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 2026-09-14.

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 9% 6% 5% 5% 3 5% 6% 26%	149842
	Night	19% 12% 4 11% 6% 5% 5% 4 5% 6% 25%	141582
Transparency	Day	57% 6% 12% 18% 7%	153306
	Night	58% 6% 12% 17% 7%	146218
Seeing	Day	27% 16% 31% 18% 6% 1	20332
	Night	26% 14% 30% 23% 6% 1	27539

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% 20% 7% 19% 8% 6% 4 3 4 4 12%	4690
	11th to 20th	Day	14% 16% 9% 16% 8% 6% 5% 3 5% 5% 13%	4681
	21st to end	Day	10% 10% 6% 15% 10% 9% 5% 3 5% 6% 21%	5214
February	1st to 10th	Day	16% 12% 6% 15% 8% 6% 6% 5% 6% 6% 15%	1890
	11th to 20th	Day	14% 14% 6% 12% 8% 6% 6% 4 6% 6% 18%	1856
	21st to end	Day	10% 15% 5% 10% 9% 5% 5% 3 5% 4 30%	1730
March	1st to 10th	Day	17% 13% 4 13% 8% 8% 4 3 4 4 23%	4574
	11th to 20th	Day	12% 17% 7% 11% 7% 6% 6% 4 5% 6% 19%	5012
	21st to end	Day	24% 17% 7% 13% 6% 4 4 3 4 4 15%	5952
April	1st to 10th	Day	21% 14% 4 9% 5% 5% 4 3 5% 5% 24%	2520
	11th to 20th	Day	21% 12% 5% 7% 4 3 3 3 5% 5% 32%	2494
	21st to end	Day	24% 14% 3 7% 5% 3 4 3 5% 5% 28%	2708
May	1st to 10th	Day	25% 17% 3 7% 4 3 3 3 4 5% 26%	8236
	11th to 20th	Day	24% 11% 3 6% 4 4 4 3 4 6% 30%	8220
	21st to end	Day	24% 11% 3 7% 4 4 4 3 4 6% 32%	9059
June	1st to 10th	Day	28% 10% 3 7% 4 4 3 3 5% 7% 24%	2940
	11th to 20th	Day	19% 9% 3 6% 5% 4 5% 3 5% 8% 33%	2940
	21st to end	Day	25% 11% 3 8% 6% 4 3 4 5% 6% 24%	2940
July	1st to 10th	Day	17% 9% 4 8% 6% 5% 5% 4 6% 8% 29%	8280
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 4 6% 8% 39%	8280
	21st to end	Day	16% 7% 3 6% 5% 4 4 4 6% 7% 37%	8995
August	1st to 10th	Day	17% 9% 3 8% 6% 5% 6% 4 6% 7% 29%	6484
	11th to 20th	Day	19% 7% 3 9% 6% 6% 5% 4 7% 8% 27%	5916
	21st to end	Day	15% 7% 3 7% 4 5% 5% 4 6% 9% 36%	6080
September	1st to 10th	Day	19% 8% 2 6% 5% 4 5% 3 4 8% 36%	2520
	11th to 20th	Day	20% 9% 3 6% 5% 4 4 3 5% 6% 33%	2420
	21st to end	Day	18% 7% 2 7% 5% 4 4 3 5% 6% 38%	2160
October	1st to 10th	Day	20% 9% 3 7% 4 4 5% 4 6% 8% 31%	2000
	11th to 20th	Day	21% 11% 4 8% 6% 4 5% 4 5% 7% 25%	2000
	21st to end	Day	24% 15% 4 10% 6% 4 4 3 6% 5% 20%	2000
November	1st to 10th	Day	22% 16% 4 9% 6% 5% 5% 3 5% 5% 20%	1850
	11th to 20th	Day	22% 21% 4 10% 6% 5% 5% 4 4 5% 14%	1685
	21st to end	Day	18% 19% 4 11% 6% 6% 5% 4 7% 5% 15%	1680
December	1st to 10th	Day	14% 16% 6% 13% 7% 6% 6% 4 5% 6% 18%	2690
	11th to 20th	Day	23% 18% 6% 14% 6% 4 3 4 4 4 14%	3076
	21st to end	Day	20% 15% 7% 17% 8% 5% 5% 3 3 4 12%	4070
January	1st to 10th	Night	16% 16% 6% 15% 7% 5% 5% 4 5% 5% 16%	8234
	11th to 20th	Night	18% 14% 9% 20% 8% 6% 5% 3 4 4 10%	8234
	21st to end	Night	8% 11% 5% 19% 12% 9% 6% 4 5% 5% 15%	8980
February	1st to 10th	Night	17% 13% 4 15% 8% 6% 6% 4 5% 5% 17%	2730
	11th to 20th	Night	16% 12% 5% 12% 8% 7% 6% 4 5% 5% 21%	2649
