Shoal Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shoal Lake clear sky chart from 2005-11-06 to 2024-02-05.

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	11% 9% 4 8% 7% 4 5% 6% 6% 8% 33%	77743
	Night	9% 9% 4 9% 7% 4 6% 5% 6% 8% 33%	81106
Transparency	Day	48% 6% 15% 23% 8% 1	77459
	Night	48% 5% 13% 22% 10% 1	80971
Seeing	Day	14% 8% 30% 29% 15% 4	15128
	Night	13% 7% 32% 34% 13% 2	25274

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	4 16% 8% 13% 9% 6% 7% 9% 8% 6% 14%	2219
	11th to 20th	Day	3 8% 5% 15% 14% 6% 8% 8% 8% 11% 14%	2424
	21st to end	Day	8% 11% 4 11% 13% 3 7% 6% 6% 8% 22%	2794
February	1st to 10th	Day	8% 11% 5% 11% 11% 5% 6% 6% 8% 10% 20%	1472
	11th to 20th	Day	6% 9% 4 9% 9% 6% 10% 7% 7% 7% 25%	1572
	21st to end	Day	7% 9% 4 11% 11% 5% 7% 10% 7% 8% 22%	1480
March	1st to 10th	Day	11% 13% 6% 12% 11% 6% 6% 6% 6% 6% 17%	1800
	11th to 20th	Day	7% 10% 6% 10% 7% 5% 7% 6% 6% 8% 28%	1901
	21st to end	Day	10% 11% 4 10% 8% 4 5% 5% 6% 7% 28%	2276
April	1st to 10th	Day	7% 10% 3 8% 7% 5% 5% 5% 6% 8% 36%	2160
	11th to 20th	Day	12% 11% 5% 9% 7% 3 5% 5% 5% 6% 32%	2298
	21st to end	Day	14% 7% 3 6% 5% 4 5% 5% 5% 8% 37%	2340
May	1st to 10th	Day	13% 9% 3 6% 5% 3 5% 5% 6% 7% 39%	2474
	11th to 20th	Day	14% 8% 3 6% 5% 3 4 5% 6% 7% 39%	2588
	21st to end	Day	19% 8% 4 6% 6% 4 5% 5% 6% 8% 31%	2918
June	1st to 10th	Day	15% 6% 2 5% 5% 4 6% 6% 6% 8% 37%	2700
	11th to 20th	Day	19% 7% 3 5% 5% 3 5% 5% 6% 8% 34%	2700
	21st to end	Day	12% 6% 3 6% 6% 4 7% 6% 6% 8% 36%	2700
July	1st to 10th	Day	7% 4 2 5% 6% 4 5% 6% 6% 9% 47%	2700
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 6% 7% 10% 42%	2700
	21st to end	Day	7% 4 2 4 5% 3 5% 6% 7% 10% 50%	2755
August	1st to 10th	Day	9% 5% 2 6% 5% 3 5% 7% 6% 9% 44%	2507
	11th to 20th	Day	11% 5% 2 4 4 3 5% 6% 6% 7% 45%	2372
	21st to end	Day	11% 6% 3 5% 4 3 4 4 5% 8% 48%	2574
September	1st to 10th	Day	11% 4 2 5% 6% 3 4 5% 6% 7% 47%	2160
	11th to 20th	Day	13% 7% 3 5% 5% 3 4 4 6% 7% 43%	2015
	21st to end	Day	14% 6% 3 5% 5% 3 4 4 6% 7% 44%	1980
October	1st to 10th	Day	17% 12% 3 6% 5% 2 4 5% 5% 8% 34%	1926
	11th to 20th	Day	12% 11% 4 8% 5% 3 4 4 5% 7% 35%	1620
	21st to end	Day	12% 14% 6% 11% 7% 4 4 4 5% 6% 26%	1782
November	1st to 10th	Day	17% 13% 6% 9% 9% 4 4 4 4 5% 25%	1653
	11th to 20th	Day	9% 13% 6% 12% 10% 5% 5% 4 4 7% 25%	1402
	21st to end	Day	11% 13% 5% 10% 8% 4 5% 6% 5% 7% 28%	1330
December	1st to 10th	Day	7% 14% 7% 10% 12% 5% 8% 5% 8% 7% 18%	1330
	11th to 20th	Day	8% 13% 8% 15% 11% 5% 6% 6% 5% 7% 14%	1679
	21st to end	Day	5% 7% 4 7% 9% 5% 6% 6% 7% 10% 33%	2442
January	1st to 10th	Night	6% 12% 7% 13% 10% 5% 7% 7% 7% 7% 18%	4737
	11th to 20th	Night	5% 8% 5% 14% 13% 7% 8% 9% 9% 9% 14%	4479
	21st to end	Night	7% 11% 6% 15% 10% 5% 6% 6% 6% 7% 22%	4873
February	1st to 10th	Night	8% 11% 5% 10% 7% 4 7% 6% 7% 8% 26%	2583
