Marten River Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marten River Provincial Park clear sky chart from 2005-11-06 to 2025-11-18.

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	17% 12% 4 9% 5% 4 4 3 5% 7% 30%	127239
	Night	16% 14% 5% 10% 5% 4 4 3 5% 6% 28%	123185
Transparency	Day	55% 3 11% 21% 9% 1	130769
	Night	58% 3 10% 19% 9% 1	127743
Seeing	Day	24% 14% 32% 21% 8% 2	16493
	Night	25% 12% 30% 25% 8% 1	25481

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% 9% 16% 7% 7% 4 3 4 5% 14%	3158
	11th to 20th	Day	11% 18% 9% 16% 7% 6% 3 3 4 6% 17%	3215
	21st to end	Day	12% 19% 8% 14% 6% 5% 4 3 5% 5% 18%	4466
February	1st to 10th	Day	9% 20% 6% 12% 9% 8% 4 3 4 4 20%	1800
	11th to 20th	Day	11% 19% 6% 12% 8% 4 4 3 4 5% 24%	1753
	21st to end	Day	15% 17% 5% 12% 6% 6% 5% 3 4 5% 22%	1495
March	1st to 10th	Day	19% 16% 4 10% 5% 4 4 3 5% 5% 25%	4877
	11th to 20th	Day	15% 14% 5% 12% 6% 5% 5% 3 5% 7% 24%	4980
	21st to end	Day	14% 16% 6% 11% 5% 5% 4 2 4 4 29%	5465
April	1st to 10th	Day	20% 14% 3 8% 5% 4 4 3 4 7% 27%	2370
	11th to 20th	Day	22% 11% 4 7% 5% 3 4 3 4 5% 33%	2540
	21st to end	Day	22% 12% 3 7% 4 4 3 2 4 5% 34%	2600
May	1st to 10th	Day	20% 10% 3 7% 5% 4 4 3 4 6% 34%	6090
	11th to 20th	Day	14% 8% 3 7% 5% 5% 4 3 6% 7% 39%	6318
	21st to end	Day	22% 9% 3 7% 4 4 3 3 4 7% 35%	6949
June	1st to 10th	Day	18% 10% 3 7% 5% 4 5% 4 5% 7% 33%	2999
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 5% 6% 7% 37%	3000
	21st to end	Day	18% 8% 3 8% 5% 5% 6% 4 6% 7% 31%	3000
July	1st to 10th	Day	16% 7% 3 7% 6% 5% 5% 4 7% 9% 32%	6819
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 9% 41%	6820
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 10% 43%	6856
August	1st to 10th	Day	12% 7% 3 6% 5% 5% 5% 5% 6% 10% 36%	4234
	11th to 20th	Day	19% 6% 2 6% 4 4 4 4 5% 8% 37%	4174
	21st to end	Day	12% 7% 3 7% 5% 5% 4 4 6% 8% 40%	4591
September	1st to 10th	Day	18% 7% 3 7% 4 4 5% 4 5% 7% 37%	2400
	11th to 20th	Day	18% 6% 2 6% 4 3 4 4 5% 8% 39%	2281
	21st to end	Day	22% 8% 3 7% 4 4 4 3 5% 6% 34%	2163
October	1st to 10th	Day	19% 11% 3 7% 4 5% 5% 3 5% 7% 33%	2000
	11th to 20th	Day	24% 15% 4 8% 5% 4 4 3 4 5% 24%	2000
	21st to end	Day	28% 17% 3 8% 5% 3 4 2 4 5% 19%	2140
November	1st to 10th	Day	20% 15% 4 9% 5% 4 4 4 4 6% 26%	1654
	11th to 20th	Day	18% 18% 6% 11% 6% 5% 5% 3 3 6% 18%	1656
	21st to end	Day	25% 22% 4 11% 6% 4 4 2 4 4 14%	1600
December	1st to 10th	Day	15% 23% 9% 16% 7% 5% 5% 3 4 4 10%	2600
	11th to 20th	Day	18% 20% 5% 14% 6% 3 3 2 4 4 22%	2700
	21st to end	Day	21% 20% 9% 17% 6% 4 2 2 4 4 12%	3476
January	1st to 10th	Night	12% 18% 8% 16% 9% 6% 4 3 5% 5% 14%	6808
	11th to 20th	Night	11% 17% 7% 15% 7% 6% 5% 4 4 4 19%	6682
	21st to end	Night	10% 20% 8% 15% 7% 5% 5% 3 5% 5% 18%	6490
February	1st to 10th	Night	10% 16% 6% 13% 8% 6% 6% 3 5% 5% 22%	2600
