Driftwood Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Driftwood Provincial Park clear sky chart from 2005-11-06 to 2026-05-02.

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% 12% 4 9% 5% 5% 4 3 5% 6% 30%	132789
	Night	16% 13% 5% 11% 6% 5% 4 3 5% 6% 27%	129672
Transparency	Day	37% 36% 7% 14% 6% 1	136317
	Night	39% 36% 7% 12% 6% 1	134233
Seeing	Day	24% 15% 30% 20% 9% 2	16569
	Night	24% 12% 27% 26% 10% 1	25410

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% 17% 8% 16% 9% 5% 4 3 5% 5% 15%	4661
	11th to 20th	Day	10% 23% 8% 18% 7% 4 4 3 4 5% 15%	4650
	21st to end	Day	9% 15% 7% 17% 8% 7% 5% 4 4 5% 19%	5582
February	1st to 10th	Day	10% 16% 7% 15% 10% 6% 5% 4 4 5% 19%	1890
	11th to 20th	Day	11% 18% 6% 13% 6% 6% 5% 4 4 5% 22%	1843
	21st to end	Day	16% 16% 6% 11% 6% 5% 5% 4 4 4 22%	1620
March	1st to 10th	Day	20% 16% 5% 10% 4 4 4 3 4 5% 24%	4847
	11th to 20th	Day	14% 13% 4 11% 6% 5% 4 4 6% 7% 26%	5090
	21st to end	Day	16% 13% 4 10% 5% 5% 4 3 3 4 33%	5714
April	1st to 10th	Day	22% 13% 4 8% 5% 4 4 2 4 5% 28%	2520
	11th to 20th	Day	21% 12% 3 7% 4 5% 3 3 4 5% 33%	2532
	21st to end	Day	21% 12% 3 8% 5% 4 4 3 4 5% 33%	2730
May	1st to 10th	Day	20% 11% 3 8% 4 5% 4 3 5% 6% 31%	6303
	11th to 20th	Day	16% 8% 3 7% 5% 5% 4 3 6% 8% 36%	6318
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 4 6% 34%	6949
June	1st to 10th	Day	20% 9% 3 8% 5% 6% 4 4 5% 6% 31%	2800
	11th to 20th	Day	15% 5% 2 6% 6% 5% 6% 5% 5% 8% 38%	2914
	21st to end	Day	19% 7% 3 7% 6% 5% 5% 4 6% 7% 32%	3000
July	1st to 10th	Day	16% 7% 3 7% 6% 5% 5% 4 6% 8% 33%	6730
	11th to 20th	Day	12% 5% 2 7% 5% 4 5% 4 6% 8% 41%	6360
	21st to end	Day	9% 5% 2 5% 4 4 4 4 7% 10% 45%	6926
August	1st to 10th	Day	12% 7% 2 8% 5% 6% 6% 5% 7% 8% 33%	4318
	11th to 20th	Day	17% 6% 2 6% 5% 4 5% 4 6% 8% 36%	4174
	21st to end	Day	10% 6% 2 7% 5% 5% 6% 4 7% 9% 39%	4445
September	1st to 10th	Day	15% 7% 2 7% 5% 4 4 3 5% 7% 41%	2400
	11th to 20th	Day	14% 7% 3 7% 4 4 4 3 5% 7% 43%	2400
	21st to end	Day	21% 8% 3 6% 4 5% 3 3 5% 7% 34%	2087
October	1st to 10th	Day	19% 9% 3 8% 4 4 4 3 5% 7% 35%	2000
	11th to 20th	Day	24% 14% 3 9% 5% 5% 4 3 5% 5% 24%	2000
	21st to end	Day	27% 15% 4 9% 4 4 5% 3 4 4 21%	2121
November	1st to 10th	Day	18% 14% 5% 9% 4 4 4 3 5% 5% 28%	1711
	11th to 20th	Day	18% 18% 7% 12% 5% 5% 4 3 4 4 20%	1680
	21st to end	Day	26% 19% 7% 12% 5% 4 4 2 4 3 14%	1680
December	1st to 10th	Day	17% 22% 6% 13% 6% 5% 6% 4 4 4 12%	2680
	11th to 20th	Day	15% 21% 7% 14% 7% 4 3 2 2 4 20%	3066
	21st to end	Day	20% 21% 7% 16% 6% 4 4 2 2 4 15%	4048
January	1st to 10th	Night	12% 19% 9% 17% 8% 5% 4 3 4 4 13%	8234
	11th to 20th	Night	11% 17% 7% 18% 8% 6% 5% 4 5% 4 15%	8235
	21st to end	Night	7% 17% 8% 16% 8% 8% 6% 4 4 5% 17%	8581
February	1st to 10th	Night	12% 14% 6% 12% 8% 6% 5% 4 5% 5% 22%	2730
