Halfway Lake Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Halfway Lake Provincial Park clear sky chart from 2005-11-06 to 2026-07-31.

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	15% 12% 4 9% 5% 5% 4 4 5% 6% 30%	138303
	Night	14% 14% 5% 10% 6% 5% 4 3 5% 6% 27%	134882
Transparency	Day	53% 5% 10% 20% 10% 1	141769
	Night	57% 5% 10% 18% 9% 1	139504
Seeing	Day	23% 17% 33% 18% 7% 2	17623
	Night	23% 14% 33% 23% 7% 1	26715

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	11% 18% 8% 14% 7% 5% 5% 4 5% 4 17%	4094
	11th to 20th	Day	8% 17% 8% 17% 9% 6% 4 5% 4 5% 17%	4438
	21st to end	Day	8% 16% 8% 17% 7% 6% 4 4 6% 6% 17%	5363
February	1st to 10th	Day	8% 17% 6% 12% 9% 7% 6% 4 5% 5% 19%	1890
	11th to 20th	Day	10% 18% 5% 13% 7% 5% 4 4 6% 6% 23%	1843
	21st to end	Day	10% 20% 6% 13% 7% 5% 4 3 4 6% 22%	1668
March	1st to 10th	Day	15% 17% 4 9% 5% 4 3 3 5% 6% 28%	4801
	11th to 20th	Day	16% 14% 4 10% 6% 5% 4 3 5% 6% 25%	5090
	21st to end	Day	15% 15% 7% 13% 4 4 4 3 4 5% 29%	5586
April	1st to 10th	Day	19% 14% 4 10% 5% 4 4 3 5% 6% 26%	2494
	11th to 20th	Day	20% 13% 4 8% 5% 4 4 3 4 6% 30%	2702
	21st to end	Day	20% 11% 4 7% 4 4 3 3 4 6% 33%	2730
May	1st to 10th	Day	15% 10% 3 9% 5% 5% 5% 4 5% 6% 34%	7642
	11th to 20th	Day	16% 10% 3 7% 4 4 4 4 5% 6% 37%	8180
	21st to end	Day	18% 8% 2 6% 4 4 4 4 4 7% 41%	9534
June	1st to 10th	Day	17% 8% 3 8% 6% 5% 5% 4 5% 7% 32%	3150
	11th to 20th	Day	14% 8% 3 7% 6% 5% 5% 5% 5% 8% 34%	3150
	21st to end	Day	17% 9% 4 7% 6% 5% 6% 4 6% 6% 31%	3150
July	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 5% 7% 9% 31%	6969
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 9% 38%	6970
	21st to end	Day	12% 6% 2 6% 4 4 4 4 7% 9% 43%	7059
August	1st to 10th	Day	10% 7% 3 8% 5% 5% 5% 5% 7% 9% 36%	4234
	11th to 20th	Day	18% 7% 2 6% 5% 4 4 3 5% 8% 37%	4174
	21st to end	Day	14% 7% 3 7% 5% 4 4 3 6% 8% 40%	4675
September	1st to 10th	Day	15% 9% 3 7% 5% 4 5% 3 6% 7% 34%	2404
	11th to 20th	Day	16% 8% 2 7% 5% 4 4 4 5% 7% 39%	2200
	21st to end	Day	21% 10% 2 7% 3 4 3 3 5% 6% 35%	2200
October	1st to 10th	Day	20% 14% 3 7% 3 4 4 3 5% 5% 32%	2035
	11th to 20th	Day	25% 15% 4 10% 4 4 4 3 3 5% 22%	2000
	21st to end	Day	24% 19% 5% 9% 4 4 3 3 5% 5% 19%	2035
November	1st to 10th	Day	18% 18% 5% 10% 6% 4 4 2 5% 5% 23%	1747
	11th to 20th	Day	18% 17% 6% 14% 7% 5% 4 3 5% 6% 17%	1680
	21st to end	Day	21% 25% 7% 11% 6% 5% 3 3 3 4 13%	1680
December	1st to 10th	Day	14% 20% 11% 19% 7% 5% 4 3 3 3 11%	2492
	11th to 20th	Day	14% 23% 5% 14% 5% 4 3 3 5% 5% 20%	2691
	21st to end	Day	21% 22% 9% 16% 6% 3 2 2 3 5% 13%	3553
January	1st to 10th	Night	9% 15% 7% 17% 10% 9% 6% 4 5% 5% 13%	8831
	11th to 20th	Night	10% 20% 9% 15% 7% 5% 5% 4 4 4 17%	8475
	21st to end	Night	7% 14% 8% 15% 8% 8% 6% 4 5% 6% 18%	8837
February	1st to 10th	Night	9% 17% 5% 11% 9% 6% 5% 5% 6% 7% 20%	2730
