Squirrel Cove
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Squirrel Cove clear sky chart from 2005-11-06 to 2024-11-25.

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	22% 8% 3 6% 4 4 4 3 5% 6% 35%	105720
	Night	28% 9% 3 7% 4 4 4 3 4 5% 29%	102359
Transparency	Day	27% 49% 8% 11% 5% 1	105461
	Night	31% 48% 8% 9% 3 1	102265
Seeing	Day	26% 11% 22% 24% 14% 2	15768
	Night	33% 8% 20% 24% 13% 1	23704

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% 14% 4 7% 4 4 3 3 5% 5% 11%	2219
	11th to 20th	Day	31% 14% 3 6% 5% 3 3 3 5% 7% 19%	2199
	21st to end	Day	58% 11% 3 6% 3 3 2 2 2 2 7%	2606
February	1st to 10th	Day	34% 13% 3 8% 4 5% 3 3 4 5% 18%	1710
	11th to 20th	Day	30% 10% 2 7% 6% 5% 4 3 4 5% 24%	1665
	21st to end	Day	27% 12% 4 6% 5% 5% 5% 3 5% 6% 24%	1413
March	1st to 10th	Day	24% 13% 3 9% 6% 5% 5% 4 6% 5% 20%	3272
	11th to 20th	Day	22% 10% 3 7% 6% 5% 4 4 5% 6% 28%	3490
	21st to end	Day	21% 11% 4 9% 5% 4 4 4 5% 6% 27%	3825
April	1st to 10th	Day	26% 11% 3 8% 5% 5% 5% 3 4 7% 24%	2294
	11th to 20th	Day	24% 9% 3 7% 5% 4 5% 3 5% 6% 30%	2438
	21st to end	Day	25% 10% 2 7% 4 5% 3 3 5% 6% 30%	2470
May	1st to 10th	Day	14% 8% 3 6% 4 4 4 4 5% 6% 41%	4419
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 11% 37%	4426
	21st to end	Day	24% 10% 3 7% 5% 4 5% 3 4 6% 29%	5161
June	1st to 10th	Day	19% 9% 3 6% 5% 4 4 5% 5% 7% 32%	2850
	11th to 20th	Day	13% 8% 3 9% 6% 4 5% 4 7% 8% 33%	2850
	21st to end	Day	17% 6% 2 6% 4 4 4 4 5% 7% 42%	2850
July	1st to 10th	Day	8% 3 1 3 3 2 3 3 4 5% 65%	4740
	11th to 20th	Day	6% 2 1 3 2 2 2 3 4 6% 70%	4740
	21st to end	Day	12% 5% 2 5% 4 4 4 3 5% 7% 49%	5138
August	1st to 10th	Day	5% 2 1 2 2 2 2 3 4 7% 71%	4254
	11th to 20th	Day	11% 5% 2 5% 3 4 5% 4 6% 8% 45%	4026
	21st to end	Day	15% 5% 2 5% 3 4 4 3 4 7% 47%	4521
September	1st to 10th	Day	12% 5% 2 5% 3 4 4 3 5% 5% 52%	2304
	11th to 20th	Day	23% 6% 2 5% 4 3 3 2 5% 6% 41%	2182
	21st to end	Day	27% 6% 2 5% 5% 4 5% 3 5% 6% 33%	2064
October	1st to 10th	Day	30% 10% 3 9% 6% 4 4 3 4 5% 23%	3180
	11th to 20th	Day	34% 6% 2 7% 5% 4 4 3 5% 7% 23%	3161
	21st to end	Day	33% 12% 4 8% 4 4 4 3 5% 5% 19%	3090
November	1st to 10th	Day	39% 10% 4 8% 5% 4 4 3 4 4 16%	1568
	11th to 20th	Day	37% 11% 3 7% 5% 5% 4 2 4 4 18%	1600
	21st to end	Day	39% 12% 3 8% 5% 3 4 3 3 4 17%	1538
December	1st to 10th	Day	34% 12% 3 7% 4 4 4 2 4 4 23%	1330
	11th to 20th	Day	45% 12% 3 8% 5% 4 3 3 3 3 12%	1685
	21st to end	Day	42% 13% 3 8% 5% 4 3 3 3 3 13%	2442
January	1st to 10th	Night	39% 14% 4 9% 5% 4 4 3 4 4 11%	4726
	11th to 20th	Night	34% 10% 3 6% 4 4 4 3 5% 5% 21%	4699
	21st to end	Night	52% 12% 3 6% 4 3 3 2 3 3 9%	5050
February	1st to 10th	Night	37% 11% 3 7% 5% 3 4 3 3 5% 19%	2470
	11th to 20th	Night	28% 12% 3 6% 4 4 3 3 5% 5% 28%	2402