	11th to 20th	Night	13% 14% 6% 13% 7% 5% 5% 3 5% 5% 23%	2663
	21st to end	Night	14% 17% 5% 12% 7% 6% 4 4 5% 5% 21%	2184
March	1st to 10th	Night	17% 18% 4 9% 4 4 4 4 4 5% 26%	5210
	11th to 20th	Night	12% 15% 5% 10% 5% 5% 4 4 7% 7% 24%	5089
	21st to end	Night	17% 12% 5% 11% 5% 4 5% 3 5% 5% 29%	5459
April	1st to 10th	Night	21% 12% 4 8% 4 4 5% 3 5% 5% 29%	2100
	11th to 20th	Night	19% 10% 4 7% 5% 4 3 3 5% 5% 35%	2055
	21st to end	Night	23% 8% 3 7% 5% 4 4 4 5% 5% 31%	1890
May	1st to 10th	Night	22% 9% 2 7% 4 4 4 4 5% 7% 31%	3657
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 4 5% 7% 41%	3575
	21st to end	Night	18% 9% 3 9% 5% 5% 4 3 4 6% 35%	3926
June	1st to 10th	Night	17% 8% 3 8% 5% 5% 4 4 5% 7% 34%	1600
	11th to 20th	Night	16% 6% 2 5% 5% 4 4 4 6% 8% 40%	1479
	21st to end	Night	18% 6% 2 6% 5% 4 5% 4 6% 8% 35%	1400
July	1st to 10th	Night	15% 6% 3 8% 5% 5% 6% 4 6% 7% 34%	3239
	11th to 20th	Night	13% 7% 3 6% 5% 4 4 3 5% 7% 43%	3600
	21st to end	Night	10% 6% 2 6% 3 4 4 3 6% 8% 48%	3926
August	1st to 10th	Night	12% 5% 2 6% 4 4 5% 4 6% 8% 44%	2815
	11th to 20th	Night	16% 7% 2 6% 4 4 4 4 6% 7% 41%	2875
	21st to end	Night	14% 5% 1 6% 4 4 4 4 7% 8% 42%	3419
September	1st to 10th	Night	13% 6% 2 5% 3 4 4 4 5% 7% 46%	2000
	11th to 20th	Night	15% 6% 2 5% 4 3 4 3 4 6% 47%	2000
	21st to end	Night	20% 8% 2 6% 3 4 3 3 4 7% 39%	2310
October	1st to 10th	Night	19% 9% 3 6% 4 3 4 3 5% 6% 37%	2400
	11th to 20th	Night	24% 13% 3 8% 5% 4 4 3 4 6% 27%	2400
	21st to end	Night	27% 13% 3 8% 4 4 4 3 5% 5% 24%	2718
November	1st to 10th	Night	19% 14% 4 9% 5% 4 4 3 5% 5% 29%	2805
	11th to 20th	Night	19% 16% 5% 10% 6% 5% 4 3 4 5% 22%	2940
	21st to end	Night	25% 18% 5% 12% 6% 4 3 3 3 5% 15%	2940
December	1st to 10th	Night	18% 22% 6% 13% 7% 5% 5% 4 4 5% 11%	4720
	11th to 20th	Night	18% 18% 6% 14% 6% 5% 3 2 4 4 20%	5348
	21st to end	Night	23% 19% 5% 15% 6% 4 3 2 3 4 15%	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	60% 20% 6% 9% 4	4662
	11th to 20th	Day	61% 20% 5% 7% 6%	4680
	21st to end	Day	55% 23% 5% 10% 7%	5582
February	1st to 10th	Day	29% 59% 4 6% 3	1890
	11th to 20th	Day	28% 58% 3 7% 4	1852
	21st to end	Day	29% 58% 2 6% 5%	1620
March	1st to 10th	Day	48% 28% 5% 7% 10% 2	4850
	11th to 20th	Day	43% 28% 10% 11% 6% 1	5090
	21st to end	Day	43% 27% 4 16% 10% 1	5714
April	1st to 10th	Day	26% 59% 3 7% 5% 1	2520
	11th to 20th	Day	25% 59% 2 8% 5% 1	2532
	21st to end	Day	23% 58% 3 8% 6% 1	2730
May	1st to 10th	Day	41% 28% 4 17% 5% 4	6314
	11th to 20th	Day	33% 29% 9% 20% 8% 1	6322
	21st to end	Day	41% 28% 7% 14% 9% 1	6949
June	1st to 10th	Day	21% 62% 3 10% 5% 1	2800
	11th to 20th	Day	19% 62% 4 8% 6% 1	2914
	21st to end	Day	20% 61% 5% 9% 5%	3000
July	1st to 10th	Day	37% 28% 10% 20% 5%	6658
	11th to 20th	Day	28% 27% 12% 28% 5%	6285
	21st to end	Day	23% 27% 14% 28% 8%	6728
