Cold Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cold Lake clear sky chart from 2005-11-06 to 2025-04-26.

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	10% 9% 3 9% 6% 5% 5% 4 6% 8% 34%	116414
	Night	8% 10% 4 11% 6% 6% 6% 4 6% 8% 32%	120854
Transparency	Day	47% 8% 17% 22% 7%	116156
	Night	50% 7% 16% 20% 7% 1	120758
Seeing	Day	13% 8% 28% 30% 16% 4	16123
	Night	13% 6% 29% 35% 15% 2	25388

By Month

Percentage Cloud Cover NW (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	4 13% 6% 18% 10% 7% 6% 4 5% 6% 21%	3179
	11th to 20th	Day	5% 9% 3 10% 7% 7% 9% 6% 8% 9% 27%	3159
	21st to end	Day	6% 14% 6% 15% 7% 5% 4 4 5% 7% 26%	3498
February	1st to 10th	Day	6% 12% 4 11% 9% 7% 6% 6% 7% 7% 24%	1590
	11th to 20th	Day	6% 10% 5% 13% 8% 7% 6% 5% 7% 8% 27%	1755
	21st to end	Day	6% 11% 4 12% 9% 8% 6% 5% 8% 8% 25%	1485
March	1st to 10th	Day	5% 8% 3 9% 5% 6% 7% 6% 8% 11% 32%	4488
	11th to 20th	Day	5% 9% 4 11% 8% 6% 6% 4 7% 9% 32%	4999
	21st to end	Day	10% 15% 5% 11% 6% 4 5% 3 5% 7% 30%	5527
April	1st to 10th	Day	8% 12% 4 8% 6% 6% 5% 5% 7% 8% 33%	2500
	11th to 20th	Day	12% 10% 3 8% 6% 6% 6% 4 6% 7% 31%	2570
	21st to end	Day	12% 11% 3 9% 5% 6% 5% 4 6% 7% 32%	2646
May	1st to 10th	Day	14% 11% 4 9% 6% 5% 5% 4 6% 6% 30%	4523
	11th to 20th	Day	15% 10% 3 9% 5% 5% 5% 4 6% 6% 32%	4694
	21st to end	Day	12% 8% 3 9% 5% 6% 6% 5% 8% 9% 30%	5220
June	1st to 10th	Day	17% 6% 3 8% 5% 5% 6% 5% 6% 8% 30%	3040
	11th to 20th	Day	20% 9% 3 8% 5% 6% 5% 4 8% 7% 25%	3040
	21st to end	Day	12% 8% 3 8% 5% 6% 6% 4 7% 8% 33%	3040
July	1st to 10th	Day	8% 5% 2 5% 4 5% 6% 4 7% 10% 45%	4908
	11th to 20th	Day	8% 4 2 5% 3 5% 5% 5% 7% 11% 46%	4740
	21st to end	Day	13% 5% 2 5% 4 5% 5% 5% 7% 8% 42%	5138
August	1st to 10th	Day	11% 6% 3 6% 4 4 4 3 5% 7% 46%	4699
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 9% 42%	4129
	21st to end	Day	9% 5% 2 6% 4 4 4 4 7% 8% 46%	4521
September	1st to 10th	Day	13% 7% 2 7% 4 4 4 4 5% 8% 42%	2366
	11th to 20th	Day	17% 8% 2 6% 4 3 4 3 5% 8% 40%	2197
	21st to end	Day	9% 7% 2 7% 5% 4 5% 4 7% 8% 41%	2060
October	1st to 10th	Day	10% 9% 3 8% 5% 4 5% 4 6% 8% 38%	3170
	11th to 20th	Day	12% 9% 3 8% 5% 5% 4 4 7% 9% 35%	3071
	21st to end	Day	8% 15% 5% 9% 6% 5% 6% 5% 6% 7% 29%	2822
November	1st to 10th	Day	11% 15% 4 12% 7% 6% 5% 3 5% 7% 24%	1568
	11th to 20th	Day	9% 14% 5% 14% 7% 5% 6% 5% 7% 6% 22%	1535
	21st to end	Day	6% 12% 5% 13% 7% 7% 6% 4 6% 6% 28%	1303