	11th to 20th	Night	6% 9% 4 8% 8% 5% 7% 6% 7% 9% 31%	2290
	21st to end	Night	5% 8% 5% 10% 9% 4 8% 5% 7% 9% 31%	1776
March	1st to 10th	Night	11% 11% 5% 9% 7% 4 6% 6% 7% 8% 25%	2160
	11th to 20th	Night	5% 8% 5% 9% 7% 4 5% 5% 6% 8% 38%	2057
	21st to end	Night	9% 11% 5% 9% 6% 4 5% 5% 4 6% 35%	2080
April	1st to 10th	Night	5% 8% 3 9% 6% 4 5% 5% 6% 7% 42%	1800
	11th to 20th	Night	14% 12% 4 7% 6% 3 5% 5% 4 8% 32%	1613
	21st to end	Night	14% 7% 3 6% 6% 3 5% 5% 7% 7% 37%	1620
May	1st to 10th	Night	12% 7% 4 6% 4 3 6% 5% 5% 7% 40%	1483
	11th to 20th	Night	12% 8% 2 5% 5% 2 5% 4 6% 7% 44%	1305
	21st to end	Night	16% 6% 3 6% 5% 3 4 4 7% 8% 38%	1358
June	1st to 10th	Night	14% 5% 3 5% 4 4 5% 5% 7% 9% 41%	1260
	11th to 20th	Night	15% 4 2 5% 5% 3 4 6% 6% 9% 40%	1260
	21st to end	Night	10% 6% 2 6% 4 3 5% 4 7% 9% 44%	1260
July	1st to 10th	Night	8% 3 1 4 4 2 5% 5% 4 8% 56%	1260
	11th to 20th	Night	7% 3 2 4 5% 3 5% 5% 5% 7% 55%	1260
	21st to end	Night	5% 3 2 4 3 2 4 5% 6% 9% 57%	1561
August	1st to 10th	Night	5% 4 1 4 4 2 4 4 6% 10% 55%	1432
	11th to 20th	Night	8% 4 2 5% 4 2 4 4 6% 8% 54%	1528
	21st to end	Night	11% 4 2 4 4 2 3 3 4 8% 54%	1782
September	1st to 10th	Night	7% 5% 3 4 4 3 4 4 6% 7% 54%	1796
	11th to 20th	Night	13% 6% 2 5% 4 3 4 4 5% 7% 46%	1944
	21st to end	Night	12% 7% 4 5% 5% 3 4 4 5% 8% 43%	1980
October	1st to 10th	Night	12% 11% 3 6% 6% 2 4 4 5% 6% 41%	2013
	11th to 20th	Night	11% 9% 4 7% 5% 3 4 5% 6% 7% 39%	2340
	21st to end	Night	11% 10% 6% 9% 6% 4 5% 5% 5% 7% 32%	2574
November	1st to 10th	Night	12% 12% 5% 10% 8% 4 5% 4 6% 6% 27%	2424
	11th to 20th	Night	9% 12% 7% 12% 9% 5% 6% 5% 5% 6% 26%	2775
	21st to end	Night	10% 10% 5% 10% 9% 5% 6% 6% 6% 7% 27%	2850
December	1st to 10th	Night	6% 10% 5% 10% 11% 6% 9% 8% 7% 7% 21%	2850
	11th to 20th	Night	8% 13% 7% 16% 9% 5% 7% 6% 6% 6% 17%	3518
	21st to end	Night	6% 7% 4 8% 8% 6% 6% 5% 7% 9% 34%	5225

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	66% 6% 11% 14% 4	2219
	11th to 20th	Day	60% 5% 9% 21% 4	2448
	21st to end	Day	60% 5% 6% 22% 7%	2794
February	1st to 10th	Day	57% 5% 12% 18% 8%	1472
	11th to 20th	Day	54% 6% 10% 18% 11%	1581
	21st to end	Day	54% 7% 11% 17% 10%	1480
March	1st to 10th	Day	65% 7% 10% 13% 6%	1800
	11th to 20th	Day	53% 7% 12% 20% 8%	1903
	21st to end	Day	53% 6% 14% 18% 8%	2276
April	1st to 10th	Day	44% 6% 15% 24% 11% 1	2160
	11th to 20th	Day	52% 5% 12% 20% 11% 1	2298
	21st to end	Day	44% 6% 19% 22% 8% 1	2340
May	1st to 10th	Day	44% 4 15% 25% 11% 1	2474
	11th to 20th	Day	43% 6% 12% 26% 12% 1	2592
	21st to end	Day	51% 5% 13% 21% 9%	2918
June	1st to 10th	Day	45% 6% 17% 24% 8% 1	2700
	11th to 20th	Day	48% 6% 19% 17% 9% 1	2700
	21st to end	Day	44% 7% 18% 24% 6% 1	2700
July	1st to 10th	Day	31% 7% 21% 30% 9% 1	2626
	11th to 20th	Day	36% 7% 18% 28% 10% 1	2619
	21st to end	Day	29% 7% 21% 34% 9%	2602
August	1st to 10th	Day	36% 6% 21% 28% 9%	2491