August	1st to 10th	Day	30% 38% 8% 19% 4	4304
	11th to 20th	Day	30% 38% 10% 17% 5%	4213
	21st to end	Day	22% 38% 8% 24% 6% 1	4445
September	1st to 10th	Day	19% 57% 8% 11% 5%	2400
	11th to 20th	Day	15% 57% 7% 14% 6%	2400
	21st to end	Day	19% 57% 6% 11% 6%	2087
October	1st to 10th	Day	37% 37% 6% 17% 3	3260
	11th to 20th	Day	33% 38% 9% 16% 4	3240
	21st to end	Day	42% 37% 10% 9% 2	3411
November	1st to 10th	Day	34% 53% 5% 6% 2	1711
	11th to 20th	Day	32% 54% 4 7% 2	1680
	21st to end	Day	38% 54% 3 2 3	1680
December	1st to 10th	Day	51% 36% 4 7% 1	2680
	11th to 20th	Day	52% 30% 2 10% 6%	3066
	21st to end	Day	57% 26% 2 11% 4	4048
January	1st to 10th	Night	61% 20% 8% 8% 3	8234
	11th to 20th	Night	61% 20% 6% 8% 4	8280
	21st to end	Night	57% 23% 4 8% 9%	8581
February	1st to 10th	Night	26% 59% 5% 6% 3	2730
	11th to 20th	Night	27% 57% 4 8% 3	2665
	21st to end	Night	28% 59% 3 6% 3 1	2184
March	1st to 10th	Night	46% 28% 6% 10% 7% 3	5220
	11th to 20th	Night	44% 29% 11% 11% 6%	5090
	21st to end	Night	45% 28% 4 14% 8% 2	5459
April	1st to 10th	Night	26% 58% 4 7% 5%	2100
	11th to 20th	Night	20% 59% 4 11% 6% 1	2055
	21st to end	Night	23% 59% 3 10% 6%	1890
May	1st to 10th	Night	39% 29% 5% 15% 7% 4	3663
	11th to 20th	Night	32% 30% 11% 15% 10% 3	3576
	21st to end	Night	41% 28% 6% 16% 8%	3927
June	1st to 10th	Night	17% 62% 3 11% 6% 1	1600
	11th to 20th	Night	16% 62% 3 10% 7% 1	1479
	21st to end	Night	18% 61% 4 10% 7% 1	1400
July	1st to 10th	Night	40% 27% 9% 18% 5%	3203
	11th to 20th	Night	31% 27% 12% 24% 6%	3552
	21st to end	Night	26% 26% 9% 30% 10%	3809
August	1st to 10th	Night	21% 38% 11% 21% 9%	2805
	11th to 20th	Night	31% 37% 10% 17% 5%	2902
	21st to end	Night	25% 37% 9% 19% 8% 2	3419
September	1st to 10th	Night	14% 59% 9% 13% 6%	2000
	11th to 20th	Night	15% 56% 5% 17% 6%	2000
	21st to end	Night	17% 57% 6% 13% 7%	2310
October	1st to 10th	Night	28% 36% 9% 19% 7%	3920
	11th to 20th	Night	32% 37% 10% 15% 6%	3899
	21st to end	Night	36% 37% 13% 10% 5%	4378
November	1st to 10th	Night	32% 53% 6% 6% 3	2805
	11th to 20th	Night	31% 54% 5% 8% 2	2940
	21st to end	Night	34% 54% 4 5% 2	2940
December	1st to 10th	Night	51% 37% 6% 5% 1	4720
	11th to 20th	Night	51% 30% 4 7% 8%	5348
	21st to end	Night	55% 25% 3 10% 6%	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	24% 21% 34% 16% 4 1	220
	11th to 20th	Day	25% 18% 35% 17% 4 1	220
	21st to end	Day	22% 17% 35% 18% 7% 1	327
February	1st to 10th	Day	25% 24% 33% 13% 5% 1	330
	11th to 20th	Day	26% 25% 38% 11%	330
	21st to end	Day	30% 19% 33% 16% 2	336
March	1st to 10th	Day	26% 19% 36% 16% 3	540
	11th to 20th	Day	30% 16% 33% 17% 4 1	540
	21st to end	Day	30% 21% 28% 15% 5% 1	594
April	1st to 10th	Day	32% 18% 29% 15% 5% 1	540
	11th to 20th	Day	33% 18% 24% 15% 8% 3	532
	21st to end	Day	31% 17% 30% 15% 7% 1	540