	11th to 20th	Night	9% 16% 6% 14% 8% 6% 5% 3 5% 6% 21%	2663
	21st to end	Night	11% 17% 6% 11% 8% 6% 5% 4 5% 6% 22%	2134
March	1st to 10th	Night	16% 14% 4 11% 5% 4 4 3 5% 6% 29%	5259
	11th to 20th	Night	16% 12% 6% 11% 7% 5% 5% 3 5% 6% 25%	5089
	21st to end	Night	16% 13% 5% 12% 5% 5% 4 3 4 5% 28%	5588
April	1st to 10th	Night	18% 14% 4 8% 5% 5% 4 4 5% 6% 27%	2143
	11th to 20th	Night	19% 11% 3 8% 5% 3 3 3 5% 6% 34%	1867
	21st to end	Night	17% 11% 4 8% 5% 4 5% 3 5% 5% 34%	1890
May	1st to 10th	Night	13% 11% 4 8% 4 4 4 3 5% 6% 38%	5257
	11th to 20th	Night	15% 11% 3 7% 4 4 4 3 5% 7% 37%	4665
	21st to end	Night	15% 10% 2 5% 3 4 4 3 4 7% 43%	4661
June	1st to 10th	Night	14% 7% 3 8% 4 5% 5% 4 7% 7% 36%	1470
	11th to 20th	Night	14% 6% 2 5% 4 4 6% 5% 8% 9% 37%	1470
	21st to end	Night	14% 6% 2 7% 5% 4 4 3 7% 7% 40%	1470
July	1st to 10th	Night	15% 7% 3 6% 4 5% 4 4 6% 6% 41%	3230
	11th to 20th	Night	12% 5% 2 6% 5% 3 5% 4 5% 8% 45%	3230
	21st to end	Night	10% 6% 2 5% 3 4 4 4 6% 9% 47%	4009
August	1st to 10th	Night	9% 6% 2 8% 5% 5% 5% 4 7% 8% 40%	2915
	11th to 20th	Night	15% 8% 3 5% 4 4 4 3 5% 7% 42%	2875
	21st to end	Night	12% 6% 2 7% 4 3 4 3 5% 7% 47%	3223
September	1st to 10th	Night	15% 8% 3 5% 3 4 4 4 5% 7% 42%	1972
	11th to 20th	Night	15% 7% 2 5% 4 4 4 3 5% 6% 46%	2200
	21st to end	Night	17% 9% 3 5% 5% 4 4 3 5% 7% 39%	2200
October	1st to 10th	Night	20% 11% 2 6% 4 4 3 3 5% 6% 36%	2365
	11th to 20th	Night	24% 15% 3 7% 4 3 4 3 5% 6% 24%	2400
	21st to end	Night	23% 17% 5% 9% 5% 4 3 3 3 5% 22%	2801
November	1st to 10th	Night	16% 16% 5% 9% 6% 5% 4 3 5% 6% 26%	2770
	11th to 20th	Night	18% 16% 5% 11% 6% 5% 5% 3 4 6% 21%	2940
	21st to end	Night	20% 19% 6% 12% 6% 5% 4 3 5% 5% 14%	2940
December	1st to 10th	Night	13% 22% 8% 16% 7% 5% 4 3 4 5% 12%	4910
	11th to 20th	Night	12% 21% 6% 13% 7% 7% 5% 3 5% 5% 16%	5736
	21st to end	Night	21% 24% 6% 12% 7% 4 3 3 4 4 12%	7667

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	68% 3 10% 12% 4 3	4095
	11th to 20th	Day	69% 4 7% 10% 9% 1	4468
	21st to end	Day	67% 3 5% 15% 10%	5363
February	1st to 10th	Day	63% 5% 9% 14% 8% 1	1890
	11th to 20th	Day	60% 5% 11% 13% 10% 1	1852
	21st to end	Day	63% 4 7% 16% 10% 1	1668
March	1st to 10th	Day	58% 4 10% 11% 15% 4	4804
	11th to 20th	Day	59% 4 12% 14% 10% 1	5090
	21st to end	Day	59% 3 10% 15% 11% 2	5586
April	1st to 10th	Day	59% 4 10% 17% 8% 2	2494
	11th to 20th	Day	55% 5% 8% 20% 11% 1	2702
	21st to end	Day	53% 4 10% 16% 15% 2	2730
May	1st to 10th	Day	50% 5% 7% 20% 15% 3	7651
	11th to 20th	Day	46% 5% 9% 22% 15% 3	8184
	21st to end	Day	43% 5% 9% 22% 17% 4	9535
June	1st to 10th	Day	49% 6% 10% 20% 13% 2	3150
	11th to 20th	Day	47% 6% 11% 21% 14% 1	3150
	21st to end	Day	51% 7% 10% 20% 11% 1	3150
July	1st to 10th	Day	45% 7% 12% 25% 9%	6896
	11th to 20th	Day	39% 6% 17% 30% 7%	6889
	21st to end	Day	36% 5% 13% 35% 10%	6860