	21st to end	Night	30% 13% 3 7% 4 3 4 3 4 4 26%	2041
March	1st to 10th	Night	28% 12% 4 9% 5% 5% 4 3 5% 5% 21%	3596
	11th to 20th	Night	19% 10% 3 8% 5% 5% 5% 4 5% 4 30%	3489
	21st to end	Night	27% 12% 3 8% 5% 4 4 3 4 4 25%	3828
April	1st to 10th	Night	27% 11% 3 7% 5% 4 4 3 5% 5% 25%	1883
	11th to 20th	Night	23% 10% 3 6% 6% 5% 5% 4 5% 7% 27%	1691
	21st to end	Night	26% 9% 3 8% 5% 4 4 4 5% 4 27%	1710
May	1st to 10th	Night	14% 6% 2 6% 4 3 4 4 5% 6% 45%	2540
	11th to 20th	Night	13% 6% 3 6% 4 4 4 4 6% 10% 40%	2467
	21st to end	Night	26% 10% 3 7% 4 4 5% 4 5% 6% 26%	2414
June	1st to 10th	Night	20% 12% 3 7% 4 3 5% 3 5% 6% 31%	1330
	11th to 20th	Night	16% 9% 4 7% 7% 5% 5% 4 5% 7% 31%	1330
	21st to end	Night	17% 6% 3 7% 5% 4 4 4 6% 6% 37%	1330
July	1st to 10th	Night	7% 5% 2 4 3 3 3 2 4 5% 64%	2220
	11th to 20th	Night	5% 3 1 2 2 2 2 3 5% 5% 69%	2220
	21st to end	Night	14% 4 2 4 3 3 4 3 5% 5% 52%	2414
August	1st to 10th	Night	5% 3 1 3 3 3 2 3 4 5% 69%	2676
	11th to 20th	Night	10% 5% 2 6% 4 5% 5% 3 6% 8% 45%	2812
	21st to end	Night	15% 6% 2 6% 4 4 3 3 5% 6% 47%	3146
September	1st to 10th	Night	10% 5% 2 6% 3 3 4 3 3 7% 53%	1876
	11th to 20th	Night	22% 6% 2 6% 4 5% 3 3 4 5% 41%	1995
	21st to end	Night	26% 7% 3 6% 4 3 3 2 4 5% 37%	2115
October	1st to 10th	Night	31% 9% 3 6% 4 4 3 3 4 5% 26%	3800
	11th to 20th	Night	36% 7% 3 6% 4 4 5% 3 4 6% 23%	3777
	21st to end	Night	31% 10% 3 8% 4 4 3 3 4 6% 22%	4466
November	1st to 10th	Night	41% 10% 3 8% 4 4 3 3 4 4 15%	2730
	11th to 20th	Night	35% 12% 4 8% 6% 4 4 2 4 4 18%	2800
	21st to end	Night	38% 11% 3 7% 5% 4 3 3 4 4 18%	2732
December	1st to 10th	Night	33% 12% 4 8% 4 3 3 3 4 5% 22%	2850
	11th to 20th	Night	48% 13% 4 6% 4 3 3 2 3 3 12%	3520
	21st to end	Night	45% 14% 4 7% 4 3 3 2 3 3 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	45% 40% 7% 7% 2	2219
	11th to 20th	Day	37% 40% 11% 6% 6% 1	2220
	21st to end	Day	56% 40% 2 2	2606
February	1st to 10th	Day	23% 66% 3 3 3 3	1710
	11th to 20th	Day	24% 66% 3 4 1 2	1674
	21st to end	Day	20% 66% 6% 4 3 1	1413
March	1st to 10th	Day	39% 46% 5% 6% 4	3272
	11th to 20th	Day	30% 44% 7% 17% 1	3490
	21st to end	Day	34% 46% 10% 7% 3	3825
April	1st to 10th	Day	23% 67% 3 4 3	2294
	11th to 20th	Day	22% 67% 5% 3 2 1	2438
	21st to end	Day	20% 67% 4 6% 3	2470
May	1st to 10th	Day	23% 44% 12% 15% 6%	4419
	11th to 20th	Day	22% 47% 13% 15% 2	4429
	21st to end	Day	35% 44% 8% 8% 5%	5162
June	1st to 10th	Day	17% 67% 6% 7% 2	2850
	11th to 20th	Day	14% 67% 7% 8% 4	2850
	21st to end	Day	17% 65% 6% 9% 2	2850
July	1st to 10th	Day	10% 37% 6% 22% 17% 7%	4666
	11th to 20th	Day	7% 37% 13% 29% 14% 1	4659
	21st to end	Day	26% 39% 13% 15% 6%	4976
August	1st to 10th	Day	7% 38% 7% 38% 10% 1	4237
	11th to 20th	Day	25% 44% 18% 9% 4	4065
