% 5% 7% 8% 32%	2850
	11th to 20th	Day	10% 7% 3 9% 7% 7% 6% 4 6% 9% 33%	2850
	21st to end	Day	9% 6% 2 7% 6% 5% 5% 5% 6% 9% 42%	2850
July	1st to 10th	Day	4 3 1 4 3 2 3 3 4 5% 69%	4740
	11th to 20th	Day	3 3 1 2 2 3 4 3 5% 7% 68%	4740
	21st to end	Day	7% 4 2 4 3 3 4 3 6% 8% 55%	4885
August	1st to 10th	Day	3 2 1 3 3 3 4 3 6% 10% 61%	4229
	11th to 20th	Day	7% 6% 3 6% 4 5% 6% 4 7% 8% 45%	4026
	21st to end	Day	11% 7% 3 7% 4 4 5% 4 5% 6% 45%	4443
September	1st to 10th	Day	8% 4 3 6% 5% 5% 5% 4 6% 8% 49%	2280
	11th to 20th	Day	12% 7% 3 6% 5% 4 5% 5% 6% 6% 41%	2232
	21st to end	Day	15% 6% 3 6% 5% 4 4 4 6% 7% 39%	2029
October	1st to 10th	Day	14% 8% 3 9% 5% 6% 6% 5% 6% 7% 30%	3180
	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	28% 13% 4 9% 6% 6% 6% 4 4 4 17%	1520
	11th to 20th	Day	25% 13% 3 10% 6% 7% 4 4 4 4 20%	1520
	21st to end	Day	26% 13% 4 9% 6% 5% 5% 4 6% 4 18%	1520
December	1st to 10th	Day	19% 14% 3 10% 7% 5% 5% 4 5% 6% 23%	1511
	11th to 20th	Day	26% 14% 5% 9% 6% 5% 5% 4 5% 5% 15%	1685
	21st to end	Day	26% 15% 6% 12% 7% 6% 4 4 5% 5% 12%	2442
January	1st to 10th	Night	27% 18% 5% 12% 7% 5% 5% 3 4 3 11%	4726
	11th to 20th	Night	25% 12% 4 8% 5% 4 4 3 5% 7% 24%	4699
	21st to end	Night	35% 15% 5% 11% 5% 4 3 3 4 4 11%	4739
February	1st to 10th	Night	26% 14% 4 9% 6% 5% 4 4 4 5% 19%	2470
	11th to 20th	Night	21% 14% 4 10% 6% 5% 3 3 4 5% 25%	2402
	21st to end	Night	23% 13% 4 9% 6% 4 4 4 5% 5% 22%	2041
March	1st to 10th	Night	14% 13% 5% 11% 6% 6% 6% 4 6% 6% 21%	3556
	11th to 20th	Night	15% 8% 3 8% 5% 5% 5% 4 6% 7% 36%	3489
	21st to end	Night	20% 15% 5% 13% 6% 6% 5% 3 5% 5% 17%	3781
April	1st to 10th	Night	20% 12% 4 8% 6% 6% 5% 4 5% 7% 24%	1900
	11th to 20th	Night	15% 10% 3 9% 7% 6% 5% 5% 7% 7% 27%	1758
	21st to end	Night	17% 11% 3 10% 6% 5% 6% 4 6% 8% 25%	1710
May	1st to 10th	Night	13% 8% 3 7% 5% 4 4 4 5% 5% 43%	2545
	11th to 20th	Night	8% 10% 3 9% 6% 6% 5% 5% 6% 9% 33%	2516
	21st to end	Night	14% 10% 4 11% 7% 6% 6% 4 6% 7% 24%	2671
June	1st to 10th	Night	13% 8% 4 9% 6% 6% 5% 5% 6% 6% 32%	1330
	11th to 20th	Night	11% 9% 3 8% 6% 7% 7% 6% 8% 9% 26%	1330
	21st to end	Night	5% 6% 3 7% 6% 6% 5% 4 7% 11% 40%	1330
July	1st to 10th	Night	4 4 2 5% 5% 4 5% 3 4 7% 58%	2220
	11th to 20th	Night	2 3 1 3 4 4 6% 4 5% 8% 61%	2220
	21st to end	Night	6% 6% 3 6% 5% 6% 7% 4 6% 8% 43%	2667
August	1st to 10th	Night	2 2 1 3 3 4 7% 4 6% 12% 55%	2706