	21st to end	Night	10% 14% 5% 15% 8% 5% 5% 3 5% 6% 24%	2076
March	1st to 10th	Night	19% 13% 5% 11% 6% 5% 5% 4 4 5% 24%	5486
	11th to 20th	Night	17% 15% 5% 10% 5% 5% 4 4 4 6% 24%	5165
	21st to end	Night	26% 14% 5% 11% 6% 5% 5% 3 3 3 19%	5221
April	1st to 10th	Night	22% 12% 3 8% 5% 4 4 3 3 6% 27%	2100
	11th to 20th	Night	21% 12% 4 8% 4 3 3 3 5% 5% 32%	2076
	21st to end	Night	24% 12% 3 7% 4 4 3 3 3 4 32%	1907
May	1st to 10th	Night	28% 14% 2 6% 3 3 3 3 5% 6% 25%	4692
	11th to 20th	Night	22% 13% 3 6% 3 4 4 4 5% 6% 32%	4670
	21st to end	Night	21% 10% 3 6% 4 4 4 4 5% 7% 32%	5147
June	1st to 10th	Night	30% 11% 4 7% 4 3 3 3 4 5% 25%	1680
	11th to 20th	Night	22% 7% 3 6% 4 3 4 4 5% 6% 36%	1680
	21st to end	Night	26% 10% 2 8% 5% 4 4 3 5% 7% 26%	1680
July	1st to 10th	Night	16% 8% 4 9% 6% 5% 5% 5% 6% 8% 28%	4709
	11th to 20th	Night	13% 8% 4 8% 4 4 5% 4 6% 7% 37%	4710
	21st to end	Night	17% 8% 3 7% 5% 4 4 4 6% 8% 35%	5116
August	1st to 10th	Night	18% 9% 3 8% 5% 4 5% 3 5% 7% 32%	3686
	11th to 20th	Night	18% 8% 3 8% 6% 5% 5% 4 6% 7% 30%	4126
	21st to end	Night	18% 7% 3 6% 4 4 4 3 5% 7% 39%	5045
September	1st to 10th	Night	17% 7% 3 6% 4 4 3 4 5% 7% 40%	2100
	11th to 20th	Night	20% 7% 2 6% 5% 3 4 4 5% 6% 39%	2046
	21st to end	Night	19% 7% 3 7% 5% 4 4 3 4 6% 38%	2235
October	1st to 10th	Night	19% 7% 2 8% 5% 4 5% 3 6% 8% 35%	2400
	11th to 20th	Night	22% 9% 3 6% 5% 4 5% 4 5% 7% 32%	2400
	21st to end	Night	24% 13% 3 9% 5% 5% 4 3 5% 5% 24%	2839
November	1st to 10th	Night	19% 13% 4 8% 6% 6% 5% 4 5% 6% 23%	2668
	11th to 20th	Night	25% 17% 4 9% 6% 5% 5% 3 5% 6% 16%	2932
	21st to end	Night	22% 16% 4 9% 5% 5% 6% 4 6% 6% 18%	2940
December	1st to 10th	Night	16% 13% 6% 10% 6% 5% 4 4 5% 6% 24%	4720
	11th to 20th	Night	21% 15% 6% 13% 6% 5% 5% 4 4 4 18%	5353
	21st to end	Night	22% 15% 6% 14% 5% 5% 5% 3 4 4 18%	7150

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	70% 8% 11% 8% 3	4691
	11th to 20th	Day	71% 5% 11% 10% 2	4710
	21st to end	Day	59% 6% 10% 15% 10% 1	5214
February	1st to 10th	Day	67% 6% 9% 12% 6% 1	1890
	11th to 20th	Day	61% 7% 12% 14% 5% 1	1864
	21st to end	Day	55% 5% 10% 17% 10% 2	1730
March	1st to 10th	Day	63% 4 7% 16% 9% 1	4578
	11th to 20th	Day	65% 7% 12% 12% 4	5012
	21st to end	Day	72% 4 7% 11% 5% 1	5952
April	1st to 10th	Day	61% 5% 9% 14% 9% 2	2520
	11th to 20th	Day	55% 4 9% 19% 10% 1	2494
	21st to end	Day	59% 5% 10% 15% 11% 1	2708
May	1st to 10th	Day	62% 5% 11% 16% 6%	8249
	11th to 20th	Day	56% 5% 13% 18% 8% 1	8224
	21st to end	Day	53% 5% 11% 21% 9%	9060
June	1st to 10th	Day	61% 5% 10% 18% 6% 1	2940
	11th to 20th	Day	51% 5% 14% 20% 8% 1	2940
	21st to end	Day	61% 6% 11% 14% 8% 1	2940
July	1st to 10th	Day	52% 7% 16% 15% 9%	8210
	11th to 20th	Day	42% 7% 16% 28% 7%	8204
	21st to end	Day	45% 7% 16% 25% 7%	8798
