Lake Granby (North Shore)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Granby (North Shore) clear sky chart from 2005-11-06 to 2024-04-25.

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	4 10% 5% 9% 7% 3 4 4 5% 7% 41%	83439
	Night	3 10% 6% 9% 6% 3 4 4 4 6% 45%	85785
Transparency	Day	40% 8% 13% 21% 15% 4	83147
	Night	37% 8% 13% 23% 15% 4	85599
Seeing	Day	14% 20% 32% 22% 9% 2	14786
	Night	11% 14% 36% 26% 11% 1	24997

By Month

Percentage Cloud Cover SW (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	1 8% 8% 18% 16% 3 4 2 4 5% 31%	2538
	11th to 20th	Day	1 15% 11% 15% 13% 5% 3 3 4 5% 25%	2672
	21st to end	Day	1 13% 11% 18% 9% 2 3 2 3 4 33%	3146
February	1st to 10th	Day	1 17% 10% 16% 9% 3 3 3 3 6% 29%	1710
	11th to 20th	Day	2 14% 8% 15% 8% 4 4 4 4 4 35%	1770
	21st to end	Day	1 12% 9% 17% 12% 3 3 3 3 5% 32%	1570
March	1st to 10th	Day	2 11% 9% 14% 8% 2 3 4 3 6% 38%	3180
	11th to 20th	Day	1 10% 7% 9% 6% 3 3 3 4 8% 47%	3490
	21st to end	Day	3 15% 8% 17% 8% 3 5% 4 4 6% 27%	4000
April	1st to 10th	Day	5% 13% 5% 10% 6% 4 3 4 5% 8% 38%	2280
	11th to 20th	Day	6% 17% 6% 10% 7% 3 4 4 6% 7% 31%	2251
	21st to end	Day	6% 17% 6% 8% 5% 2 5% 6% 5% 6% 33%	2209
May	1st to 10th	Day	9% 15% 5% 7% 6% 3 5% 5% 6% 8% 32%	2304
	11th to 20th	Day	9% 11% 3 7% 7% 4 6% 7% 6% 8% 34%	2478
	21st to end	Day	7% 11% 3 7% 6% 4 6% 7% 7% 9% 34%	2724
June	1st to 10th	Day	6% 5% 2 4 5% 3 5% 6% 7% 9% 47%	2520
	11th to 20th	Day	7% 4 2 4 4 3 5% 5% 6% 8% 53%	2520
	21st to end	Day	4 3 2 5% 5% 3 5% 5% 6% 8% 53%	2520
July	1st to 10th	Day	7% 4 2 4 5% 4 6% 6% 7% 7% 47%	2520
	11th to 20th	Day	5% 4 2 4 5% 4 7% 6% 8% 7% 47%	2520
	21st to end	Day	7% 6% 3 6% 7% 5% 6% 6% 8% 8% 38%	2654
August	1st to 10th	Day	11% 6% 3 7% 6% 5% 5% 6% 7% 8% 38%	2328
	11th to 20th	Day	7% 5% 2 5% 6% 4 5% 6% 7% 7% 46%	2179
	21st to end	Day	7% 6% 3 5% 6% 4 7% 5% 7% 7% 43%	2376
September	1st to 10th	Day	7% 3 2 4 5% 4 4 4 6% 6% 56%	2160
	11th to 20th	Day	7% 6% 2 5% 4 3 4 4 5% 7% 55%	2160
	21st to end	Day	8% 6% 2 3 3 2 3 3 4 6% 61%	1950
October	1st to 10th	Day	6% 10% 4 6% 4 3 3 4 4 6% 51%	1800
	11th to 20th	Day	6% 10% 4 4 3 2 3 3 3 6% 57%	1800
	21st to end	Day	6% 13% 5% 7% 3 2 3 3 3 7% 49%	1948
November	1st to 10th	Day	3 11% 4 8% 3 2 2 3 5% 6% 54%	1673
	11th to 20th	Day	3 16% 6% 8% 5% 1 2 2 3 8% 46%	1710