	11th to 20th	Night	8% 5% 2 5% 4 5% 7% 5% 6% 10% 44%	2812
	21st to end	Night	12% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	3226
September	1st to 10th	Night	5% 4 2 6% 4 4 5% 5% 6% 8% 52%	1900
	11th to 20th	Night	14% 6% 3 7% 5% 4 5% 4 6% 8% 38%	1947
	21st to end	Night	14% 7% 3 8% 5% 4 4 4 6% 7% 39%	2150
October	1st to 10th	Night	13% 6% 3 7% 6% 6% 6% 4 7% 7% 34%	3800
	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% 4 3 3 4 20%	2658
	11th to 20th	Night	27% 12% 4 10% 5% 5% 4 4 5% 4 21%	2660
	21st to end	Night	25% 11% 4 11% 6% 5% 5% 4 4 5% 20%	2660
December	1st to 10th	Night	23% 12% 3 8% 6% 5% 5% 3 5% 5% 24%	2667
	11th to 20th	Night	25% 15% 5% 11% 6% 5% 5% 4 5% 5% 13%	3520
	21st to end	Night	27% 15% 5% 12% 6% 5% 4 3 4 5% 13%	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	72% 9% 8% 9% 3	2219
	11th to 20th	Day	65% 8% 16% 8% 2	2220
	21st to end	Day	78% 8% 7% 6% 1	2919
February	1st to 10th	Day	67% 11% 11% 7% 4	1710
	11th to 20th	Day	63% 10% 10% 13% 4	1674
	21st to end	Day	61% 9% 14% 11% 5% 1	1413
March	1st to 10th	Day	53% 11% 17% 13% 5%	3315
	11th to 20th	Day	46% 8% 17% 26% 3 1	3490
	21st to end	Day	56% 11% 17% 12% 2	3872
April	1st to 10th	Day	56% 13% 16% 13% 2	2280
	11th to 20th	Day	51% 11% 13% 16% 8% 1	2370
	21st to end	Day	50% 11% 15% 18% 5% 1	2470
May	1st to 10th	Day	38% 8% 18% 27% 8%	4415
	11th to 20th	Day	29% 14% 28% 24% 5%	4380
	21st to end	Day	48% 12% 23% 14% 3	4902
June	1st to 10th	Day	44% 12% 19% 17% 7% 1	2850
	11th to 20th	Day	40% 14% 22% 19% 4	2850
	21st to end	Day	34% 12% 24% 20% 9% 1	2850
July	1st to 10th	Day	17% 7% 12% 28% 26% 11%	4666
	11th to 20th	Day	14% 7% 17% 36% 25% 1	4659
	21st to end	Day	21% 10% 25% 28% 14% 2	4731
August	1st to 10th	Day	15% 12% 18% 38% 17% 1	4212
	11th to 20th	Day	32% 12% 28% 19% 7% 1	4065
	21st to end	Day	36% 9% 18% 28% 9%	4442
September	1st to 10th	Day	29% 10% 21% 23% 14% 2	2280
	11th to 20th	Day	39% 11% 16% 19% 14% 1	2232
	21st to end	Day	41% 10% 18% 20% 10% 1	2029
October	1st to 10th	Day	48% 9% 18% 20% 5%	3180
	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	66% 8% 13% 10% 2 1	1520
	11th to 20th	Day	66% 8% 9% 11% 5% 1	1520
	21st to end	Day	66% 10% 8% 12% 4	1520
December	1st to 10th	Day	62% 8% 13% 13% 4	1511
	11th to 20th	Day	70% 9% 12% 7% 2	1688
	21st to end	Day	72% 9% 11% 6% 2	2442
January	1st to 10th	Night	72% 12% 8% 6% 3	4726
	11th to 20th	Night	61% 7% 15% 14% 2 1	4740