August	1st to 10th	Day	42% 6% 13% 30% 8% 1	4221
	11th to 20th	Day	45% 5% 13% 28% 8%	4213
	21st to end	Day	43% 5% 12% 30% 9% 1	4674
September	1st to 10th	Day	48% 6% 12% 23% 9% 1	2404
	11th to 20th	Day	44% 5% 14% 27% 9%	2200
	21st to end	Day	50% 6% 13% 22% 9%	2200
October	1st to 10th	Day	47% 5% 11% 26% 12%	3308
	11th to 20th	Day	54% 4 10% 20% 11%	3240
	21st to end	Day	66% 4 13% 11% 6%	3259
November	1st to 10th	Day	62% 7% 11% 15% 6%	1747
	11th to 20th	Day	68% 6% 9% 12% 4	1680
	21st to end	Day	76% 4 9% 9% 3	1680
December	1st to 10th	Day	77% 4 8% 7% 3	2492
	11th to 20th	Day	68% 3 7% 15% 7% 1	2691
	21st to end	Day	76% 2 4 10% 7%	3553
January	1st to 10th	Night	71% 4 8% 12% 5% 1	8831
	11th to 20th	Night	70% 3 7% 11% 8%	8520
	21st to end	Night	66% 4 6% 13% 10% 1	8837
February	1st to 10th	Night	61% 5% 10% 15% 8% 1	2730
	11th to 20th	Night	62% 5% 12% 14% 7% 1	2665
	21st to end	Night	61% 4 10% 14% 9% 1	2134
March	1st to 10th	Night	57% 3 8% 16% 13% 4	5269
	11th to 20th	Night	60% 4 11% 16% 7% 1	5090
	21st to end	Night	59% 4 7% 15% 12% 3	5588
April	1st to 10th	Night	55% 5% 10% 18% 11% 1	2143
	11th to 20th	Night	51% 3 8% 21% 15% 1	1867
	21st to end	Night	51% 5% 11% 17% 14% 2	1890
May	1st to 10th	Night	47% 5% 7% 23% 16% 3	5264
	11th to 20th	Night	45% 5% 11% 24% 12% 3	4666
	21st to end	Night	42% 4 9% 28% 14% 4	4662
June	1st to 10th	Night	43% 7% 12% 21% 12% 3	1470
	11th to 20th	Night	39% 7% 15% 22% 16% 1	1470
	21st to end	Night	41% 6% 15% 24% 12% 1	1470
July	1st to 10th	Night	42% 6% 12% 30% 10% 1	3195
	11th to 20th	Night	36% 5% 13% 36% 9% 1	3188
	21st to end	Night	34% 6% 16% 32% 13%	3894
August	1st to 10th	Night	39% 7% 17% 26% 10%	2904
	11th to 20th	Night	41% 6% 17% 30% 7%	2902
	21st to end	Night	37% 6% 14% 30% 13% 1	3223
September	1st to 10th	Night	40% 7% 15% 26% 9% 2	1972
	11th to 20th	Night	39% 5% 15% 31% 10% 1	2200
	21st to end	Night	44% 6% 16% 26% 9%	2200
October	1st to 10th	Night	45% 4 12% 28% 10%	3872
	11th to 20th	Night	54% 4 12% 21% 8%	3899
	21st to end	Night	61% 5% 17% 12% 4 1	4527
November	1st to 10th	Night	58% 6% 13% 17% 6%	2770
	11th to 20th	Night	64% 6% 12% 13% 5%	2940
	21st to end	Night	71% 6% 11% 8% 5% 1	2940
December	1st to 10th	Night	73% 4 9% 10% 2	4910
	11th to 20th	Night	69% 4 8% 12% 7%	5735
	21st to end	Night	75% 3 6% 11% 5%	7667

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	25% 19% 37% 12% 6%	220
	11th to 20th	Day	21% 18% 35% 21% 4 1	286
	21st to end	Day	21% 15% 41% 17% 5%	363
February	1st to 10th	Day	25% 30% 31% 12% 3	330
	11th to 20th	Day	21% 29% 38% 10% 2	330
	21st to end	Day	28% 28% 35% 8%	273
March	1st to 10th	Day	26% 25% 34% 13% 1	424
	11th to 20th	Day	26% 21% 33% 16% 3 1	540
	21st to end	Day	29% 19% 36% 11% 4 1	594
April	1st to 10th	Day	29% 17% 34% 16% 4 1	540
	11th to 20th	Day	34% 19% 21% 17% 6% 3	532
	21st to end	Day	31% 19% 26% 16% 6% 1	540