December	1st to 10th	Day	6% 12% 5% 17% 10% 6% 6% 5% 7% 7% 20%	1960
	11th to 20th	Day	8% 16% 6% 15% 7% 6% 5% 4 5% 6% 22%	2259
	21st to end	Day	3 10% 4 12% 8% 6% 6% 5% 6% 6% 34%	3015
January	1st to 10th	Night	4 10% 5% 17% 10% 8% 8% 4 6% 7% 19%	6766
	11th to 20th	Night	4 9% 3 10% 8% 8% 9% 5% 7% 9% 28%	6739
	21st to end	Night	5% 11% 6% 13% 7% 6% 5% 4 6% 7% 30%	7458
February	1st to 10th	Night	7% 12% 4 12% 8% 7% 6% 5% 6% 7% 26%	2830
	11th to 20th	Night	6% 11% 4 10% 8% 7% 5% 4 6% 7% 32%	2532
	21st to end	Night	3 10% 5% 10% 7% 7% 7% 6% 7% 7% 29%	2145
March	1st to 10th	Night	5% 10% 4 12% 7% 7% 6% 5% 7% 10% 26%	5384
	11th to 20th	Night	5% 11% 4 10% 7% 6% 7% 5% 7% 8% 30%	5000
	21st to end	Night	9% 16% 5% 10% 6% 5% 5% 4 5% 7% 28%	5446
April	1st to 10th	Night	7% 10% 3 9% 5% 6% 5% 4 7% 9% 35%	1897
	11th to 20th	Night	10% 9% 3 9% 6% 5% 6% 4 8% 7% 33%	1781
	21st to end	Night	12% 10% 4 8% 5% 4 3 5% 5% 7% 36%	1649
May	1st to 10th	Night	15% 12% 4 8% 6% 4 4 4 6% 8% 30%	2429
	11th to 20th	Night	17% 7% 3 8% 5% 4 4 5% 5% 6% 36%	2199
	21st to end	Night	14% 10% 3 8% 6% 6% 5% 5% 7% 8% 29%	2354
June	1st to 10th	Night	17% 7% 4 7% 5% 4 5% 4 6% 7% 33%	1140
	11th to 20th	Night	17% 10% 2 8% 6% 6% 6% 4 7% 9% 24%	1140
	21st to end	Night	13% 5% 2 6% 5% 5% 6% 5% 7% 9% 39%	1140
July	1st to 10th	Night	8% 4 2 5% 3 4 4 4 9% 9% 49%	2049
	11th to 20th	Night	6% 4 1 4 4 4 5% 4 7% 9% 52%	2220
	21st to end	Night	15% 5% 2 5% 3 3 4 3 6% 8% 45%	2414
August	1st to 10th	Night	12% 6% 3 6% 4 4 5% 4 7% 7% 44%	2232
	11th to 20th	Night	7% 4 2 7% 5% 5% 6% 5% 8% 10% 41%	2709
	21st to end	Night	8% 5% 2 6% 5% 4 5% 4 6% 7% 47%	3146
September	1st to 10th	Night	14% 6% 2 6% 3 4 4 4 6% 7% 44%	1814
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 4 6% 8% 44%	1981
	21st to end	Night	8% 6% 2 5% 4 4 6% 4 7% 9% 45%	2119
October	1st to 10th	Night	9% 6% 2 7% 4 5% 5% 4 7% 8% 42%	3800
	11th to 20th	Night	10% 8% 3 7% 5% 4 5% 4 6% 9% 39%	3855
	21st to end	Night	11% 13% 4 9% 5% 5% 6% 4 6% 8% 28%	4705
November	1st to 10th	Night	12% 16% 6% 9% 7% 5% 5% 4 5% 6% 25%	2730
	11th to 20th	Night	9% 14% 5% 15% 7% 5% 5% 4 6% 6% 24%	2864
	21st to end	Night	6% 13% 6% 13% 8% 6% 5% 4 7% 7% 26%	3095
December	1st to 10th	Night	9% 14% 5% 16% 7% 7% 5% 4 6% 7% 20%	5220
	11th to 20th	Night	6% 15% 6% 17% 8% 6% 6% 4 6% 7% 18%	5933
	21st to end	Night	3 8% 5% 14% 8% 6% 5% 4 5% 5% 36%	7939

