Gatineau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gatineau clear sky chart from 2005-11-06 to 2026-03-18.

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	16% 10% 3 8% 5% 5% 5% 4 5% 7% 31%	131404
	Night	16% 11% 4 9% 5% 5% 5% 4 5% 6% 30%	130075
Transparency	Day	50% 7% 12% 20% 9% 1	134869
	Night	53% 7% 11% 18% 10% 1	134697
Seeing	Day	21% 15% 29% 22% 10% 3	16085
	Night	22% 12% 29% 27% 10% 1	25303

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	14% 16% 7% 15% 6% 5% 5% 4 5% 6% 19%	4661
	11th to 20th	Day	11% 18% 7% 15% 7% 5% 4 3 4 6% 19%	4650
	21st to end	Day	8% 14% 6% 15% 8% 8% 5% 4 6% 5% 20%	5322
February	1st to 10th	Day	12% 14% 5% 13% 7% 6% 4 4 5% 5% 25%	1890
	11th to 20th	Day	13% 15% 5% 10% 6% 5% 4 4 6% 5% 27%	1852
	21st to end	Day	18% 13% 4 11% 7% 6% 5% 4 5% 5% 24%	1730
March	1st to 10th	Day	19% 12% 4 11% 6% 5% 5% 4 5% 5% 24%	4576
	11th to 20th	Day	13% 11% 4 9% 5% 5% 5% 4 6% 7% 30%	5046
	21st to end	Day	17% 11% 4 8% 6% 4 3 3 4 5% 36%	5781
April	1st to 10th	Day	22% 10% 3 7% 5% 4 5% 2 5% 6% 33%	2400
	11th to 20th	Day	21% 9% 3 7% 4 3 4 3 4 5% 36%	2374
	21st to end	Day	22% 9% 3 8% 6% 5% 4 3 4 5% 31%	2545
May	1st to 10th	Day	23% 10% 3 8% 5% 5% 5% 4 6% 6% 26%	6346
	11th to 20th	Day	17% 9% 3 8% 6% 5% 5% 4 5% 6% 31%	6318
	21st to end	Day	21% 8% 3 7% 5% 5% 4 4 5% 6% 33%	6949
June	1st to 10th	Day	21% 8% 2 7% 6% 4 4 4 6% 6% 30%	2800
	11th to 20th	Day	13% 6% 2 7% 5% 4 6% 4 6% 8% 39%	2800
	21st to end	Day	20% 6% 3 6% 5% 5% 6% 5% 6% 7% 32%	2800
July	1st to 10th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 9% 34%	6360
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 4 6% 8% 43%	6360
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 11% 46%	6926
August	1st to 10th	Day	13% 5% 3 8% 5% 5% 5% 4 7% 8% 37%	4508
	11th to 20th	Day	16% 6% 2 6% 4 4 4 4 7% 9% 38%	4117
	21st to end	Day	14% 5% 2 6% 4 5% 5% 4 6% 9% 40%	4312
September	1st to 10th	Day	13% 5% 2 6% 4 4 5% 4 5% 8% 43%	2400
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 7% 49%	2396
	21st to end	Day	19% 5% 3 5% 4 4 4 4 5% 8% 40%	2140
October	1st to 10th	Day	19% 8% 3 6% 4 4 3 4 6% 6% 37%	2000
	11th to 20th	Day	22% 8% 3 7% 6% 5% 6% 4 5% 6% 29%	2000
	21st to end	Day	25% 10% 3 7% 5% 5% 5% 3 4 6% 29%	2030
November	1st to 10th	Day	15% 10% 3 8% 5% 5% 5% 4 6% 6% 33%	1851
	11th to 20th	Day	19% 11% 4 9% 5% 5% 6% 4 6% 6% 26%	1690
	21st to end	Day	22% 15% 4 9% 6% 5% 5% 4 5% 6% 20%	1680
December	1st to 10th	Day	20% 19% 6% 9% 5% 4 5% 4 6% 5% 14%	2680
	11th to 20th	Day	17% 15% 4 11% 7% 5% 4 3 4 4 26%	3066
	21st to end	Day	23% 16% 4 10% 6% 5% 5% 3 4 5% 19%	4048
January	1st to 10th	Night	13% 19% 8% 15% 5% 5% 4 3 4 4 20%	8234
	11th to 20th	Night	11% 18% 6% 15% 8% 6% 5% 3 4 5% 18%	8235
	21st to end	Night	10% 17% 5% 12% 7% 6% 6% 4 5% 6% 22%	8840
February	1st to 10th	Night	13% 14% 5% 12% 6% 6% 5% 4 5% 5% 25%	2730