	11th to 20th	Night	12% 18% 7% 12% 7% 6% 4 3 4 4 22%	2533
	21st to end	Night	13% 19% 5% 10% 7% 6% 4 3 5% 5% 23%	2130
March	1st to 10th	Night	16% 17% 4 10% 5% 4 4 3 4 6% 27%	4962
	11th to 20th	Night	15% 15% 6% 10% 6% 5% 5% 4 5% 6% 24%	4979
	21st to end	Night	17% 12% 6% 9% 5% 4 4 3 4 5% 30%	5467
April	1st to 10th	Night	20% 15% 5% 8% 4 4 3 3 5% 5% 30%	2030
	11th to 20th	Night	19% 10% 4 8% 5% 4 4 4 4 6% 34%	1827
	21st to end	Night	21% 10% 3 7% 5% 4 5% 4 5% 6% 32%	1800
May	1st to 10th	Night	17% 10% 3 8% 4 4 3 3 5% 5% 36%	3851
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 3 5% 8% 42%	3575
	21st to end	Night	16% 10% 3 6% 4 4 4 4 5% 7% 37%	3911
June	1st to 10th	Night	16% 8% 3 7% 5% 5% 4 4 5% 6% 37%	1400
	11th to 20th	Night	15% 7% 2 6% 4 4 3 3 5% 8% 43%	1400
	21st to end	Night	15% 7% 3 7% 6% 4 5% 4 5% 8% 36%	1400
July	1st to 10th	Night	16% 8% 3 7% 5% 4 4 4 6% 7% 36%	3160
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 6% 8% 44%	3160
	21st to end	Night	11% 7% 2 6% 3 3 3 3 5% 8% 49%	3979
August	1st to 10th	Night	13% 4 2 6% 5% 4 5% 5% 6% 8% 42%	2915
	11th to 20th	Night	14% 8% 3 6% 4 3 4 3 5% 7% 42%	2875
	21st to end	Night	15% 6% 2 6% 3 3 4 3 4 7% 46%	3274
September	1st to 10th	Night	16% 6% 2 5% 4 4 4 4 5% 7% 45%	2000
	11th to 20th	Night	15% 8% 2 5% 2 3 3 3 4 6% 49%	2115
	21st to end	Night	18% 8% 2 6% 4 3 3 3 5% 7% 41%	2236
October	1st to 10th	Night	19% 9% 2 7% 4 4 4 3 5% 6% 36%	2400
	11th to 20th	Night	27% 13% 3 7% 4 4 4 3 4 6% 27%	2400
	21st to end	Night	25% 15% 4 8% 4 4 4 2 4 5% 24%	2696
November	1st to 10th	Night	20% 12% 3 8% 4 4 5% 3 5% 6% 28%	2862
	11th to 20th	Night	18% 18% 5% 10% 6% 5% 3 3 4 6% 21%	2899
	21st to end	Night	23% 19% 4 11% 7% 4 4 3 5% 4 17%	2800
December	1st to 10th	Night	16% 22% 6% 14% 7% 6% 4 3 4 5% 12%	4580
	11th to 20th	Night	16% 20% 5% 12% 6% 5% 4 3 5% 6% 18%	5487
	21st to end	Night	20% 22% 8% 15% 6% 3 3 3 3 3 15%	7502

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	76% 2 10% 9% 3	3159
	11th to 20th	Day	71% 2 8% 10% 9%	3242
	21st to end	Day	69% 2 7% 14% 8%	4466
February	1st to 10th	Day	68% 3 7% 14% 7% 1	1800
	11th to 20th	Day	65% 2 8% 13% 10% 1	1762
	21st to end	Day	66% 2 5% 17% 10% 1	1495
March	1st to 10th	Day	63% 2 8% 13% 13% 2	4880
	11th to 20th	Day	62% 3 11% 14% 9% 1	4980
	21st to end	Day	61% 1 8% 18% 11% 2	5465
April	1st to 10th	Day	58% 3 9% 20% 9% 1	2370
	11th to 20th	Day	56% 2 5% 23% 13% 1	2540
	21st to end	Day	55% 2 7% 19% 15% 3	2600
May	1st to 10th	Day	53% 2 6% 21% 15% 4	6099
	11th to 20th	Day	46% 3 11% 25% 13% 2	6322
	21st to end	Day	51% 3 10% 21% 13% 1	6949
June	1st to 10th	Day	52% 3 10% 23% 12% 1	2999
	11th to 20th	Day	45% 4 11% 26% 14% 1	3000
	21st to end	Day	52% 4 12% 21% 10% 1	3000
July	1st to 10th	Day	47% 7% 15% 26% 6%	6746
	11th to 20th	Day	38% 5% 19% 32% 5%	6739
	21st to end	Day	36% 5% 17% 32% 9%	6659