	11th to 20th	Day	36% 7% 22% 28% 7%	2372
	21st to end	Day	36% 4 17% 34% 9%	2574
September	1st to 10th	Day	36% 5% 16% 31% 11% 1	2160
	11th to 20th	Day	41% 5% 18% 27% 9% 1	2015
	21st to end	Day	40% 4 13% 33% 9%	1980
October	1st to 10th	Day	49% 5% 15% 24% 6%	1926
	11th to 20th	Day	49% 5% 13% 26% 8%	1620
	21st to end	Day	59% 5% 13% 17% 5% 1	1782
November	1st to 10th	Day	63% 3 12% 15% 6% 1	1653
	11th to 20th	Day	61% 5% 15% 13% 6% 1	1402
	21st to end	Day	56% 6% 14% 19% 5%	1330
December	1st to 10th	Day	62% 6% 12% 14% 5% 1	1330
	11th to 20th	Day	68% 5% 11% 12% 3	1680
	21st to end	Day	44% 6% 10% 20% 18% 3	2442
January	1st to 10th	Night	61% 6% 11% 17% 5%	4737
	11th to 20th	Night	62% 6% 10% 16% 5%	4517
	21st to end	Night	60% 6% 10% 17% 7%	4873
February	1st to 10th	Night	54% 5% 10% 21% 9% 1	2583
	11th to 20th	Night	48% 5% 13% 20% 14% 1	2291
	21st to end	Night	49% 4 11% 24% 11%	1776
March	1st to 10th	Night	55% 6% 12% 20% 7%	2160
	11th to 20th	Night	44% 4 15% 26% 9% 1	2057
	21st to end	Night	49% 6% 13% 20% 12%	2080
April	1st to 10th	Night	40% 4 12% 24% 18% 2	1800
	11th to 20th	Night	51% 4 10% 22% 12% 1	1613
	21st to end	Night	44% 5% 15% 24% 10% 3	1620
May	1st to 10th	Night	43% 5% 14% 22% 16%	1483
	11th to 20th	Night	39% 5% 13% 27% 15% 2	1305
	21st to end	Night	43% 6% 14% 24% 12% 1	1358
June	1st to 10th	Night	39% 6% 17% 27% 10% 2	1260
	11th to 20th	Night	41% 8% 18% 20% 12% 1	1260
	21st to end	Night	36% 8% 22% 27% 6% 1	1260
July	1st to 10th	Night	26% 6% 21% 33% 12% 1	1225
	11th to 20th	Night	28% 6% 19% 33% 13% 1	1218
	21st to end	Night	24% 5% 22% 35% 13% 1	1474
August	1st to 10th	Night	25% 6% 23% 33% 13% 1	1424
	11th to 20th	Night	29% 5% 20% 35% 9% 2	1528
	21st to end	Night	30% 4 14% 37% 14% 1	1782
September	1st to 10th	Night	29% 5% 16% 34% 14% 2	1796
	11th to 20th	Night	38% 5% 15% 30% 11% 1	1944
	21st to end	Night	40% 4 13% 30% 11% 1	1980
October	1st to 10th	Night	44% 5% 17% 25% 9% 1	2013
	11th to 20th	Night	44% 5% 12% 28% 11%	2340
	21st to end	Night	52% 5% 13% 23% 7%	2574
November	1st to 10th	Night	57% 5% 13% 16% 7% 2	2424
	11th to 20th	Night	59% 6% 14% 16% 5% 1	2775
	21st to end	Night	55% 6% 17% 16% 6%	2850
December	1st to 10th	Night	57% 7% 14% 15% 7% 1	2850
	11th to 20th	Night	67% 5% 10% 13% 5%	3516
	21st to end	Night	46% 5% 11% 18% 17% 4	5225

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	11% 9% 30% 34% 14% 3	270
	11th to 20th	Day	4 7% 42% 36% 8% 3	270
	21st to end	Day	16% 7% 28% 29% 17% 2	297
February	1st to 10th	Day	12% 8% 34% 35% 11% 1	252
	11th to 20th	Day	8% 6% 34% 32% 16% 4	240
	21st to end	Day	5% 4 34% 33% 21% 3	198
March	1st to 10th	Day	12% 9% 31% 33% 12% 3	240
	11th to 20th	Day	11% 6% 35% 31% 15% 3	240
	21st to end	Day	16% 6% 33% 28% 14% 3	362
April	1st to 10th	Day	12% 12% 34% 29% 12% 2	420
	11th to 20th	Day	17% 10% 31% 29% 11% 2	576
	21st to end	Day	17% 8% 32% 30% 13% 1	600