	21st to end	Day	23% 41% 16% 16% 4	4520
September	1st to 10th	Day	16% 62% 6% 11% 4	2304
	11th to 20th	Day	21% 61% 6% 7% 5%	2182
	21st to end	Day	21% 62% 5% 7% 3 1	2064
October	1st to 10th	Day	45% 40% 7% 5% 2	3180
	11th to 20th	Day	39% 40% 7% 13% 1	3161
	21st to end	Day	44% 40% 6% 8% 2	3090
November	1st to 10th	Day	33% 58% 5% 2 2	1568
	11th to 20th	Day	29% 58% 5% 5% 3 1	1600
	21st to end	Day	29% 60% 4 3 3 1	1538
December	1st to 10th	Day	25% 61% 5% 5% 3	1330
	11th to 20th	Day	46% 49% 2 2 1	1688
	21st to end	Day	49% 41% 6% 2 1 1	2442
January	1st to 10th	Night	47% 39% 6% 5% 2 1	4726
	11th to 20th	Night	35% 41% 10% 6% 3 4	4740
	21st to end	Night	55% 40% 3 2	5050
February	1st to 10th	Night	24% 65% 2 3 4 2	2470
	11th to 20th	Night	24% 65% 4 3 2 1	2404
	21st to end	Night	20% 65% 4 6% 3 1	2041
March	1st to 10th	Night	37% 44% 7% 8% 4	3596
	11th to 20th	Night	30% 44% 6% 19% 1	3490
	21st to end	Night	39% 44% 7% 7% 4	3828
April	1st to 10th	Night	22% 66% 4 5% 2	1883
	11th to 20th	Night	22% 66% 4 5% 2 2	1691
	21st to end	Night	23% 66% 3 5% 3	1710
May	1st to 10th	Night	19% 42% 14% 18% 6%	2540
	11th to 20th	Night	19% 47% 19% 12% 3	2467
	21st to end	Night	35% 45% 9% 8% 2	2414
June	1st to 10th	Night	17% 67% 7% 7% 2	1330
	11th to 20th	Night	15% 67% 7% 7% 4	1330
	21st to end	Night	17% 64% 7% 10% 1 1	1330
July	1st to 10th	Night	12% 35% 8% 27% 15% 2	2185
	11th to 20th	Night	7% 37% 16% 31% 9%	2178
	21st to end	Night	25% 39% 12% 18% 5%	2337
August	1st to 10th	Night	6% 37% 6% 43% 8% 1	2669
	11th to 20th	Night	25% 43% 21% 8% 3	2839
	21st to end	Night	24% 40% 20% 13% 3	3146
September	1st to 10th	Night	16% 62% 8% 9% 5%	1876
	11th to 20th	Night	22% 62% 5% 6% 4 1	1995
	21st to end	Night	19% 61% 8% 7% 4	2115
October	1st to 10th	Night	42% 41% 9% 5% 3	3800
	11th to 20th	Night	43% 39% 10% 8% 1	3777
	21st to end	Night	40% 41% 9% 8% 2	4466
November	1st to 10th	Night	33% 58% 3 3 2	2730
	11th to 20th	Night	29% 59% 4 4 3 1	2800
	21st to end	Night	28% 60% 3 4 3 1	2732
December	1st to 10th	Night	27% 61% 4 6% 2	2850
	11th to 20th	Night	44% 50% 2 2 1 1	3516
	21st to end	Night	52% 39% 4 4 1 1	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	47% 6% 27% 12% 3 6%	180
	11th to 20th	Day	42% 18% 15% 14% 11% 1	180
	21st to end	Day	45% 12% 16% 16% 10% 1	274
February	1st to 10th	Day	42% 15% 21% 13% 8%	370
	11th to 20th	Day	32% 14% 26% 19% 7% 2	365
	21st to end	Day	34% 14% 27% 18% 7% 1	307
March	1st to 10th	Day	33% 11% 21% 21% 10% 3	429
	11th to 20th	Day	33% 15% 19% 19% 13% 2	460
	21st to end	Day	32% 15% 23% 19% 8% 2	506
April	1st to 10th	Day	33% 17% 23% 18% 7% 1	460
	11th to 20th	Day	27% 13% 27% 20% 11% 2	452
	21st to end	Day	29% 15% 24% 20% 10% 1	460
May	1st to 10th	Day	19% 11% 28% 29% 13%	463
	11th to 20th	Day	20% 8% 24% 31% 15% 2	510