	21st to end	Day	2 11% 6% 9% 5% 2 3 2 5% 7% 49%	1539
December	1st to 10th	Day	1 16% 7% 16% 7% 4 4 3 3 5% 34%	1520
	11th to 20th	Day	1 12% 8% 13% 7% 2 3 2 5% 10% 37%	1926
	21st to end	Day	1 12% 10% 16% 10% 5% 4 4 4 5% 31%	2794
January	1st to 10th	Night	1 9% 8% 16% 12% 6% 4 4 4 5% 30%	4417
	11th to 20th	Night	1 12% 12% 17% 8% 7% 2 2 3 4 32%	4328
	21st to end	Night	1 14% 10% 18% 8% 3 3 3 3 4 32%	4521
February	1st to 10th	Night	1 15% 9% 17% 10% 4 4 3 3 6% 29%	2470
	11th to 20th	Night	2 12% 9% 16% 7% 2 3 3 3 6% 36%	2296
	21st to end	Night	1 13% 8% 17% 10% 3 3 2 3 5% 35%	1884
March	1st to 10th	Night	1 11% 12% 10% 7% 2 3 3 4 5% 41%	3682
	11th to 20th	Night	1 12% 5% 8% 6% 3 3 3 4 6% 50%	3490
	21st to end	Night	2 16% 8% 11% 7% 3 4 4 4 5% 35%	3645
April	1st to 10th	Night	4 11% 6% 6% 6% 3 4 4 5% 6% 45%	1900
	11th to 20th	Night	3 13% 4 8% 7% 3 4 4 5% 6% 43%	1877
	21st to end	Night	6% 13% 4 6% 5% 2 3 4 4 7% 47%	1850
May	1st to 10th	Night	5% 11% 4 5% 5% 3 5% 5% 6% 8% 42%	1650
	11th to 20th	Night	6% 7% 2 5% 4 3 5% 6% 6% 9% 47%	1417
	21st to end	Night	5% 8% 3 4 4 3 4 5% 5% 8% 52%	1552
June	1st to 10th	Night	4 3 1 3 3 2 4 4 6% 10% 60%	1440
	11th to 20th	Night	5% 3 2 3 3 2 3 4 4 6% 65%	1440
	21st to end	Night	3 3 1 3 3 2 3 5% 8% 8% 61%	1440
July	1st to 10th	Night	4 3 1 3 4 3 5% 6% 7% 11% 54%	1440
	11th to 20th	Night	3 3 2 3 4 2 4 5% 7% 9% 60%	1440
	21st to end	Night	5% 4 2 4 5% 3 5% 6% 7% 9% 50%	1659
August	1st to 10th	Night	5% 4 2 5% 5% 3 5% 6% 6% 10% 51%	1611
	11th to 20th	Night	3 3 2 4 3 3 5% 6% 6% 8% 57%	1722
	21st to end	Night	4 3 2 4 5% 4 4 5% 6% 7% 57%	1980
September	1st to 10th	Night	5% 4 2 3 3 3 4 4 6% 7% 60%	1800
	11th to 20th	Night	5% 4 1 4 3 2 3 4 5% 8% 62%	1800
	21st to end	Night	5% 4 2 3 3 2 3 3 5% 6% 63%	2006
October	1st to 10th	Night	5% 8% 3 5% 3 3 3 4 5% 6% 56%	2160
	11th to 20th	Night	4 9% 3 3 3 2 2 2 3 5% 63%	2160
	21st to end	Night	6% 11% 4 7% 3 2 2 2 4 7% 51%	2389
November	1st to 10th	Night	2 12% 4 5% 3 2 2 2 4 6% 57%	2405
	11th to 20th	Night	2 15% 6% 8% 5% 1 2 2 3 6% 49%	2470
	21st to end	Night	2 10% 5% 9% 6% 3 3 4 3 7% 48%	2640
December	1st to 10th	Night	1 16% 6% 11% 7% 4 4 2 3 5% 40%	2660
	11th to 20th	Night	2 11% 7% 12% 7% 3 3 4 4 7% 39%	3271
	21st to end	Night	1 11% 8% 14% 10% 4 5% 4 5% 6% 32%	4873