August	1st to 10th	Day	42% 5% 15% 31% 7%	4221
	11th to 20th	Day	45% 4 16% 26% 8% 1	4213
	21st to end	Day	41% 4 13% 33% 8% 1	4591
September	1st to 10th	Day	48% 3 14% 25% 10% 1	2400
	11th to 20th	Day	44% 4 14% 28% 10%	2281
	21st to end	Day	53% 4 12% 24% 8%	2163
October	1st to 10th	Day	49% 4 12% 28% 6%	3260
	11th to 20th	Day	55% 4 11% 21% 8%	3240
	21st to end	Day	67% 4 14% 10% 5%	3442
November	1st to 10th	Day	61% 3 13% 17% 6%	1654
	11th to 20th	Day	68% 3 10% 13% 5% 1	1656
	21st to end	Day	76% 3 8% 9% 4	1600
December	1st to 10th	Day	80% 3 8% 7% 2	2600
	11th to 20th	Day	68% 2 7% 18% 5%	2700
	21st to end	Day	78% 1 5% 12% 4	3476
January	1st to 10th	Night	73% 2 9% 11% 4	6808
	11th to 20th	Night	70% 2 9% 11% 7%	6730
	21st to end	Night	70% 2 5% 11% 11% 1	6490
February	1st to 10th	Night	65% 3 8% 16% 7% 1	2600
	11th to 20th	Night	67% 2 8% 16% 6% 1	2535
	21st to end	Night	64% 3 7% 17% 9% 1	2130
March	1st to 10th	Night	60% 2 7% 14% 12% 4	4972
	11th to 20th	Night	62% 3 11% 16% 7% 1	4980
	21st to end	Night	58% 2 6% 19% 12% 3	5467
April	1st to 10th	Night	59% 2 8% 18% 12% 2	2030
	11th to 20th	Night	54% 2 5% 22% 16% 2	1827
	21st to end	Night	53% 3 11% 15% 16% 3	1800
May	1st to 10th	Night	51% 2 5% 21% 19% 3	3858
	11th to 20th	Night	42% 3 11% 23% 17% 3	3576
	21st to end	Night	47% 3 11% 22% 14% 3	3912
June	1st to 10th	Night	49% 3 10% 25% 11% 3	1400
	11th to 20th	Night	40% 4 12% 26% 17% 2	1400
	21st to end	Night	47% 5% 13% 21% 14% 1	1400
July	1st to 10th	Night	46% 5% 11% 28% 9% 1	3125
	11th to 20th	Night	38% 5% 16% 31% 8%	3118
	21st to end	Night	34% 4 14% 33% 14%	3862
August	1st to 10th	Night	39% 6% 16% 29% 9%	2904
	11th to 20th	Night	41% 6% 17% 28% 8%	2902
	21st to end	Night	38% 4 16% 29% 11% 1	3274
September	1st to 10th	Night	39% 5% 16% 29% 10% 2	2000
	11th to 20th	Night	38% 3 15% 33% 11%	2115
	21st to end	Night	45% 3 15% 28% 9%	2236
October	1st to 10th	Night	46% 5% 13% 26% 10%	3920
	11th to 20th	Night	53% 4 13% 26% 5%	3899
	21st to end	Night	57% 6% 17% 14% 5%	4344
November	1st to 10th	Night	57% 3 14% 19% 6%	2862
	11th to 20th	Night	67% 3 10% 15% 6% 1	2899
	21st to end	Night	71% 3 11% 12% 4	2800
December	1st to 10th	Night	76% 4 8% 10% 2	4580
	11th to 20th	Night	69% 2 7% 12% 9%	5486
	21st to end	Night	76% 2 5% 12% 4	7502

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	26% 16% 37% 18% 4 1	200
	11th to 20th	Day	23% 11% 41% 17% 8%	211
	21st to end	Day	26% 10% 37% 20% 6% 1	330
February	1st to 10th	Day	32% 26% 29% 9% 3	300
	11th to 20th	Day	24% 24% 38% 13% 1	300
	21st to end	Day	34% 21% 35% 9%	249
March	1st to 10th	Day	24% 20% 35% 17% 4	469
	11th to 20th	Day	23% 18% 37% 18% 3 1	500
	21st to end	Day	28% 19% 32% 16% 4 1	550
April	1st to 10th	Day	28% 20% 28% 17% 6% 2	500
	11th to 20th	Day	37% 15% 24% 15% 7% 2	492
	21st to end	Day	34% 16% 31% 12% 5% 2	500