	11th to 20th	Night	13% 13% 5% 12% 7% 6% 4 3 4 6% 28%	2653
	21st to end	Night	16% 13% 5% 9% 6% 4 5% 4 5% 6% 28%	2076
March	1st to 10th	Night	22% 14% 4 9% 5% 4 4 3 3 4 28%	5484
	11th to 20th	Night	13% 12% 4 9% 6% 5% 5% 4 6% 8% 29%	5062
	21st to end	Night	19% 9% 3 8% 5% 5% 3 3 5% 6% 34%	5151
April	1st to 10th	Night	20% 11% 3 8% 5% 3 4 3 5% 6% 32%	2000
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 5% 36%	1975
	21st to end	Night	22% 8% 3 6% 4 4 4 3 5% 6% 34%	1870
May	1st to 10th	Night	22% 9% 3 9% 5% 5% 5% 4 7% 7% 24%	3594
	11th to 20th	Night	17% 7% 3 7% 5% 4 4 3 5% 7% 37%	3575
	21st to end	Night	19% 8% 4 8% 5% 5% 4 5% 5% 6% 31%	3926
June	1st to 10th	Night	16% 6% 3 6% 6% 6% 5% 4 7% 8% 34%	1600
	11th to 20th	Night	14% 6% 3 6% 4 4 4 5% 6% 7% 42%	1600
	21st to end	Night	18% 7% 3 6% 4 5% 4 4 7% 7% 35%	1600
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 6% 5% 7% 8% 33%	3600
	11th to 20th	Night	11% 6% 2 7% 4 4 4 4 6% 7% 43%	3600
	21st to end	Night	9% 5% 2 6% 5% 5% 4 4 6% 7% 47%	3926
August	1st to 10th	Night	12% 6% 3 7% 4 5% 5% 5% 6% 8% 39%	2637
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 6% 7% 42%	2898
	21st to end	Night	13% 5% 3 6% 5% 5% 5% 4 6% 7% 40%	3586
September	1st to 10th	Night	12% 4 2 6% 4 4 4 4 5% 6% 48%	2000
	11th to 20th	Night	14% 4 2 5% 3 4 3 3 5% 6% 50%	2003
	21st to end	Night	18% 5% 2 7% 5% 3 4 3 4 5% 44%	2257
October	1st to 10th	Night	18% 7% 2 5% 4 4 5% 3 5% 6% 41%	2400
	11th to 20th	Night	20% 7% 3 7% 7% 5% 5% 3 5% 6% 32%	2400
	21st to end	Night	22% 9% 3 8% 5% 5% 5% 3 4 7% 29%	2809
November	1st to 10th	Night	20% 9% 3 6% 5% 5% 4 3 5% 6% 33%	2667
	11th to 20th	Night	18% 11% 4 9% 5% 5% 5% 4 5% 6% 30%	2929
	21st to end	Night	21% 12% 4 9% 6% 5% 4 4 4 6% 24%	2940
December	1st to 10th	Night	18% 17% 5% 10% 6% 6% 5% 4 5% 6% 17%	4720
	11th to 20th	Night	23% 14% 4 9% 6% 4 4 3 4 5% 26%	5348
	21st to end	Night	26% 18% 4 9% 4 4 4 3 4 4 20%	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	65% 7% 10% 14% 4	4662
	11th to 20th	Day	65% 5% 9% 11% 9%	4680
	21st to end	Day	62% 8% 12% 10% 8% 1	5322
February	1st to 10th	Day	60% 5% 11% 18% 6% 1	1890
	11th to 20th	Day	58% 5% 12% 16% 8% 1	1861
	21st to end	Day	60% 6% 10% 13% 9% 2	1730
March	1st to 10th	Day	59% 6% 10% 13% 10% 3	4579
	11th to 20th	Day	51% 8% 17% 14% 9% 1	5046
	21st to end	Day	50% 6% 6% 19% 17% 2	5781
April	1st to 10th	Day	53% 5% 8% 19% 12% 3	2400
	11th to 20th	Day	50% 4 7% 22% 14% 2	2374
	21st to end	Day	55% 5% 8% 15% 13% 4	2545
May	1st to 10th	Day	56% 7% 8% 19% 8% 2	6357
	11th to 20th	Day	50% 8% 13% 18% 10% 1	6322
	21st to end	Day	50% 7% 11% 19% 12% 1	6949
June	1st to 10th	Day	52% 7% 11% 18% 12% 1	2800
	11th to 20th	Day	42% 8% 11% 24% 12% 2	2800
	21st to end	Day	47% 9% 13% 20% 10% 1	2800
July	1st to 10th	Day	42% 9% 15% 25% 9%	6290
	11th to 20th	Day	36% 8% 14% 30% 13%	6285
	21st to end	Day	31% 8% 16% 35% 10%	6728
