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 2024-01-15.

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	24% 8% 3 6% 5% 3 4 4 5% 6% 33%	74703
	Night	29% 9% 3 6% 5% 3 4 4 4 5% 28%	75084
Transparency	Day	53% 9% 14% 16% 7% 1	74384
	Night	60% 8% 12% 13% 6% 1	74922
Seeing	Day	26% 10% 22% 25% 14% 2	14556
	Night	34% 8% 20% 24% 13% 1	22669

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	44% 12% 4 7% 4 2 4 3 3 4 14%	1329
	11th to 20th	Day	34% 13% 4 7% 7% 3 4 4 5% 6% 14%	1288
	21st to end	Day	38% 14% 4 8% 6% 4 4 3 3 4 13%	1480
February	1st to 10th	Day	35% 12% 4 7% 4 4 4 4 4 5% 18%	1620
	11th to 20th	Day	31% 9% 3 6% 7% 4 4 4 4 6% 23%	1575
	21st to end	Day	27% 11% 4 5% 5% 3 5% 4 5% 6% 24%	1332
March	1st to 10th	Day	29% 11% 3 6% 5% 3 4 5% 6% 6% 23%	1870
	11th to 20th	Day	30% 11% 4 7% 5% 4 4 5% 5% 5% 20%	1980
	21st to end	Day	26% 11% 4 8% 6% 3 4 4 4 6% 24%	2178
April	1st to 10th	Day	26% 10% 4 6% 6% 3 6% 3 4 7% 24%	2173
	11th to 20th	Day	24% 8% 3 7% 5% 3 5% 5% 5% 6% 29%	2308
	21st to end	Day	26% 9% 2 6% 5% 4 4 3 5% 6% 31%	2340
May	1st to 10th	Day	17% 7% 3 5% 5% 3 5% 5% 6% 7% 37%	2519
	11th to 20th	Day	17% 7% 3 6% 5% 3 5% 5% 6% 8% 35%	2498
	21st to end	Day	17% 8% 4 5% 6% 4 4 5% 5% 7% 36%	2917
June	1st to 10th	Day	20% 8% 4 6% 5% 3 5% 5% 5% 7% 33%	2700
	11th to 20th	Day	14% 7% 3 8% 7% 3 5% 5% 7% 9% 33%	2700
	21st to end	Day	16% 5% 2 5% 4 3 4 5% 5% 7% 44%	2700
July	1st to 10th	Day	13% 5% 2 4 4 2 4 5% 4 7% 49%	2700
	11th to 20th	Day	10% 3 2 4 4 2 4 5% 6% 8% 51%	2700
	21st to end	Day	7% 4 2 2 3 2 4 4 5% 7% 60%	2938
August	1st to 10th	Day	9% 3 1 3 3 2 4 4 4 7% 59%	2425
	11th to 20th	Day	7% 4 1 3 3 3 4 5% 5% 8% 58%	2298
	21st to end	Day	13% 5% 2 4 4 3 4 5% 5% 9% 47%	2574
September	1st to 10th	Day	13% 4 2 5% 3 3 4 4 5% 6% 51%	2183
	11th to 20th	Day	23% 6% 2 4 4 2 3 3 4 6% 41%	2068
	21st to end	Day	26% 6% 2 4 5% 3 6% 4 5% 6% 34%	1956
October	1st to 10th	Day	25% 7% 2 6% 6% 3 3 3 5% 6% 34%	1800
	11th to 20th	Day	34% 7% 3 6% 6% 2 3 4 4 7% 24%	1800
	21st to end	Day	36% 7% 3 5% 6% 2 3 4 4 5% 24%	1783
November	1st to 10th	Day	38% 9% 4 7% 5% 3 4 4 4 4 16%	1488
	11th to 20th	Day	38% 10% 4 6% 5% 4 4 3 4 5% 18%	1520
	21st to end	Day	39% 10% 4 7% 5% 3 3 4 4 4 18%	1506
December	1st to 10th	Day	35% 10% 4 6% 4 3 3 3 4 4 23%	1330
	11th to 20th	Day	45% 12% 4 7% 6% 3 3 3 3 3 12%	1685
	21st to end	Day	42% 13% 4 7% 6% 3 3 3 3 3 13%	2442
January	1st to 10th	Night	41% 12% 4 7% 5% 3 4 3 3 3 15%	2836
	11th to 20th	Night	38% 11% 4 7% 5% 3 4 4 4 4 16%	2760
	21st to end	Night	35% 13% 4 7% 6% 3 4 4 4 4 16%	2872
February	1st to 10th	Night	38% 10% 4 7% 5% 2 4 4 3 4 19%	2340
	11th to 20th	Night	29% 11% 3 5% 5% 3 4 3 4 6% 28%	2272
	21st to end	Night	29% 11% 3 6% 5% 2 4 4 4 4 27%	1924