	21st to end	Night	75% 8% 7% 8% 2	4739
February	1st to 10th	Night	66% 9% 12% 8% 5%	2470
	11th to 20th	Night	60% 8% 11% 14% 6%	2404
	21st to end	Night	61% 7% 12% 13% 6% 1	2041
March	1st to 10th	Night	55% 11% 14% 16% 5%	3556
	11th to 20th	Night	39% 12% 18% 27% 2 1	3490
	21st to end	Night	62% 9% 16% 11% 1	3781
April	1st to 10th	Night	54% 11% 17% 14% 4	1900
	11th to 20th	Night	50% 9% 14% 18% 6% 2	1758
	21st to end	Night	51% 11% 14% 15% 8% 1	1710
May	1st to 10th	Night	36% 9% 18% 26% 10% 1	2545
	11th to 20th	Night	29% 14% 25% 22% 8%	2516
	21st to end	Night	46% 14% 20% 17% 3	2671
June	1st to 10th	Night	44% 9% 19% 20% 7% 2	1330
	11th to 20th	Night	38% 14% 25% 20% 3	1330
	21st to end	Night	29% 12% 27% 21% 8% 3	1330
July	1st to 10th	Night	19% 8% 11% 28% 22% 12%	2185
	11th to 20th	Night	12% 6% 16% 37% 28% 1	2178
	21st to end	Night	25% 8% 20% 30% 14% 2	2582
August	1st to 10th	Night	13% 11% 19% 32% 23% 2	2698
	11th to 20th	Night	27% 11% 31% 20% 8% 3	2839
	21st to end	Night	34% 11% 16% 30% 10%	3226
September	1st to 10th	Night	23% 10% 19% 28% 15% 5%	1900
	11th to 20th	Night	39% 9% 15% 18% 16% 4	1947
	21st to end	Night	39% 8% 16% 22% 13% 1	2150
October	1st to 10th	Night	43% 8% 21% 21% 6% 1	3800
	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	62% 8% 14% 11% 4	2658
	11th to 20th	Night	62% 9% 12% 10% 5% 2	2660
	21st to end	Night	65% 10% 10% 10% 6%	2660
December	1st to 10th	Night	62% 7% 13% 12% 5%	2667
	11th to 20th	Night	71% 10% 12% 4 3	3516
	21st to end	Night	69% 10% 11% 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	31% 21% 24% 16% 8% 2	180
	11th to 20th	Day	35% 13% 25% 17% 9% 1	180
	21st to end	Day	32% 14% 25% 21% 8% 1	293
February	1st to 10th	Day	32% 16% 25% 20% 5% 1	370
	11th to 20th	Day	29% 17% 25% 23% 6%	365
	21st to end	Day	21% 21% 27% 22% 7% 1	307
March	1st to 10th	Day	19% 14% 30% 24% 11% 1	458
	11th to 20th	Day	22% 13% 26% 22% 14% 3	460
	21st to end	Day	22% 13% 29% 25% 11% 1	506
April	1st to 10th	Day	20% 17% 26% 23% 12% 2	460
	11th to 20th	Day	18% 11% 31% 23% 13% 4	452
	21st to end	Day	20% 13% 27% 27% 12% 2	460
May	1st to 10th	Day	13% 10% 26% 31% 19% 2	463
	11th to 20th	Day	13% 7% 21% 32% 23% 4	488
	21st to end	Day	13% 7% 27% 30% 18% 5%	578
June	1st to 10th	Day	15% 9% 29% 28% 18% 2	680
	11th to 20th	Day	9% 11% 35% 30% 12% 2	680
	21st to end	Day	9% 6% 27% 30% 23% 5%	680
July	1st to 10th	Day	9% 4 20% 34% 29% 4	671