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	48% 11% 12% 17% 10% 1	2539
	11th to 20th	Day	58% 9% 13% 12% 6% 1	2672
	21st to end	Day	45% 13% 13% 19% 9% 1	3146
February	1st to 10th	Day	58% 4 13% 14% 10% 1	1710
	11th to 20th	Day	51% 6% 9% 22% 10% 2	1779
	21st to end	Day	53% 5% 11% 13% 16% 2	1570
March	1st to 10th	Day	44% 5% 10% 26% 14% 1	3180
	11th to 20th	Day	34% 8% 19% 30% 8% 1	3490
	21st to end	Day	47% 13% 11% 23% 5% 1	4000
April	1st to 10th	Day	42% 7% 13% 19% 15% 4	2280
	11th to 20th	Day	49% 8% 12% 16% 14% 1	2254
	21st to end	Day	46% 7% 13% 24% 10% 1	2209
May	1st to 10th	Day	48% 8% 12% 18% 13% 1	2304
	11th to 20th	Day	45% 9% 15% 22% 8% 1	2482
	21st to end	Day	43% 8% 14% 19% 13% 3	2724
June	1st to 10th	Day	29% 9% 17% 22% 17% 7%	2520
	11th to 20th	Day	27% 7% 11% 19% 23% 13%	2520
	21st to end	Day	26% 6% 12% 21% 24% 12%	2520
July	1st to 10th	Day	31% 8% 12% 19% 21% 9%	2451
	11th to 20th	Day	30% 9% 13% 22% 16% 10%	2445
	21st to end	Day	39% 9% 15% 18% 15% 4	2506
August	1st to 10th	Day	40% 8% 14% 18% 13% 6%	2313
	11th to 20th	Day	33% 7% 12% 21% 20% 7%	2179
	21st to end	Day	35% 7% 12% 19% 19% 7%	2376
September	1st to 10th	Day	27% 4 10% 20% 27% 13%	2160
	11th to 20th	Day	27% 6% 12% 22% 24% 9%	2160
	21st to end	Day	26% 3 9% 29% 27% 5%	1950
October	1st to 10th	Day	33% 7% 11% 23% 20% 6%	1800
	11th to 20th	Day	29% 4 10% 32% 21% 4	1800
	21st to end	Day	35% 6% 13% 27% 16% 4	1948
November	1st to 10th	Day	30% 6% 14% 26% 22% 2	1673
	11th to 20th	Day	38% 5% 14% 24% 15% 3	1710
	21st to end	Day	35% 5% 15% 28% 14% 4	1539
December	1st to 10th	Day	52% 5% 15% 17% 10% 2	1520
	11th to 20th	Day	43% 7% 13% 29% 8%	1924
	21st to end	Day	48% 11% 8% 18% 13% 2	2794
January	1st to 10th	Night	49% 11% 11% 20% 7% 1	4417
	11th to 20th	Night	50% 12% 13% 13% 8% 3	4328
	21st to end	Night	49% 13% 13% 15% 10% 1	4521
February	1st to 10th	Night	56% 7% 11% 16% 9% 1	2470
	11th to 20th	Night	48% 6% 11% 24% 10% 1	2297
	21st to end	Night	50% 6% 9% 17% 15% 2	1884
March	1st to 10th	Night	40% 8% 9% 25% 17%	3682
	11th to 20th	Night	32% 11% 17% 30% 9% 1	3490
	21st to end	Night	41% 13% 14% 27% 5% 1	3645
April	1st to 10th	Night	38% 8% 13% 22% 16% 4	1900
	11th to 20th	Night	41% 8% 11% 25% 13% 2	1877
	21st to end	Night	37% 6% 15% 26% 15%	1850
May	1st to 10th	Night	37% 12% 15% 22% 13% 1	1650
	11th to 20th	Night	32% 13% 19% 28% 9%	1418
	21st to end	Night	29% 9% 18% 24% 18% 3	1552
June	1st to 10th	Night	18% 11% 20% 27% 18% 6%	1440
	11th to 20th	Night	19% 7% 12% 21% 25% 15%	1440
	21st to end	Night	16% 6% 14% 26% 24% 13%	1440
July	1st to 10th	Night	23% 11% 16% 22% 20% 9%	1400
	11th to 20th	Night	19% 8% 17% 28% 17% 11%	1392
	21st to end	Night	27% 10% 23% 21% 15% 4	1567
August	1st to 10th	Night	28% 10% 21% 21% 15% 6%	1602
	11th to 20th	Night	22% 9% 15% 21% 23% 10%	1722
	21st to end	Night	25% 7% 14% 25% 22% 8%	1980
September	1st to 10th	Night	23% 7% 13% 17% 28% 12%	1800
	11th to 20th	Night	21% 6% 12% 27% 22% 12%	1800
	21st to end	Night	22% 5% 10% 31% 26% 6%	2006
October	1st to 10th	Night	29% 7% 11% 27% 19% 7%	2160
	11th to 20th	Night	26% 4 12% 29% 23% 6%	2160
	21st to end	Night	33% 6% 15% 26% 17% 3	2389
November	1st to 10th	Night	28% 5% 13% 27% 23% 4	2405
	11th to 20th	Night	36% 4 14% 27% 16% 3	2470
	21st to end	Night	36% 6% 13% 28% 15% 2	2640
December	1st to 10th	Night	46% 6% 15% 20% 11% 2	2660
	11th to 20th	Night	43% 7% 15% 27% 9%	3272
	21st to end	Night	49% 8% 10% 20% 13% 1	4873