August	1st to 10th	Day	53% 8% 13% 20% 6%	6470
	11th to 20th	Day	52% 8% 16% 21% 3	5956
	21st to end	Day	43% 6% 16% 26% 8%	6080
September	1st to 10th	Day	48% 6% 13% 23% 10% 1	2520
	11th to 20th	Day	50% 5% 12% 23% 9% 1	2420
	21st to end	Day	46% 6% 12% 25% 11% 1	2160
October	1st to 10th	Day	56% 5% 13% 18% 9%	3260
	11th to 20th	Day	48% 6% 11% 24% 10%	3240
	21st to end	Day	58% 6% 12% 19% 5%	3222
November	1st to 10th	Day	64% 6% 11% 15% 4	1850
	11th to 20th	Day	70% 6% 10% 10% 4	1685
	21st to end	Day	66% 7% 12% 10% 4	1680
December	1st to 10th	Day	63% 6% 10% 16% 6%	2690
	11th to 20th	Day	71% 6% 10% 10% 3	3075
	21st to end	Day	74% 6% 11% 7% 2	4070
January	1st to 10th	Night	65% 7% 13% 12% 3	8234
	11th to 20th	Night	75% 5% 9% 8% 2	8280
	21st to end	Night	62% 8% 10% 12% 8% 1	8980
February	1st to 10th	Night	65% 7% 9% 12% 7% 1	2730
	11th to 20th	Night	63% 5% 11% 15% 5% 1	2652
	21st to end	Night	59% 6% 10% 14% 10% 1	2076
March	1st to 10th	Night	60% 4 8% 15% 11% 2	5495
	11th to 20th	Night	60% 5% 13% 13% 8% 1	5166
	21st to end	Night	70% 4 5% 14% 6% 1	5221
April	1st to 10th	Night	58% 5% 9% 16% 12% 1	2100
	11th to 20th	Night	53% 5% 10% 20% 11% 1	2076
	21st to end	Night	57% 4 8% 18% 11% 2	1907
May	1st to 10th	Night	59% 5% 13% 16% 7%	4697
	11th to 20th	Night	54% 4 12% 20% 9% 1	4671
	21st to end	Night	49% 7% 12% 21% 11%	5148
June	1st to 10th	Night	62% 4 9% 17% 8% 1	1680
	11th to 20th	Night	49% 5% 13% 20% 13%	1680
	21st to end	Night	57% 7% 12% 16% 8% 1	1680
July	1st to 10th	Night	52% 8% 15% 17% 9%	4671
	11th to 20th	Night	44% 7% 15% 25% 9% 1	4662
	21st to end	Night	47% 7% 13% 25% 8%	4999
August	1st to 10th	Night	51% 7% 17% 20% 5%	3675
	11th to 20th	Night	50% 9% 21% 18% 3	4152
	21st to end	Night	44% 6% 14% 28% 8%	5044
September	1st to 10th	Night	43% 8% 14% 24% 10%	2100
	11th to 20th	Night	46% 6% 12% 26% 10% 1	2046
	21st to end	Night	47% 6% 10% 26% 10%	2235
October	1st to 10th	Night	50% 6% 13% 19% 11%	3920
	11th to 20th	Night	45% 8% 13% 27% 8%	3899
	21st to end	Night	54% 7% 14% 18% 7%	4577
November	1st to 10th	Night	59% 8% 13% 14% 4	2668
	11th to 20th	Night	66% 8% 12% 11% 4	2932
	21st to end	Night	63% 9% 13% 11% 4	2940
December	1st to 10th	Night	56% 7% 11% 20% 6%	4720
	11th to 20th	Night	65% 7% 9% 14% 5% 1	5355
	21st to end	Night	68% 6% 12% 12% 2	7150

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% 34% 13% 3	430
	11th to 20th	Day	31% 18% 31% 14% 4 1	430
	21st to end	Day	23% 22% 38% 14% 3	473
February	1st to 10th	Day	28% 23% 30% 15% 3	430
	11th to 20th	Day	28% 27% 24% 16% 3 1	426
	21st to end	Day	19% 23% 36% 17% 4 1	355
March	1st to 10th	Day	25% 27% 29% 14% 4 1	430
	11th to 20th	Day	20% 27% 31% 14% 7% 1	521
	21st to end	Day	33% 24% 26% 11% 5% 1	594
April	1st to 10th	Day	36% 28% 25% 8% 3	540
	11th to 20th	Day	31% 21% 32% 12% 4	532
	21st to end	Day	33% 14% 31% 15% 5% 1	643