August	1st to 10th	Day	43% 8% 16% 24% 9%	4494
	11th to 20th	Day	40% 8% 16% 28% 7% 1	4156
	21st to end	Day	38% 7% 17% 26% 11% 1	4312
September	1st to 10th	Day	37% 8% 15% 29% 11%	2400
	11th to 20th	Day	34% 7% 14% 32% 13% 1	2396
	21st to end	Day	43% 7% 14% 25% 10%	2140
October	1st to 10th	Day	45% 7% 13% 28% 7%	3260
	11th to 20th	Day	45% 7% 16% 24% 8% 1	3240
	21st to end	Day	48% 7% 18% 20% 7%	3255
November	1st to 10th	Day	48% 7% 14% 22% 7% 1	1851
	11th to 20th	Day	56% 7% 13% 16% 8% 1	1690
	21st to end	Day	65% 7% 12% 9% 6% 1	1680
December	1st to 10th	Day	67% 8% 13% 9% 2	2680
	11th to 20th	Day	62% 5% 10% 15% 7%	3066
	21st to end	Day	67% 6% 8% 15% 4	4048
January	1st to 10th	Night	67% 5% 11% 12% 5%	8234
	11th to 20th	Night	67% 6% 10% 11% 6%	8280
	21st to end	Night	61% 6% 9% 12% 11% 1	8840
February	1st to 10th	Night	60% 6% 11% 17% 7% 1	2730
	11th to 20th	Night	58% 5% 10% 20% 7% 1	2655
	21st to end	Night	56% 6% 9% 18% 10% 1	2076
March	1st to 10th	Night	60% 5% 7% 14% 11% 3	5494
	11th to 20th	Night	52% 7% 16% 15% 8% 3	5063
	21st to end	Night	50% 6% 7% 22% 13% 2	5151
April	1st to 10th	Night	53% 5% 9% 17% 13% 2	2000
	11th to 20th	Night	49% 6% 8% 20% 16% 1	1975
	21st to end	Night	51% 5% 9% 18% 15% 3	1870
May	1st to 10th	Night	55% 9% 9% 18% 7% 3	3600
	11th to 20th	Night	44% 8% 14% 19% 14% 1	3576
	21st to end	Night	50% 7% 11% 16% 14% 1	3927
June	1st to 10th	Night	46% 7% 12% 23% 10% 1	1600
	11th to 20th	Night	39% 8% 11% 23% 16% 2	1600
	21st to end	Night	46% 9% 12% 19% 14% 1	1600
July	1st to 10th	Night	44% 9% 16% 20% 11% 1	3560
	11th to 20th	Night	36% 9% 14% 31% 11%	3552
	21st to end	Night	34% 8% 13% 30% 16%	3809
August	1st to 10th	Night	40% 9% 16% 24% 10% 1	2627
	11th to 20th	Night	39% 9% 15% 30% 8%	2925
	21st to end	Night	39% 9% 16% 23% 12% 2	3586
September	1st to 10th	Night	36% 7% 12% 30% 14% 1	2000
	11th to 20th	Night	33% 8% 13% 34% 11% 1	2003
	21st to end	Night	42% 5% 12% 29% 12%	2257
October	1st to 10th	Night	38% 7% 15% 27% 12% 1	3920
	11th to 20th	Night	43% 7% 15% 25% 9%	3899
	21st to end	Night	46% 7% 18% 20% 9%	4534
November	1st to 10th	Night	51% 7% 14% 20% 8%	2667
	11th to 20th	Night	56% 5% 12% 17% 9% 1	2929
	21st to end	Night	61% 7% 13% 15% 5%	2940
December	1st to 10th	Night	66% 7% 12% 12% 3	4720
	11th to 20th	Night	62% 5% 8% 14% 10% 1	5348
	21st to end	Night	68% 5% 7% 12% 9%	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	22% 17% 34% 23% 4	220
	11th to 20th	Day	26% 16% 38% 15% 4 1	220
	21st to end	Day	19% 16% 38% 22% 6%	278
February	1st to 10th	Day	28% 20% 34% 15% 3	330
	11th to 20th	Day	25% 25% 34% 14% 1	339
	21st to end	Day	28% 18% 32% 19% 3	446
March	1st to 10th	Day	25% 18% 34% 18% 5%	540
	11th to 20th	Day	26% 18% 31% 20% 3 1	528
	21st to end	Day	28% 21% 28% 15% 8% 1	550
April	1st to 10th	Day	27% 22% 29% 15% 6%	500
	11th to 20th	Day	31% 19% 24% 15% 10% 1	492