May	1st to 10th	Day	26% 13% 32% 18% 8% 3	507
	11th to 20th	Day	25% 15% 26% 20% 10% 4	527
	21st to end	Day	22% 14% 29% 23% 9% 3	573
June	1st to 10th	Day	25% 12% 31% 23% 7% 1	530
	11th to 20th	Day	17% 14% 32% 24% 10% 3	644
	21st to end	Day	22% 15% 31% 20% 10% 1	730
July	1st to 10th	Day	14% 11% 32% 30% 11% 2	685
	11th to 20th	Day	14% 10% 35% 26% 12% 3	524
	21st to end	Day	11% 11% 32% 29% 13% 4	576
August	1st to 10th	Day	16% 8% 30% 28% 13% 5%	526
	11th to 20th	Day	17% 8% 23% 27% 18% 7%	519
	21st to end	Day	18% 11% 29% 23% 15% 5%	583
September	1st to 10th	Day	21% 9% 29% 21% 13% 7%	530
	11th to 20th	Day	14% 11% 24% 24% 18% 9%	530
	21st to end	Day	22% 13% 24% 22% 14% 4	530
October	1st to 10th	Day	24% 16% 23% 21% 14% 2	530
	11th to 20th	Day	29% 18% 30% 17% 5% 1	530
	21st to end	Day	32% 15% 28% 20% 4	539
November	1st to 10th	Day	33% 15% 32% 14% 5%	285
	11th to 20th	Day	23% 22% 37% 12% 5%	220
	21st to end	Day	37% 19% 31% 10% 2 1	220
December	1st to 10th	Day	31% 14% 38% 12% 5%	220
	11th to 20th	Day	33% 22% 32% 9% 3 1	220
	21st to end	Day	33% 19% 28% 13% 5% 1	242
January	1st to 10th	Night	28% 13% 33% 21% 5%	840
	11th to 20th	Night	27% 15% 29% 23% 6%	840
	21st to end	Night	18% 14% 31% 28% 9% 1	924
February	1st to 10th	Night	18% 19% 34% 23% 5% 1	840
	11th to 20th	Night	23% 17% 35% 21% 4 1	823
	21st to end	Night	26% 15% 29% 25% 4	692
March	1st to 10th	Night	23% 19% 29% 25% 3	840
	11th to 20th	Night	23% 17% 32% 21% 6%	840
	21st to end	Night	23% 15% 31% 23% 7% 1	924
April	1st to 10th	Night	30% 13% 28% 24% 4	840
	11th to 20th	Night	26% 15% 26% 24% 9%	811
	21st to end	Night	27% 10% 29% 23% 10%	630
May	1st to 10th	Night	25% 8% 25% 30% 11%	431
	11th to 20th	Night	21% 9% 29% 29% 11%	394
	21st to end	Night	20% 8% 29% 33% 11%	433
June	1st to 10th	Night	19% 7% 29% 37% 8%	400
	11th to 20th	Night	18% 8% 28% 35% 12% 1	400
	21st to end	Night	22% 6% 22% 35% 15% 1	400
July	1st to 10th	Night	12% 6% 29% 40% 13% 1	390
	11th to 20th	Night	15% 4 22% 42% 17%	388
	21st to end	Night	11% 5% 25% 40% 19%	438
August	1st to 10th	Night	15% 6% 20% 36% 22% 1	536
	11th to 20th	Night	13% 5% 18% 37% 25% 2	594
	21st to end	Night	17% 8% 26% 30% 17% 2	778
September	1st to 10th	Night	16% 7% 27% 30% 19% 2	800
	11th to 20th	Night	19% 6% 21% 26% 24% 3	800
	21st to end	Night	23% 9% 20% 29% 17% 2	800
October	1st to 10th	Night	23% 10% 27% 26% 13% 1	800
	11th to 20th	Night	32% 13% 26% 21% 8% 1	800
	21st to end	Night	35% 11% 24% 25% 4	880
November	1st to 10th	Night	31% 11% 24% 27% 6% 1	820
	11th to 20th	Night	28% 17% 29% 18% 8%	840
	21st to end	Night	37% 15% 22% 22% 5%	840
December	1st to 10th	Night	33% 16% 27% 18% 5%	840
	11th to 20th	Night	28% 16% 29% 23% 4 1	840
	21st to end	Night	35% 14% 25% 22% 4	924

Page generated at 2026-04-29 02:21:45. Version ac07

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