Leitches Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leitches Creek clear sky chart from 2005-11-06 to 2025-05-11.

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	19% 12% 4 10% 6% 5% 5% 4 5% 6% 25%	113952
	Night	19% 12% 5% 11% 6% 5% 5% 4 5% 6% 24%	115159
Transparency	Day	59% 6% 12% 16% 6% 1	117461
	Night	59% 6% 12% 16% 6%	119824
Seeing	Day	27% 15% 31% 19% 7% 1	18341
	Night	26% 14% 30% 23% 6% 1	25791

By Month

Percentage Cloud Cover NE (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	12% 22% 7% 18% 7% 6% 4 3 4 4 13%	3616
	11th to 20th	Day	10% 17% 9% 17% 8% 6% 5% 3 5% 6% 14%	3591
	21st to end	Day	10% 11% 7% 17% 8% 7% 5% 3 6% 6% 22%	4026
February	1st to 10th	Day	17% 11% 5% 15% 8% 6% 6% 5% 6% 6% 15%	1800
	11th to 20th	Day	14% 14% 6% 11% 8% 6% 7% 4 6% 7% 18%	1765
	21st to end	Day	10% 15% 5% 10% 9% 5% 5% 3 5% 4 30%	1650
March	1st to 10th	Day	17% 13% 4 13% 8% 8% 4 3 4 4 23%	4474
	11th to 20th	Day	12% 17% 7% 11% 7% 6% 6% 4 5% 6% 19%	4904
	21st to end	Day	24% 17% 7% 12% 6% 4 4 3 4 4 15%	5823
April	1st to 10th	Day	21% 14% 4 9% 6% 5% 4 3 5% 5% 24%	2400
	11th to 20th	Day	21% 12% 4 7% 4 4 3 3 5% 5% 33%	2374
	21st to end	Day	24% 14% 3 7% 5% 3 4 3 5% 5% 27%	2579
May	1st to 10th	Day	28% 16% 3 7% 4 3 3 3 4 5% 24%	4565
	11th to 20th	Day	21% 12% 3 7% 4 4 4 3 5% 6% 30%	4398
	21st to end	Day	20% 10% 3 7% 4 5% 5% 4 6% 8% 29%	4836
June	1st to 10th	Day	30% 11% 3 7% 4 4 3 3 5% 7% 22%	2660
	11th to 20th	Day	19% 9% 3 7% 5% 4 4 3 5% 8% 33%	2660
	21st to end	Day	26% 11% 3 8% 6% 3 3 3 6% 6% 23%	2660
July	1st to 10th	Day	20% 9% 3 7% 6% 5% 5% 4 5% 8% 28%	4440
	11th to 20th	Day	15% 6% 3 8% 5% 5% 6% 5% 7% 9% 30%	4440
	21st to end	Day	15% 7% 3 6% 5% 5% 5% 4 7% 8% 36%	4815
August	1st to 10th	Day	17% 9% 3 8% 6% 5% 7% 5% 7% 8% 26%	4424
	11th to 20th	Day	21% 7% 3 8% 5% 5% 4 4 7% 8% 28%	4022
	21st to end	Day	13% 6% 3 7% 4 4 5% 4 6% 7% 40%	4180
September	1st to 10th	Day	19% 8% 2 6% 5% 4 5% 3 5% 8% 36%	2280
	11th to 20th	Day	20% 9% 3 6% 5% 4 5% 3 5% 6% 34%	2265
	21st to end	Day	19% 7% 2 7% 5% 4 4 3 5% 6% 37%	2052
October	1st to 10th	Day	20% 9% 3 7% 4 4 4 4 6% 8% 30%	1900
	11th to 20th	Day	20% 11% 4 9% 6% 5% 5% 4 6% 7% 25%	1900
	21st to end	Day	24% 15% 4 10% 5% 4 4 3 6% 5% 20%	1900
November	1st to 10th	Day	21% 16% 5% 8% 6% 5% 5% 3 5% 5% 21%	1760
	11th to 20th	Day	22% 21% 4 10% 6% 5% 5% 4 4 5% 14%	1605
	21st to end	Day	18% 20% 4 11% 6% 5% 5% 4 7% 5% 15%	1600