	21st to end	Day	29% 18% 31% 13% 6% 2	500
May	1st to 10th	Day	24% 14% 32% 21% 7% 2	503
	11th to 20th	Day	18% 17% 31% 20% 11% 2	527
	21st to end	Day	20% 15% 29% 24% 11% 2	573
June	1st to 10th	Day	24% 12% 28% 24% 10% 2	530
	11th to 20th	Day	16% 15% 29% 26% 12% 2	530
	21st to end	Day	22% 12% 29% 24% 11% 2	530
July	1st to 10th	Day	12% 9% 27% 34% 13% 5%	525
	11th to 20th	Day	12% 8% 33% 28% 15% 3	524
	21st to end	Day	12% 8% 31% 30% 15% 4	576
August	1st to 10th	Day	13% 6% 25% 33% 17% 4	526
	11th to 20th	Day	14% 8% 22% 29% 19% 8%	519
	21st to end	Day	14% 11% 28% 25% 15% 7%	583
September	1st to 10th	Day	16% 9% 29% 22% 14% 9%	530
	11th to 20th	Day	11% 8% 21% 25% 22% 13%	530
	21st to end	Day	18% 12% 28% 24% 13% 5%	530
October	1st to 10th	Day	22% 12% 26% 23% 12% 5%	530
	11th to 20th	Day	23% 18% 32% 18% 8% 1	530
	21st to end	Day	31% 12% 28% 22% 6%	489
November	1st to 10th	Day	26% 17% 29% 19% 8% 1	425
	11th to 20th	Day	24% 18% 36% 15% 6% 1	230
	21st to end	Day	31% 18% 30% 15% 4 1	220
December	1st to 10th	Day	27% 15% 33% 21% 4	220
	11th to 20th	Day	25% 23% 34% 16% 2	220
	21st to end	Day	32% 19% 30% 15% 3 1	242
January	1st to 10th	Night	26% 13% 35% 22% 4	840
	11th to 20th	Night	26% 16% 29% 23% 6% 1	840
	21st to end	Night	19% 10% 36% 27% 6%	924
February	1st to 10th	Night	22% 13% 33% 28% 4	840
	11th to 20th	Night	19% 17% 37% 23% 4	823
	21st to end	Night	23% 15% 29% 29% 4	692
March	1st to 10th	Night	24% 15% 34% 23% 4	840
	11th to 20th	Night	24% 17% 32% 23% 4	829
	21st to end	Night	24% 15% 29% 24% 8%	880
April	1st to 10th	Night	27% 14% 30% 24% 5%	800
	11th to 20th	Night	23% 15% 31% 22% 8%	791
	21st to end	Night	26% 12% 28% 25% 8% 1	670
May	1st to 10th	Night	24% 8% 28% 30% 9% 2	400
	11th to 20th	Night	20% 11% 25% 33% 10% 1	394
	21st to end	Night	15% 8% 37% 30% 10%	433
June	1st to 10th	Night	18% 4 30% 39% 9%	400
	11th to 20th	Night	15% 7% 29% 35% 13% 2	400
	21st to end	Night	20% 7% 27% 31% 14% 1	400
July	1st to 10th	Night	9% 4 28% 42% 16%	390
	11th to 20th	Night	12% 5% 21% 45% 17% 1	388
	21st to end	Night	8% 4 27% 42% 17% 1	438
August	1st to 10th	Night	11% 4 21% 39% 24%	423
	11th to 20th	Night	13% 4 18% 38% 25% 3	604
	21st to end	Night	13% 8% 21% 36% 20% 2	880
September	1st to 10th	Night	13% 6% 27% 33% 20% 1	800
	11th to 20th	Night	16% 5% 20% 32% 24% 4	800
	21st to end	Night	20% 8% 25% 26% 20% 2	800
October	1st to 10th	Night	21% 8% 26% 26% 17% 2	800
	11th to 20th	Night	24% 11% 30% 26% 9% 1	800
	21st to end	Night	27% 13% 26% 28% 6%	880
November	1st to 10th	Night	25% 14% 25% 27% 8% 1	820
	11th to 20th	Night	24% 15% 35% 17% 9% 1	840
	21st to end	Night	28% 17% 27% 22% 6%	840
December	1st to 10th	Night	29% 15% 29% 24% 4	840
	11th to 20th	Night	27% 16% 31% 21% 5% 1	840
	21st to end	Night	33% 14% 30% 20% 4	924

Page generated at 2026-03-15 02:23:56. Version ac07

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