May	1st to 10th	Day	26% 11% 32% 19% 11% 1	503
	11th to 20th	Day	22% 15% 31% 22% 8% 2	527
	21st to end	Day	25% 12% 31% 22% 8% 2	573
June	1st to 10th	Day	21% 15% 35% 22% 5% 2	729
	11th to 20th	Day	17% 16% 33% 24% 8% 2	730
	21st to end	Day	22% 12% 32% 23% 9% 2	730
July	1st to 10th	Day	15% 10% 34% 30% 9% 2	721
	11th to 20th	Day	17% 9% 31% 27% 13% 3	718
	21st to end	Day	15% 8% 32% 30% 11% 4	603
August	1st to 10th	Day	19% 6% 29% 28% 14% 4	526
	11th to 20th	Day	18% 5% 27% 27% 15% 9%	519
	21st to end	Day	20% 10% 28% 23% 14% 4	583
September	1st to 10th	Day	24% 11% 30% 22% 9% 3	530
	11th to 20th	Day	18% 6% 28% 30% 11% 7%	530
	21st to end	Day	28% 9% 24% 23% 12% 4	530
October	1st to 10th	Day	27% 14% 27% 19% 11% 2	530
	11th to 20th	Day	31% 17% 35% 12% 3 1	530
	21st to end	Day	33% 15% 35% 14% 3	523
November	1st to 10th	Day	37% 16% 33% 13% 1 1	223
	11th to 20th	Day	26% 21% 33% 15% 3 1	214
	21st to end	Day	39% 17% 27% 15% 2 1	200
December	1st to 10th	Day	31% 15% 34% 19% 3	200
	11th to 20th	Day	31% 17% 34% 15% 5% 1	200
	21st to end	Day	34% 15% 32% 15% 5%	220
January	1st to 10th	Night	26% 13% 34% 21% 6%	1000
	11th to 20th	Night	30% 13% 29% 22% 5%	987
	21st to end	Night	21% 12% 32% 24% 9% 1	880
February	1st to 10th	Night	18% 18% 37% 22% 4 1	800
	11th to 20th	Night	23% 15% 38% 19% 4	783
	21st to end	Night	23% 18% 35% 20% 4	660
March	1st to 10th	Night	22% 19% 34% 20% 5%	800
	11th to 20th	Night	25% 15% 36% 18% 6% 1	800
	21st to end	Night	21% 15% 34% 24% 6% 1	880
April	1st to 10th	Night	28% 14% 30% 23% 5%	800
	11th to 20th	Night	27% 15% 29% 21% 8% 1	643
	21st to end	Night	28% 11% 29% 23% 8% 1	600
May	1st to 10th	Night	21% 9% 30% 31% 8% 1	515
	11th to 20th	Night	22% 8% 32% 27% 10% 1	394
	21st to end	Night	20% 9% 33% 31% 6%	433
June	1st to 10th	Night	21% 6% 31% 33% 10%	400
	11th to 20th	Night	20% 9% 28% 32% 11% 1	400
	21st to end	Night	21% 8% 26% 30% 14% 1	400
July	1st to 10th	Night	12% 6% 31% 40% 10% 1	390
	11th to 20th	Night	13% 7% 28% 37% 15% 1	388
	21st to end	Night	12% 5% 28% 39% 16% 1	483
August	1st to 10th	Night	15% 3 25% 39% 18% 1	597
	11th to 20th	Night	17% 5% 24% 31% 21% 3	594
	21st to end	Night	20% 7% 25% 30% 15% 2	685
September	1st to 10th	Night	20% 7% 28% 28% 17% 1	800
	11th to 20th	Night	19% 7% 25% 29% 17% 3	800
	21st to end	Night	23% 6% 26% 29% 14% 2	800
October	1st to 10th	Night	24% 11% 27% 29% 8% 1	800
	11th to 20th	Night	35% 10% 27% 20% 7% 1	800
	21st to end	Night	35% 12% 25% 23% 5% 1	880
November	1st to 10th	Night	30% 12% 31% 22% 5% 1	820
	11th to 20th	Night	30% 15% 29% 20% 7%	829
	21st to end	Night	34% 13% 28% 20% 5% 1	800
December	1st to 10th	Night	33% 14% 31% 16% 5% 1	800
	11th to 20th	Night	29% 14% 33% 18% 6% 1	940
	21st to end	Night	31% 14% 29% 20% 5% 1	1100

Page generated at 2025-11-15 00:55:59. Version ac07

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