December	1st to 10th	Day	14% 16% 6% 13% 7% 6% 6% 4 5% 6% 18%	2610
	11th to 20th	Day	23% 18% 6% 14% 6% 4 3 4 4 4 14%	2996
	21st to end	Day	20% 15% 7% 17% 8% 5% 5% 3 3 4 12%	3982
January	1st to 10th	Night	17% 19% 7% 16% 6% 5% 5% 3 4 4 14%	6349
	11th to 20th	Night	15% 15% 9% 21% 8% 5% 5% 4 4 4 11%	6314
	21st to end	Night	9% 12% 6% 18% 12% 7% 6% 4 6% 5% 16%	6934
February	1st to 10th	Night	17% 13% 4 15% 8% 6% 6% 4 6% 5% 18%	2600
	11th to 20th	Night	16% 12% 4 12% 8% 7% 6% 4 5% 5% 21%	2520
	21st to end	Night	10% 14% 5% 14% 8% 5% 5% 3 5% 6% 24%	1980
March	1st to 10th	Night	19% 13% 5% 11% 7% 5% 5% 4 4 5% 23%	5366
	11th to 20th	Night	17% 15% 6% 10% 5% 5% 4 4 4 6% 25%	5053
	21st to end	Night	27% 14% 5% 11% 6% 5% 4 3 3 3 19%	5108
April	1st to 10th	Night	22% 12% 3 8% 6% 4 4 3 4 6% 27%	2000
	11th to 20th	Night	21% 11% 4 8% 4 3 3 3 5% 6% 33%	1976
	21st to end	Night	24% 11% 3 7% 4 4 3 3 3 4 32%	1816
May	1st to 10th	Night	28% 14% 3 6% 4 4 3 3 5% 6% 25%	2605
	11th to 20th	Night	19% 11% 3 7% 4 4 4 4 5% 6% 33%	2513
	21st to end	Night	18% 10% 3 7% 5% 5% 4 4 6% 9% 29%	2749
June	1st to 10th	Night	32% 11% 4 7% 4 3 4 3 5% 5% 22%	1520
	11th to 20th	Night	22% 7% 3 6% 4 3 4 3 5% 6% 36%	1520
	21st to end	Night	27% 9% 3 8% 5% 3 4 3 5% 7% 26%	1520
July	1st to 10th	Night	19% 9% 4 9% 5% 5% 6% 5% 5% 7% 26%	2530
	11th to 20th	Night	15% 9% 4 9% 5% 4 5% 5% 7% 8% 30%	2530
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 6% 7% 36%	2750
August	1st to 10th	Night	15% 8% 4 9% 6% 5% 5% 4 6% 8% 29%	2516
	11th to 20th	Night	17% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	2801
	21st to end	Night	15% 6% 2 5% 4 3 4 3 5% 8% 44%	3476
September	1st to 10th	Night	16% 7% 2 6% 4 4 4 4 5% 8% 40%	1900
	11th to 20th	Night	21% 7% 2 6% 4 3 4 4 5% 6% 39%	1914
	21st to end	Night	20% 8% 3 7% 5% 4 4 3 4 6% 37%	2123
October	1st to 10th	Night	19% 7% 2 8% 5% 4 5% 3 6% 8% 34%	2280
	11th to 20th	Night	22% 9% 3 6% 5% 4 4 4 5% 7% 31%	2280
	21st to end	Night	24% 12% 3 9% 5% 5% 4 4 5% 5% 24%	2697
November	1st to 10th	Night	19% 13% 4 8% 6% 6% 5% 4 5% 6% 24%	2538
	11th to 20th	Night	24% 17% 4 9% 6% 5% 5% 3 5% 6% 16%	2792
	21st to end	Night	22% 16% 4 9% 5% 5% 6% 4 6% 5% 18%	2800
December	1st to 10th	Night	16% 14% 6% 10% 6% 5% 4 4 5% 6% 25%	4580
	11th to 20th	Night	21% 15% 6% 12% 6% 5% 5% 4 4 4 18%	5213
	21st to end	Night	22% 14% 6% 14% 5% 5% 5% 3 4 4 18%	6996