March	1st to 10th	Night	30% 10% 4 6% 5% 3 4 5% 5% 5% 23%	2087
	11th to 20th	Night	29% 11% 4 6% 5% 3 5% 4 5% 4 24%	1979
	21st to end	Night	29% 10% 3 7% 6% 4 5% 4 5% 6% 20%	2178
April	1st to 10th	Night	27% 10% 4 6% 5% 2 5% 4 5% 5% 26%	1785
	11th to 20th	Night	24% 9% 3 5% 6% 4 5% 5% 5% 7% 25%	1601
	21st to end	Night	26% 8% 4 7% 6% 2 5% 4 4 4 29%	1620
May	1st to 10th	Night	19% 7% 3 5% 5% 3 4 5% 5% 6% 39%	1440
	11th to 20th	Night	18% 8% 4 6% 6% 3 5% 7% 6% 7% 30%	1395
	21st to end	Night	19% 10% 3 6% 5% 3 5% 5% 4 7% 33%	1358
June	1st to 10th	Night	19% 10% 4 7% 5% 2 6% 4 5% 7% 32%	1260
	11th to 20th	Night	16% 7% 5% 7% 7% 3 6% 6% 5% 7% 31%	1260
	21st to end	Night	16% 5% 3 6% 6% 2 5% 5% 7% 7% 38%	1260
July	1st to 10th	Night	12% 6% 3 5% 5% 2 4 4 4 6% 49%	1260
	11th to 20th	Night	9% 4 3 3 5% 3 4 5% 6% 7% 50%	1260
	21st to end	Night	9% 4 2 3 3 2 4 4 4 5% 60%	1379
August	1st to 10th	Night	8% 4 2 3 6% 3 4 4 5% 5% 55%	1509
	11th to 20th	Night	9% 3 2 3 4 2 3 4 4 7% 58%	1602
	21st to end	Night	13% 5% 2 5% 5% 3 3 5% 5% 7% 46%	1782
September	1st to 10th	Night	10% 5% 2 5% 4 3 3 5% 3 7% 52%	1777
	11th to 20th	Night	22% 5% 3 4 5% 4 4 3 4 5% 41%	1890
	21st to end	Night	25% 7% 3 5% 4 2 3 3 4 5% 39%	2003
October	1st to 10th	Night	24% 7% 3 5% 3 3 3 3 5% 6% 38%	2160
	11th to 20th	Night	33% 6% 3 5% 5% 3 4 5% 4 6% 26%	2160
	21st to end	Night	36% 8% 2 5% 4 3 3 3 3 5% 26%	2571
November	1st to 10th	Night	40% 9% 4 7% 5% 3 3 4 4 5% 16%	2590
	11th to 20th	Night	35% 10% 4 7% 6% 2 5% 3 4 4 19%	2660
	21st to end	Night	38% 10% 3 7% 5% 3 4 4 4 4 19%	2670
December	1st to 10th	Night	33% 11% 5% 7% 5% 2 3 3 4 5% 22%	2850
	11th to 20th	Night	48% 12% 4 6% 4 2 3 2 3 3 12%	3520
	21st to end	Night	45% 13% 4 6% 5% 3 4 3 3 3 14%	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	76% 5% 7% 7% 4 1	1329
	11th to 20th	Day	72% 7% 10% 6% 3 2	1288
	21st to end	Day	77% 5% 9% 7% 1 1	1480
February	1st to 10th	Day	70% 9% 7% 6% 5% 3	1620
	11th to 20th	Day	64% 8% 10% 13% 5% 1	1584
	21st to end	Day	61% 9% 12% 10% 5% 2	1332
March	1st to 10th	Day	63% 9% 12% 12% 3	1870
	11th to 20th	Day	67% 9% 10% 9% 3 1	1980
	21st to end	Day	64% 9% 12% 13% 2	2178
April	1st to 10th	Day	64% 9% 13% 9% 5%	2173
	11th to 20th	Day	58% 10% 11% 13% 8%	2308
	21st to end	Day	58% 10% 12% 13% 7% 1	2340
May	1st to 10th	Day	48% 10% 17% 19% 6%	2519
	11th to 20th	Day	49% 9% 17% 19% 5% 1	2501
	21st to end	Day	49% 10% 15% 20% 6%	2918
June	1st to 10th	Day	53% 11% 14% 15% 5% 2	2700
	11th to 20th	Day	49% 16% 15% 14% 5%	2700
	21st to end	Day	42% 11% 17% 21% 8% 1	2700
July	1st to 10th	Day	36% 11% 19% 22% 10% 1	2626
	11th to 20th	Day	31% 10% 22% 29% 8% 1	2619
	21st to end	Day	24% 10% 20% 31% 12% 2	2775