	21st to end	Day	20% 11% 25% 29% 13% 1	735
June	1st to 10th	Day	26% 14% 25% 24% 10% 1	680
	11th to 20th	Day	18% 14% 28% 26% 13% 1	680
	21st to end	Day	18% 9% 23% 34% 14% 2	680
July	1st to 10th	Day	14% 8% 25% 31% 18% 3	671
	11th to 20th	Day	10% 7% 26% 34% 20% 3	668
	21st to end	Day	10% 6% 17% 35% 28% 3	739
August	1st to 10th	Day	11% 3 17% 33% 29% 7%	487
	11th to 20th	Day	8% 6% 18% 38% 26% 4	477
	21st to end	Day	16% 9% 21% 35% 18% 2	539
September	1st to 10th	Day	15% 9% 24% 29% 19% 3	490
	11th to 20th	Day	29% 8% 17% 22% 21% 3	490
	21st to end	Day	30% 9% 21% 22% 17% 1	490
October	1st to 10th	Day	30% 9% 22% 19% 16% 4	490
	11th to 20th	Day	39% 9% 19% 17% 13% 3	490
	21st to end	Day	36% 15% 20% 17% 10% 3	400
November	1st to 10th	Day	43% 12% 23% 15% 6% 2	200
	11th to 20th	Day	42% 13% 16% 9% 14% 7%	200
	21st to end	Day	46% 12% 17% 10% 9% 6%	188
December	1st to 10th	Day	42% 10% 16% 12% 13% 8%	180
	11th to 20th	Day	46% 12% 16% 12% 12% 3	180
	21st to end	Day	45% 8% 22% 20% 4 1	198
January	1st to 10th	Night	48% 10% 20% 13% 7% 2	850
	11th to 20th	Night	45% 8% 18% 20% 8%	850
	21st to end	Night	44% 7% 20% 18% 11% 1	923
February	1st to 10th	Night	43% 9% 22% 21% 5%	760
	11th to 20th	Night	34% 8% 21% 26% 10%	744
	21st to end	Night	36% 12% 24% 19% 7% 1	628
March	1st to 10th	Night	39% 10% 21% 18% 12% 1	760
	11th to 20th	Night	35% 13% 20% 20% 11% 1	760
	21st to end	Night	35% 11% 20% 20% 12% 1	836
April	1st to 10th	Night	33% 9% 21% 25% 11% 1	738
	11th to 20th	Night	31% 8% 25% 26% 10%	563
	21st to end	Night	32% 9% 25% 26% 8%	570
May	1st to 10th	Night	21% 7% 25% 32% 14% 1	380
	11th to 20th	Night	24% 6% 19% 34% 17% 1	374
	21st to end	Night	24% 7% 22% 32% 13% 1	411
June	1st to 10th	Night	25% 9% 21% 33% 12% 1	380
	11th to 20th	Night	18% 10% 23% 32% 17%	380
	21st to end	Night	19% 6% 23% 33% 18% 1	380
July	1st to 10th	Night	14% 6% 21% 34% 25% 1	370
	11th to 20th	Night	11% 4 19% 38% 26% 2	368
	21st to end	Night	10% 3 14% 40% 31% 1	416
August	1st to 10th	Night	11% 4 10% 36% 37% 2	462
	11th to 20th	Night	11% 3 17% 38% 28% 3	564
	21st to end	Night	17% 7% 15% 40% 21%	627
September	1st to 10th	Night	14% 4 17% 37% 25% 3	736
	11th to 20th	Night	24% 5% 14% 24% 28% 5%	760
	21st to end	Night	32% 7% 16% 25% 18% 2	760
October	1st to 10th	Night	30% 6% 19% 27% 17% 1	760
	11th to 20th	Night	38% 5% 17% 24% 14% 3	760
	21st to end	Night	40% 9% 20% 20% 9% 2	836
November	1st to 10th	Night	47% 10% 19% 18% 7%	780
	11th to 20th	Night	40% 11% 25% 17% 6% 2	800
	21st to end	Night	43% 9% 21% 17% 8% 2	783
December	1st to 10th	Night	37% 8% 22% 21% 9% 2	850
	11th to 20th	Night	49% 8% 19% 15% 8% 1	850
	21st to end	Night	47% 11% 23% 16% 3	935

Page generated at 2024-11-22 05:02:24. Version ac07

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