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	20% 18% 34% 17% 9% 1	270
	11th to 20th	Day	18% 29% 33% 17% 3 1	270
	21st to end	Day	9% 27% 43% 15% 6% 1	297
February	1st to 10th	Day	23% 35% 30% 10% 1 1	270
	11th to 20th	Day	22% 32% 33% 9% 3	270
	21st to end	Day	25% 34% 32% 8% 1	225
March	1st to 10th	Day	24% 27% 33% 14% 1	294
	11th to 20th	Day	17% 28% 34% 18% 3	460
	21st to end	Day	18% 41% 28% 10% 2	506
April	1st to 10th	Day	25% 30% 32% 10% 2	460
	11th to 20th	Day	25% 35% 26% 11% 2	452
	21st to end	Day	21% 29% 30% 15% 4 1	437
May	1st to 10th	Day	20% 26% 31% 17% 5%	499
	11th to 20th	Day	16% 17% 33% 24% 9% 1	625
	21st to end	Day	14% 18% 28% 26% 12% 2	679
June	1st to 10th	Day	7% 14% 30% 28% 16% 4	630
	11th to 20th	Day	10% 20% 33% 24% 11% 2	630
	21st to end	Day	6% 15% 35% 26% 16% 2	630
July	1st to 10th	Day	5% 7% 26% 37% 21% 4	621
	11th to 20th	Day	6% 6% 29% 34% 20% 5%	618
	21st to end	Day	7% 8% 26% 34% 21% 4	596
August	1st to 10th	Day	12% 10% 33% 32% 11% 3	447
	11th to 20th	Day	7% 10% 33% 34% 12% 4	437
	21st to end	Day	9% 11% 34% 29% 14% 3	495
September	1st to 10th	Day	10% 15% 33% 26% 12% 4	450
	11th to 20th	Day	8% 14% 40% 26% 10% 1	450
	21st to end	Day	10% 18% 27% 31% 11% 4	284
October	1st to 10th	Day	13% 16% 31% 22% 14% 4	270
	11th to 20th	Day	17% 22% 32% 19% 9% 1	270
	21st to end	Day	25% 24% 31% 15% 5%	297
November	1st to 10th	Day	20% 27% 33% 12% 7% 1	270
	11th to 20th	Day	19% 27% 35% 14% 4 1	270
	21st to end	Day	11% 24% 43% 19% 2 1	270
December	1st to 10th	Day	18% 25% 38% 13% 4 1	270
	11th to 20th	Day	14% 30% 40% 13% 3	270
	21st to end	Day	20% 22% 39% 15% 4 1	297
January	1st to 10th	Night	14% 21% 38% 19% 7% 1	950
	11th to 20th	Night	14% 25% 39% 16% 5% 1	887
	21st to end	Night	10% 19% 48% 17% 4	836
February	1st to 10th	Night	14% 23% 46% 13% 4	760
	11th to 20th	Night	12% 25% 44% 18% 2	744
	21st to end	Night	14% 25% 45% 13% 2	628
March	1st to 10th	Night	13% 18% 46% 17% 6%	760
	11th to 20th	Night	8% 15% 46% 25% 7%	760
	21st to end	Night	9% 20% 46% 21% 4 1	730
April	1st to 10th	Night	12% 20% 43% 22% 2	570
	11th to 20th	Night	11% 21% 42% 20% 5% 1	563
	21st to end	Night	13% 14% 38% 25% 8% 1	555
May	1st to 10th	Night	11% 12% 41% 25% 10% 1	540
	11th to 20th	Night	10% 8% 29% 39% 13% 1	531
	21st to end	Night	10% 10% 28% 37% 14% 1	584
June	1st to 10th	Night	5% 5% 29% 37% 21% 2	540
	11th to 20th	Night	8% 9% 30% 42% 10% 1	540
	21st to end	Night	4 5% 23% 44% 23% 1	540
July	1st to 10th	Night	5% 2 11% 45% 33% 4	525
	11th to 20th	Night	2 2 15% 43% 34% 3	522
	21st to end	Night	5% 2 9% 45% 35% 4	591
August	1st to 10th	Night	6% 2 13% 48% 30% 1	537
	11th to 20th	Night	3 1 17% 50% 25% 3	534
	21st to end	Night	4 2 15% 42% 33% 4	594
September	1st to 10th	Night	7% 4 20% 44% 22% 4	540
	11th to 20th	Night	5% 3 25% 44% 20% 3	540
	21st to end	Night	6% 6% 32% 36% 17% 4	581
October	1st to 10th	Night	11% 8% 37% 29% 13% 2	720
	11th to 20th	Night	13% 12% 38% 27% 9% 1	720
	21st to end	Night	14% 13% 44% 20% 7% 2	805
November	1st to 10th	Night	12% 17% 45% 19% 6% 1	925
	11th to 20th	Night	17% 21% 42% 16% 3 1	950
	21st to end	Night	11% 17% 45% 23% 4	950
December	1st to 10th	Night	15% 20% 46% 15% 3	950
	11th to 20th	Night	16% 23% 42% 16% 4	950
	21st to end	Night	17% 20% 42% 16% 5%	1045

Page generated at 2024-04-22 07:25:45. Version ac07

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