August	1st to 10th	Day	28% 9% 20% 30% 12% 1	2408
	11th to 20th	Day	26% 10% 21% 27% 14% 2	2298
	21st to end	Day	36% 11% 22% 24% 6% 1	2574
September	1st to 10th	Day	36% 9% 18% 25% 11% 2	2183
	11th to 20th	Day	46% 8% 14% 17% 14% 2	2068
	21st to end	Day	50% 10% 15% 17% 8% 1	1956
October	1st to 10th	Day	53% 9% 13% 16% 9% 1	1800
	11th to 20th	Day	63% 8% 14% 12% 3	1800
	21st to end	Day	62% 9% 11% 12% 6%	1783
November	1st to 10th	Day	71% 9% 8% 6% 5% 1	1488
	11th to 20th	Day	71% 7% 9% 7% 5% 1	1520
	21st to end	Day	69% 9% 9% 9% 4 1	1506
December	1st to 10th	Day	65% 7% 11% 10% 5% 2	1330
	11th to 20th	Day	78% 6% 7% 4 4 1	1688
	21st to end	Day	75% 8% 9% 4 3 1	2442
January	1st to 10th	Night	76% 6% 6% 7% 4 1	2836
	11th to 20th	Night	72% 7% 10% 7% 4 1	2760
	21st to end	Night	71% 7% 10% 9% 3 1	2872
February	1st to 10th	Night	71% 6% 7% 7% 6% 2	2340
	11th to 20th	Night	63% 8% 12% 11% 6%	2274
	21st to end	Night	61% 6% 11% 14% 6% 2	1924
March	1st to 10th	Night	65% 7% 11% 12% 4 1	2087
	11th to 20th	Night	66% 9% 11% 10% 4 1	1980
	21st to end	Night	65% 9% 12% 11% 3	2178
April	1st to 10th	Night	61% 9% 14% 13% 3	1785
	11th to 20th	Night	59% 10% 9% 15% 7%	1601
	21st to end	Night	59% 8% 11% 15% 7%	1620
May	1st to 10th	Night	48% 8% 17% 21% 6%	1440
	11th to 20th	Night	50% 10% 16% 17% 6% 1	1395
	21st to end	Night	51% 8% 20% 15% 5%	1358
June	1st to 10th	Night	54% 9% 17% 13% 6% 1	1260
	11th to 20th	Night	51% 13% 19% 13% 5%	1260
	21st to end	Night	44% 11% 17% 20% 6% 2	1260
July	1st to 10th	Night	37% 9% 18% 23% 12% 1	1225
	11th to 20th	Night	30% 10% 28% 24% 8% 1	1218
	21st to end	Night	24% 8% 21% 33% 13% 2	1302
August	1st to 10th	Night	29% 8% 17% 31% 13% 2	1502
	11th to 20th	Night	27% 7% 25% 23% 15% 2	1602
	21st to end	Night	38% 9% 22% 26% 5%	1782
September	1st to 10th	Night	33% 9% 19% 27% 10% 1	1777
	11th to 20th	Night	47% 8% 11% 18% 14% 2	1890
	21st to end	Night	50% 8% 18% 14% 9% 1	2003
October	1st to 10th	Night	49% 9% 15% 17% 9% 1	2160
	11th to 20th	Night	59% 8% 16% 13% 3	2160
	21st to end	Night	62% 8% 11% 13% 6%	2571
November	1st to 10th	Night	73% 8% 8% 7% 5% 1	2590
	11th to 20th	Night	71% 7% 8% 8% 5% 1	2660
	21st to end	Night	68% 7% 9% 9% 5% 1	2670
December	1st to 10th	Night	66% 7% 11% 10% 6% 1	2850
	11th to 20th	Night	77% 7% 7% 6% 3 1	3516
	21st to end	Night	77% 6% 7% 7% 2 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	43% 17% 14% 14% 11% 1	168
	21st to end	Day	41% 12% 17% 17% 11% 1	248
February	1st to 10th	Day	44% 14% 22% 13% 6%	340
	11th to 20th	Day	33% 13% 27% 19% 7% 2	335
	21st to end	Day	32% 13% 29% 18% 7% 1	280
March	1st to 10th	Day	33% 11% 21% 22% 10% 3	392
	11th to 20th	Day	35% 15% 20% 18% 11% 1	420
	21st to end	Day	33% 15% 24% 18% 8% 1	462