May	1st to 10th	Day	38% 15% 27% 14% 4 2	753
	11th to 20th	Day	30% 13% 28% 17% 9% 2	774
	21st to end	Day	26% 14% 35% 19% 5% 1	845
June	1st to 10th	Day	37% 10% 26% 20% 6% 1	780
	11th to 20th	Day	24% 13% 36% 19% 7% 1	780
	21st to end	Day	31% 11% 30% 19% 8% 1	780
July	1st to 10th	Day	21% 9% 35% 25% 9% 1	770
	11th to 20th	Day	18% 10% 35% 28% 9% 1	768
	21st to end	Day	24% 7% 31% 29% 9% 1	850
August	1st to 10th	Day	20% 5% 33% 29% 11% 2	775
	11th to 20th	Day	22% 7% 33% 25% 11% 2	583
	21st to end	Day	18% 11% 37% 23% 9% 3	627
September	1st to 10th	Day	23% 10% 36% 23% 7% 2	570
	11th to 20th	Day	30% 11% 30% 19% 8% 2	533
	21st to end	Day	24% 11% 36% 17% 10% 2	420
October	1st to 10th	Day	24% 11% 31% 22% 10% 2	420
	11th to 20th	Day	22% 15% 32% 18% 10% 3	420
	21st to end	Day	27% 23% 30% 15% 5% 1	462
November	1st to 10th	Day	30% 21% 26% 16% 5% 2	425
	11th to 20th	Day	35% 19% 26% 16% 4 1	430
	21st to end	Day	31% 23% 28% 14% 4	430
December	1st to 10th	Day	31% 22% 30% 14% 3 1	430
	11th to 20th	Day	36% 23% 26% 12% 3	430
	21st to end	Day	25% 27% 29% 14% 4 1	473
January	1st to 10th	Night	25% 22% 31% 18% 4	950
	11th to 20th	Night	27% 21% 30% 17% 5%	950
	21st to end	Night	21% 22% 35% 18% 4	1031
February	1st to 10th	Night	28% 15% 32% 20% 4 1	840
	11th to 20th	Night	24% 25% 32% 15% 4	823
	21st to end	Night	18% 19% 37% 19% 7%	692
March	1st to 10th	Night	25% 18% 32% 20% 5%	840
	11th to 20th	Night	23% 14% 33% 22% 6% 1	840
	21st to end	Night	28% 17% 31% 19% 4 1	765
April	1st to 10th	Night	29% 18% 30% 20% 3	630
	11th to 20th	Night	26% 15% 30% 23% 5%	624
	21st to end	Night	32% 11% 30% 20% 7%	630
May	1st to 10th	Night	35% 10% 29% 17% 8% 2	630
	11th to 20th	Night	29% 7% 30% 24% 10%	622
	21st to end	Night	24% 10% 35% 24% 7%	682
June	1st to 10th	Night	35% 9% 26% 25% 5%	630
	11th to 20th	Night	25% 7% 35% 26% 7%	630
	21st to end	Night	29% 7% 32% 26% 6%	630
July	1st to 10th	Night	21% 6% 31% 32% 9%	616
	11th to 20th	Night	19% 6% 33% 34% 7%	612
	21st to end	Night	24% 6% 27% 35% 8%	689
August	1st to 10th	Night	19% 7% 25% 37% 13% 1	628
	11th to 20th	Night	21% 5% 24% 37% 12% 1	622
	21st to end	Night	17% 7% 24% 40% 11%	693
September	1st to 10th	Night	20% 7% 29% 32% 10% 2	630
	11th to 20th	Night	24% 11% 25% 30% 10% 1	610
	21st to end	Night	22% 10% 34% 26% 7%	635
October	1st to 10th	Night	23% 9% 30% 29% 9%	800
	11th to 20th	Night	25% 9% 30% 26% 9% 2	800
	21st to end	Night	30% 15% 30% 18% 5% 1	990
November	1st to 10th	Night	30% 16% 29% 20% 5% 1	930
	11th to 20th	Night	33% 17% 29% 15% 5% 1	950
	21st to end	Night	31% 19% 29% 18% 4	950
December	1st to 10th	Night	30% 20% 29% 17% 5%	950
	11th to 20th	Night	34% 22% 28% 13% 3	950
	21st to end	Night	27% 22% 32% 16% 3 1	1045

Page generated at 2026-09-11 05:11:54. Version ac07

Copyright © 2026 Attilla Danko.