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	71% 8% 10% 8% 3	3617
	11th to 20th	Day	68% 5% 13% 11% 2	3620
	21st to end	Day	59% 7% 10% 15% 8% 1	4026
February	1st to 10th	Day	66% 6% 10% 12% 6% 1	1800
	11th to 20th	Day	61% 7% 13% 13% 5% 1	1773
	21st to end	Day	56% 5% 10% 17% 10% 2	1650
March	1st to 10th	Day	64% 4 7% 16% 9% 1	4478
	11th to 20th	Day	65% 7% 12% 12% 4	4904
	21st to end	Day	72% 4 7% 11% 5% 1	5823
April	1st to 10th	Day	62% 5% 9% 14% 8% 2	2400
	11th to 20th	Day	54% 4 10% 20% 10% 2	2374
	21st to end	Day	60% 5% 10% 15% 10% 1	2579
May	1st to 10th	Day	64% 5% 11% 14% 5% 1	4580
	11th to 20th	Day	56% 4 15% 19% 6%	4402
	21st to end	Day	52% 7% 16% 18% 6% 1	4836
June	1st to 10th	Day	63% 5% 10% 16% 5%	2660
	11th to 20th	Day	51% 6% 14% 20% 9% 1	2660
	21st to end	Day	62% 6% 10% 14% 7%	2660
July	1st to 10th	Day	54% 7% 15% 15% 9%	4370
	11th to 20th	Day	48% 9% 18% 19% 6%	4364
	21st to end	Day	45% 7% 19% 23% 6%	4662
August	1st to 10th	Day	54% 9% 14% 18% 5%	4410
	11th to 20th	Day	51% 7% 14% 23% 4	4062
	21st to end	Day	41% 6% 13% 28% 11%	4180
September	1st to 10th	Day	47% 6% 13% 23% 10% 1	2280
	11th to 20th	Day	51% 5% 12% 23% 9% 1	2265
	21st to end	Day	47% 6% 12% 25% 10% 1	2052
October	1st to 10th	Day	57% 5% 12% 17% 8%	3160
	11th to 20th	Day	48% 6% 12% 24% 10%	3140
	21st to end	Day	58% 6% 12% 19% 5%	3122
November	1st to 10th	Day	63% 6% 11% 15% 4	1760
	11th to 20th	Day	70% 6% 10% 10% 4	1605
	21st to end	Day	66% 7% 12% 10% 4	1600
December	1st to 10th	Day	63% 6% 10% 15% 6%	2610
	11th to 20th	Day	71% 6% 10% 10% 3	2995
	21st to end	Day	74% 6% 11% 6% 2	3982
January	1st to 10th	Night	69% 7% 13% 9% 2	6349
	11th to 20th	Night	74% 6% 10% 8% 2	6360
	21st to end	Night	61% 9% 10% 13% 6%	6934
February	1st to 10th	Night	65% 7% 10% 12% 7% 1	2600
	11th to 20th	Night	63% 5% 11% 15% 5% 1	2523
	21st to end	Night	59% 6% 10% 14% 10% 1	1980
March	1st to 10th	Night	61% 4 7% 15% 11% 2	5375
	11th to 20th	Night	60% 5% 13% 13% 8% 1	5054
	21st to end	Night	70% 4 5% 14% 6% 1	5108
April	1st to 10th	Night	58% 5% 9% 16% 11% 1	2000
	11th to 20th	Night	53% 5% 10% 20% 11% 1	1976
	21st to end	Night	57% 4 9% 18% 11% 2	1816
May	1st to 10th	Night	60% 6% 14% 14% 6% 1	2610
	11th to 20th	Night	52% 4 15% 20% 8% 1	2514
	21st to end	Night	51% 8% 15% 20% 6%	2750
June	1st to 10th	Night	65% 4 9% 16% 6% 1	1520
	11th to 20th	Night	49% 5% 13% 20% 13%	1520
	21st to end	Night	59% 6% 11% 16% 7% 1	1520
July	1st to 10th	Night	55% 6% 15% 16% 8%	2491
	11th to 20th	Night	50% 8% 17% 16% 9% 1	2482
	21st to end	Night	47% 7% 16% 22% 8%	2663
August	1st to 10th	Night	52% 7% 17% 20% 4	2505
	11th to 20th	Night	48% 9% 20% 19% 4	2827
	21st to end	Night	39% 6% 15% 32% 8%	3475
September	1st to 10th	Night	43% 8% 14% 24% 11%	1900
	11th to 20th	Night	46% 5% 12% 26% 10% 1	1914
	21st to end	Night	49% 6% 10% 25% 9%	2123
October	1st to 10th	Night	51% 6% 13% 19% 11%	3800
	11th to 20th	Night	45% 8% 13% 27% 8%	3779
	21st to end	Night	53% 7% 14% 18% 8%	4435
November	1st to 10th	Night	59% 8% 13% 15% 5%	2538
	11th to 20th	Night	66% 8% 12% 11% 4	2792
	21st to end	Night	64% 9% 13% 11% 4	2800
December	1st to 10th	Night	56% 7% 11% 20% 6%	4580
	11th to 20th	Night	64% 7% 9% 14% 5% 1	5215
	21st to end	Night	67% 6% 12% 12% 2	6996