April	1st to 10th	Day	34% 17% 23% 18% 8% 1	420
	11th to 20th	Day	29% 11% 26% 20% 12% 2	412
	21st to end	Day	29% 15% 24% 20% 11% 1	420
May	1st to 10th	Day	20% 11% 26% 30% 13%	423
	11th to 20th	Day	21% 7% 22% 32% 16% 2	468
	21st to end	Day	19% 10% 26% 30% 14% 1	680
June	1st to 10th	Day	25% 13% 26% 25% 10% 1	630
	11th to 20th	Day	18% 14% 29% 26% 12%	630
	21st to end	Day	17% 9% 23% 34% 15% 2	630
July	1st to 10th	Day	15% 8% 25% 31% 18% 3	621
	11th to 20th	Day	11% 8% 27% 33% 19% 2	618
	21st to end	Day	9% 6% 17% 35% 29% 3	684
August	1st to 10th	Day	12% 4 18% 34% 26% 6%	447
	11th to 20th	Day	8% 6% 19% 39% 26% 2	437
	21st to end	Day	16% 9% 21% 36% 17% 2	495
September	1st to 10th	Day	16% 10% 25% 31% 16% 2	450
	11th to 20th	Day	29% 8% 17% 22% 21% 3	450
	21st to end	Day	29% 9% 20% 22% 18% 2	450
October	1st to 10th	Day	29% 8% 23% 19% 16% 4	450
	11th to 20th	Day	39% 8% 19% 17% 14% 4	450
	21st to end	Day	36% 15% 20% 16% 10% 3	368
November	1st to 10th	Day	43% 11% 23% 14% 7% 2	180
	11th to 20th	Day	44% 13% 14% 8% 14% 7%	180
	21st to end	Day	46% 12% 16% 10% 9% 7%	180
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%	820
	21st to end	Night	42% 7% 20% 19% 12% 1	869
February	1st to 10th	Night	44% 9% 22% 20% 4	720
	11th to 20th	Night	35% 8% 21% 26% 10%	704
	21st to end	Night	35% 12% 24% 20% 8% 1	592
March	1st to 10th	Night	39% 10% 21% 18% 12% 1	720
	11th to 20th	Night	37% 13% 21% 19% 10% 1	720
	21st to end	Night	36% 10% 20% 21% 12% 1	792
April	1st to 10th	Night	33% 8% 21% 25% 12% 1	700
	11th to 20th	Night	32% 7% 24% 26% 11%	533
	21st to end	Night	31% 9% 25% 26% 8%	540
May	1st to 10th	Night	22% 7% 25% 31% 15% 1	360
	11th to 20th	Night	24% 5% 19% 33% 18% 1	354
	21st to end	Night	23% 7% 23% 33% 14% 1	389
June	1st to 10th	Night	24% 9% 20% 34% 12% 1	360
	11th to 20th	Night	19% 10% 23% 32% 16%	360
	21st to end	Night	18% 6% 24% 33% 19% 1	360
July	1st to 10th	Night	15% 5% 19% 33% 26% 1	350
	11th to 20th	Night	11% 5% 19% 37% 27% 1	348
	21st to end	Night	9% 3 14% 41% 32% 2	394
August	1st to 10th	Night	12% 4 10% 37% 35% 2	437
	11th to 20th	Night	11% 3 18% 38% 29% 2	534
	21st to end	Night	18% 6% 15% 41% 20% 1	594
September	1st to 10th	Night	15% 5% 17% 38% 23% 3	697
	11th to 20th	Night	25% 5% 13% 24% 28% 5%	720
	21st to end	Night	31% 7% 16% 24% 19% 2	720
October	1st to 10th	Night	30% 6% 19% 27% 17% 1	720
	11th to 20th	Night	38% 5% 17% 24% 14% 3	720
	21st to end	Night	41% 9% 20% 19% 8% 2	792
November	1st to 10th	Night	46% 9% 19% 18% 7%	740
	11th to 20th	Night	39% 10% 26% 17% 6% 2	760
	21st to end	Night	44% 9% 21% 17% 8% 2	765
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 2024-01-11 19:33:52. Version ac07

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