May	1st to 10th	Day	24% 17% 33% 18% 6% 3	543
	11th to 20th	Day	23% 19% 30% 20% 6% 2	567
	21st to end	Day	22% 17% 33% 21% 5% 1	779
June	1st to 10th	Day	19% 16% 38% 19% 6% 1	780
	11th to 20th	Day	22% 18% 34% 19% 6% 1	780
	21st to end	Day	20% 16% 34% 20% 8% 2	780
July	1st to 10th	Day	13% 14% 40% 24% 9% 1	771
	11th to 20th	Day	15% 14% 35% 24% 9% 3	768
	21st to end	Day	15% 11% 36% 26% 8% 4	790
August	1st to 10th	Day	16% 12% 28% 27% 12% 5%	526
	11th to 20th	Day	17% 6% 29% 24% 17% 7%	519
	21st to end	Day	19% 11% 33% 18% 13% 5%	583
September	1st to 10th	Day	22% 10% 32% 21% 12% 3	530
	11th to 20th	Day	19% 10% 27% 26% 14% 5%	530
	21st to end	Day	28% 12% 29% 18% 11% 2	530
October	1st to 10th	Day	26% 18% 27% 17% 10% 1	530
	11th to 20th	Day	30% 20% 33% 13% 3 1	530
	21st to end	Day	31% 21% 32% 15% 1 1	418
November	1st to 10th	Day	34% 20% 31% 13% 2	275
	11th to 20th	Day	30% 20% 35% 12% 3	220
	21st to end	Day	38% 18% 31% 10% 2	220
December	1st to 10th	Day	25% 18% 37% 17% 3	220
	11th to 20th	Day	32% 20% 37% 9% 2	220
	21st to end	Day	30% 21% 34% 11% 2 1	242
January	1st to 10th	Night	23% 16% 38% 18% 5% 1	1050
	11th to 20th	Night	24% 16% 33% 22% 4	1050
	21st to end	Night	19% 13% 35% 23% 9% 1	1077
February	1st to 10th	Night	18% 18% 40% 18% 5%	840
	11th to 20th	Night	18% 19% 38% 20% 5%	823
	21st to end	Night	23% 18% 35% 20% 3	692
March	1st to 10th	Night	21% 21% 36% 19% 3	840
	11th to 20th	Night	27% 18% 33% 17% 4 1	840
	21st to end	Night	22% 16% 37% 18% 6% 1	924
April	1st to 10th	Night	26% 19% 30% 21% 4	777
	11th to 20th	Night	25% 16% 29% 22% 7% 1	623
	21st to end	Night	25% 13% 30% 23% 9% 1	630
May	1st to 10th	Night	17% 10% 35% 31% 7% 1	630
	11th to 20th	Night	19% 15% 32% 27% 8% 1	428
	21st to end	Night	19% 13% 36% 28% 5%	455
June	1st to 10th	Night	18% 8% 37% 31% 5%	420
	11th to 20th	Night	18% 12% 33% 29% 7%	420
	21st to end	Night	15% 10% 30% 34% 10% 1	420
July	1st to 10th	Night	11% 8% 38% 36% 7%	410
	11th to 20th	Night	11% 6% 35% 35% 12%	408
	21st to end	Night	13% 5% 30% 36% 14% 1	625
August	1st to 10th	Night	14% 4 29% 34% 17% 1	597
	11th to 20th	Night	17% 5% 26% 31% 19% 3	594
	21st to end	Night	19% 7% 28% 28% 17% 2	660
September	1st to 10th	Night	19% 8% 30% 25% 17% 1	745
	11th to 20th	Night	19% 7% 27% 29% 15% 3	800
	21st to end	Night	22% 9% 25% 29% 12% 2	800
October	1st to 10th	Night	26% 9% 30% 25% 9% 1	800
	11th to 20th	Night	31% 13% 30% 20% 5% 1	800
	21st to end	Night	32% 12% 30% 23% 3 1	880
November	1st to 10th	Night	27% 14% 34% 20% 5%	820
	11th to 20th	Night	29% 16% 30% 20% 5%	840
	21st to end	Night	32% 15% 33% 17% 3 1	840
December	1st to 10th	Night	24% 19% 33% 20% 4	952
	11th to 20th	Night	27% 17% 36% 14% 5% 1	1050
	21st to end	Night	30% 18% 31% 16% 5%	1155

Page generated at 2026-07-28 03:25:24. Version ac07

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