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	28% 22% 33% 13% 4	400
	11th to 20th	Day	29% 18% 33% 15% 5% 1	400
	21st to end	Day	22% 22% 39% 14% 3	440
February	1st to 10th	Day	28% 25% 30% 15% 3	400
	11th to 20th	Day	29% 28% 24% 16% 2 1	396
	21st to end	Day	18% 22% 37% 17% 4 1	331
March	1st to 10th	Day	25% 26% 30% 14% 5% 1	400
	11th to 20th	Day	19% 26% 33% 14% 7% 1	483
	21st to end	Day	32% 24% 26% 12% 5% 1	550
April	1st to 10th	Day	35% 27% 25% 9% 4	500
	11th to 20th	Day	30% 20% 32% 13% 4	492
	21st to end	Day	33% 15% 31% 16% 5% 1	598
May	1st to 10th	Day	38% 14% 27% 15% 5% 2	703
	11th to 20th	Day	27% 11% 30% 19% 10% 2	674
	21st to end	Day	25% 14% 36% 20% 5% 1	735
June	1st to 10th	Day	39% 10% 24% 20% 6% 1	680
	11th to 20th	Day	24% 11% 35% 21% 7% 1	680
	21st to end	Day	32% 9% 29% 20% 8% 1	680
July	1st to 10th	Day	22% 9% 34% 25% 9% 1	670
	11th to 20th	Day	19% 7% 35% 28% 10% 1	668
	21st to end	Day	24% 5% 30% 30% 9% 1	740
August	1st to 10th	Day	20% 4 34% 30% 10% 2	675
	11th to 20th	Day	23% 7% 32% 24% 12% 2	501
	21st to end	Day	19% 9% 34% 24% 10% 3	539
September	1st to 10th	Day	21% 10% 37% 23% 7% 2	490
	11th to 20th	Day	30% 10% 31% 20% 7% 2	482
	21st to end	Day	24% 11% 35% 18% 11% 2	390
October	1st to 10th	Day	25% 11% 31% 21% 11% 3	390
	11th to 20th	Day	22% 15% 32% 18% 10% 3	390
	21st to end	Day	27% 23% 30% 14% 6% 1	429
November	1st to 10th	Day	28% 21% 27% 16% 6% 2	395
	11th to 20th	Day	35% 19% 26% 16% 4 1	400
	21st to end	Day	32% 22% 28% 14% 4	400
December	1st to 10th	Day	31% 21% 31% 14% 3 1	400
	11th to 20th	Day	36% 22% 27% 13% 3	400
	21st to end	Day	24% 26% 29% 15% 4 1	440
January	1st to 10th	Night	25% 21% 32% 18% 4	900
	11th to 20th	Night	26% 21% 31% 18% 5%	900
	21st to end	Night	21% 21% 35% 18% 4	977
February	1st to 10th	Night	28% 16% 32% 21% 3	800
	11th to 20th	Night	24% 26% 32% 15% 3	783
	21st to end	Night	18% 19% 36% 20% 8%	660
March	1st to 10th	Night	26% 17% 33% 20% 5%	800
	11th to 20th	Night	23% 14% 34% 22% 7% 1	800
	21st to end	Night	28% 16% 31% 20% 5% 1	729
April	1st to 10th	Night	29% 18% 30% 21% 3	600
	11th to 20th	Night	26% 14% 30% 23% 5% 1	594
	21st to end	Night	33% 11% 30% 19% 8%	600
May	1st to 10th	Night	34% 10% 29% 17% 8% 2	600
	11th to 20th	Night	28% 7% 29% 25% 10% 1	565
	21st to end	Night	24% 10% 36% 23% 6%	616
June	1st to 10th	Night	36% 9% 26% 25% 5%	570
	11th to 20th	Night	25% 7% 33% 28% 7%	570
	21st to end	Night	29% 6% 31% 27% 6%	570
July	1st to 10th	Night	22% 6% 31% 31% 9% 1	556
	11th to 20th	Night	20% 6% 33% 34% 7%	552
	21st to end	Night	24% 5% 27% 35% 8%	623
August	1st to 10th	Night	18% 6% 26% 37% 12% 1	568
	11th to 20th	Night	22% 4 24% 36% 12% 1	562
	21st to end	Night	18% 6% 23% 41% 12%	627
September	1st to 10th	Night	19% 7% 30% 33% 10% 1	570
	11th to 20th	Night	24% 11% 25% 29% 10% 1	570
	21st to end	Night	24% 9% 34% 25% 8%	603
October	1st to 10th	Night	23% 9% 30% 29% 9%	760
	11th to 20th	Night	26% 9% 30% 25% 9% 2	760
	21st to end	Night	30% 15% 30% 18% 5% 1	936
November	1st to 10th	Night	28% 16% 30% 20% 5% 1	880
	11th to 20th	Night	33% 17% 30% 15% 5% 1	900
	21st to end	Night	31% 18% 29% 17% 3	900
December	1st to 10th	Night	30% 19% 29% 17% 5%	900
	11th to 20th	Night	34% 21% 28% 13% 3	900
	21st to end	Night	27% 21% 32% 17% 3 1	990

Page generated at 2025-05-08 10:33:55. Version ac07

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