	11th to 20th	Day	4 4 22% 38% 26% 7%	668
	21st to end	Day	5% 3 18% 30% 34% 9%	587
August	1st to 10th	Day	5% 4 15% 29% 35% 12%	487
	11th to 20th	Day	5% 2 13% 34% 36% 11%	477
	21st to end	Day	10% 4 18% 35% 25% 7%	539
September	1st to 10th	Day	11% 3 19% 36% 26% 4	490
	11th to 20th	Day	15% 7% 19% 27% 26% 7%	490
	21st to end	Day	17% 7% 23% 27% 24% 3	490
October	1st to 10th	Day	21% 8% 19% 25% 22% 5%	490
	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	29% 17% 25% 24% 5%	188
	11th to 20th	Day	29% 9% 24% 24% 12% 2	180
	21st to end	Day	32% 13% 27% 11% 12% 4	180
December	1st to 10th	Day	27% 16% 21% 21% 14% 1	180
	11th to 20th	Day	35% 14% 23% 19% 8% 1	180
	21st to end	Day	36% 15% 25% 20% 4	198
January	1st to 10th	Night	37% 14% 21% 19% 9% 1	850
	11th to 20th	Night	32% 12% 17% 25% 14%	850
	21st to end	Night	32% 10% 20% 23% 14% 1	845
February	1st to 10th	Night	30% 14% 21% 24% 9% 2	760
	11th to 20th	Night	27% 12% 21% 27% 12% 1	744
	21st to end	Night	28% 15% 22% 20% 11% 3	628
March	1st to 10th	Night	24% 10% 21% 26% 16% 3	760
	11th to 20th	Night	25% 12% 23% 22% 15% 3	760
	21st to end	Night	27% 9% 22% 25% 14% 3	836
April	1st to 10th	Night	25% 9% 22% 25% 16% 3	760
	11th to 20th	Night	18% 9% 23% 32% 15% 3	630
	21st to end	Night	21% 9% 25% 28% 15% 2	570
May	1st to 10th	Night	14% 7% 19% 34% 23% 3	385
	11th to 20th	Night	13% 5% 17% 30% 29% 6%	374
	21st to end	Night	13% 5% 20% 36% 23% 3	411
June	1st to 10th	Night	17% 6% 21% 28% 26% 2	380
	11th to 20th	Night	13% 6% 29% 32% 17% 3	380
	21st to end	Night	9% 5% 21% 31% 29% 5%	380
July	1st to 10th	Night	6% 1 20% 33% 35% 5%	370
	11th to 20th	Night	4 2 17% 36% 34% 7%	368
	21st to end	Night	3 2 14% 32% 39% 10%	416
August	1st to 10th	Night	5% 1 10% 28% 40% 15%	477
	11th to 20th	Night	6% 7% 26% 44% 16%	564
	21st to end	Night	11% 1 16% 31% 33% 7%	668
September	1st to 10th	Night	7% 2 13% 33% 33% 11%	760
	11th to 20th	Night	15% 3 14% 26% 29% 14%	760
	21st to end	Night	17% 5% 17% 30% 24% 8%	760
October	1st to 10th	Night	20% 5% 14% 25% 28% 8%	760
	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% 23% 24% 11%	760
	11th to 20th	Night	34% 11% 21% 20% 12% 1	760
	21st to end	Night	31% 9% 22% 24% 12% 2	760
December	1st to 10th	Night	29% 10% 20% 25% 15% 1	764
	11th to 20th	Night	35% 13% 23% 21% 8% 1	850
	21st to end	Night	32% 16% 27% 20% 5%	935

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