May	1st to 10th	Day	14% 9% 29% 30% 15% 4	603
	11th to 20th	Day	17% 7% 29% 25% 16% 4	625
	21st to end	Day	19% 8% 26% 27% 16% 3	679
June	1st to 10th	Day	15% 10% 31% 26% 13% 6%	630
	11th to 20th	Day	19% 10% 31% 23% 14% 3	630
	21st to end	Day	11% 8% 25% 34% 19% 3	630
July	1st to 10th	Day	10% 5% 25% 34% 20% 5%	621
	11th to 20th	Day	11% 8% 30% 29% 17% 5%	618
	21st to end	Day	6% 7% 26% 32% 23% 7%	684
August	1st to 10th	Day	10% 5% 26% 32% 21% 6%	626
	11th to 20th	Day	10% 7% 25% 28% 23% 7%	615
	21st to end	Day	14% 6% 24% 36% 17% 4	693
September	1st to 10th	Day	12% 11% 36% 25% 13% 2	450
	11th to 20th	Day	17% 9% 31% 30% 11% 2	305
	21st to end	Day	19% 11% 31% 26% 12% 1	270
October	1st to 10th	Day	24% 8% 23% 29% 11% 4	270
	11th to 20th	Day	17% 11% 35% 23% 10% 4	270
	21st to end	Day	22% 9% 36% 24% 6% 3	297
November	1st to 10th	Day	25% 9% 24% 30% 11% 1	270
	11th to 20th	Day	14% 10% 39% 28% 7% 1	270
	21st to end	Day	15% 10% 39% 27% 7% 1	270
December	1st to 10th	Day	11% 7% 37% 26% 16% 3	270
	11th to 20th	Day	14% 8% 44% 26% 8% 1	270
	21st to end	Day	12% 5% 31% 33% 15% 4	297
January	1st to 10th	Night	11% 9% 34% 34% 10% 1	950
	11th to 20th	Night	13% 10% 33% 34% 9% 2	950
	21st to end	Night	13% 9% 37% 31% 9% 1	1045
February	1st to 10th	Night	14% 6% 35% 32% 11% 2	923
	11th to 20th	Night	10% 6% 33% 36% 12% 3	839
	21st to end	Night	8% 5% 29% 37% 17% 4	592
March	1st to 10th	Night	15% 6% 30% 33% 14% 2	720
	11th to 20th	Night	9% 6% 35% 34% 14% 2	617
	21st to end	Night	14% 5% 31% 35% 11% 4	594
April	1st to 10th	Night	9% 7% 35% 35% 14% 1	540
	11th to 20th	Night	17% 7% 33% 32% 10% 1	533
	21st to end	Night	18% 5% 33% 33% 10% 1	540
May	1st to 10th	Night	16% 6% 29% 35% 12% 2	540
	11th to 20th	Night	16% 6% 27% 34% 16% 1	531
	21st to end	Night	19% 5% 28% 34% 14% 1	584
June	1st to 10th	Night	14% 6% 31% 33% 15% 1	540
	11th to 20th	Night	16% 5% 31% 34% 14% 1	540
	21st to end	Night	13% 5% 26% 37% 18% 1	540
July	1st to 10th	Night	9% 3 24% 43% 21%	525
	11th to 20th	Night	8% 4 30% 39% 16% 2	522
	21st to end	Night	6% 4 22% 46% 18% 3	591
August	1st to 10th	Night	6% 4 22% 46% 19% 2	537
	11th to 20th	Night	9% 5% 20% 37% 23% 5%	534
	21st to end	Night	15% 4 24% 39% 17% 1	594
September	1st to 10th	Night	10% 5% 30% 33% 18% 3	540
	11th to 20th	Night	16% 7% 29% 36% 12%	540
	21st to end	Night	14% 6% 30% 36% 13% 1	540
October	1st to 10th	Night	17% 5% 31% 34% 12% 1	573
	11th to 20th	Night	17% 7% 29% 33% 11% 2	900
	21st to end	Night	16% 10% 34% 31% 9% 1	990
November	1st to 10th	Night	17% 11% 36% 25% 10% 1	925
	11th to 20th	Night	15% 9% 40% 26% 9% 2	950
	21st to end	Night	14% 12% 37% 29% 7% 1	950
December	1st to 10th	Night	11% 6% 35% 31% 13% 3	950
	11th to 20th	Night	16% 9% 34% 29% 11% 1	950
	21st to end	Night	13% 6% 32% 33% 14% 2	1045

Page generated at 2024-02-02 04:20:28. Version ac07

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