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	63% 5% 10% 17% 5%	3179
	11th to 20th	Day	51% 7% 14% 16% 11% 1	3180
	21st to end	Day	57% 7% 21% 11% 4	3498
February	1st to 10th	Day	55% 9% 13% 13% 11%	1590
	11th to 20th	Day	52% 7% 15% 18% 8% 1	1764
	21st to end	Day	55% 6% 15% 17% 7%	1485
March	1st to 10th	Day	42% 7% 21% 25% 6%	4488
	11th to 20th	Day	46% 8% 15% 24% 8%	5000
	21st to end	Day	52% 7% 11% 19% 12%	5527
April	1st to 10th	Day	47% 8% 16% 19% 9%	2500
	11th to 20th	Day	52% 6% 12% 20% 9% 1	2570
	21st to end	Day	49% 7% 13% 22% 8% 1	2646
May	1st to 10th	Day	51% 8% 12% 19% 9% 1	4523
	11th to 20th	Day	49% 8% 11% 20% 11% 1	4698
	21st to end	Day	46% 11% 16% 19% 8%	5221
June	1st to 10th	Day	48% 10% 15% 17% 9% 1	3040
	11th to 20th	Day	55% 9% 13% 18% 4 1	3040
	21st to end	Day	46% 10% 15% 22% 6% 1	3040
July	1st to 10th	Day	32% 9% 28% 26% 5%	4833
	11th to 20th	Day	31% 8% 19% 31% 11%	4659
	21st to end	Day	37% 10% 22% 28% 3	4976
August	1st to 10th	Day	37% 8% 21% 32% 2	4681
	11th to 20th	Day	36% 9% 25% 24% 5%	4171
	21st to end	Day	35% 7% 27% 28% 3	4520
September	1st to 10th	Day	40% 9% 17% 26% 8% 1	2366
	11th to 20th	Day	43% 7% 21% 25% 4	2197
	21st to end	Day	39% 8% 18% 23% 9% 1	2060
October	1st to 10th	Day	45% 6% 18% 27% 4	3170
	11th to 20th	Day	46% 6% 18% 26% 4	3071
	21st to end	Day	56% 8% 18% 15% 3	2822
November	1st to 10th	Day	62% 9% 13% 13% 4	1568
	11th to 20th	Day	63% 8% 14% 12% 3	1535
	21st to end	Day	58% 9% 13% 16% 4 1	1303
December	1st to 10th	Day	64% 7% 10% 15% 4 1	1960
	11th to 20th	Day	65% 6% 12% 14% 3	2260
	21st to end	Day	50% 5% 14% 23% 7% 1	3015
January	1st to 10th	Night	62% 7% 12% 13% 7%	6766
	11th to 20th	Night	53% 6% 14% 16% 11% 1	6780
	21st to end	Night	53% 7% 22% 13% 4	7458
February	1st to 10th	Night	54% 7% 12% 17% 9%	2830
	11th to 20th	Night	49% 6% 13% 22% 9%	2533
	21st to end	Night	50% 8% 15% 17% 10%	2145
March	1st to 10th	Night	51% 6% 17% 18% 7%	5384
	11th to 20th	Night	46% 9% 16% 23% 6%	5000
	21st to end	Night	53% 5% 11% 17% 14%	5446
April	1st to 10th	Night	44% 7% 14% 20% 14%	1897
	11th to 20th	Night	46% 7% 11% 19% 14% 3	1781
	21st to end	Night	46% 7% 12% 21% 12% 2	1649
May	1st to 10th	Night	51% 6% 8% 24% 9% 1	2429
	11th to 20th	Night	45% 8% 10% 25% 12% 1	2199
	21st to end	Night	46% 12% 17% 17% 6% 1	2354
June	1st to 10th	Night	48% 8% 13% 18% 11% 2	1140
	11th to 20th	Night	52% 11% 14% 15% 7% 1	1140
	21st to end	Night	40% 9% 17% 22% 11% 1	1140
July	1st to 10th	Night	28% 9% 26% 28% 8% 1	2015
	11th to 20th	Night	27% 7% 16% 38% 11%	2178
	21st to end	Night	37% 7% 24% 26% 6%	2337
August	1st to 10th	Night	36% 7% 19% 36% 2	2225
	11th to 20th	Night	35% 9% 28% 22% 6%	2733
	21st to end	Night	36% 6% 23% 32% 4	3146
September	1st to 10th	Night	39% 6% 20% 25% 8% 2	1814
	11th to 20th	Night	40% 7% 19% 26% 8%	1981
	21st to end	Night	34% 8% 17% 29% 10% 2	2119
October	1st to 10th	Night	39% 5% 22% 28% 6%	3800
	11th to 20th	Night	42% 5% 17% 29% 6%	3855
	21st to end	Night	55% 6% 18% 17% 4	4705
November	1st to 10th	Night	62% 8% 10% 16% 5%	2730
	11th to 20th	Night	62% 9% 14% 11% 4	2864
	21st to end	Night	58% 8% 16% 15% 3	3095
December	1st to 10th	Night	64% 7% 12% 12% 5%	5220
	11th to 20th	Night	65% 7% 15% 10% 3	5931
	21st to end	Night	49% 5% 12% 22% 10% 1	7939

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	11% 4 27% 36% 17% 7%	200
	11th to 20th	Day	14% 7% 26% 37% 12% 5%	200
	21st to end	Day	10% 11% 34% 35% 7% 3	220
February	1st to 10th	Day	9% 6% 38% 33% 11% 3	223
	11th to 20th	Day	7% 8% 29% 31% 21% 4	300
	21st to end	Day	7% 8% 31% 36% 14% 3	249
March	1st to 10th	Day	10% 8% 33% 35% 13% 1	405
	11th to 20th	Day	10% 10% 37% 28% 11% 3	500
	21st to end	Day	17% 6% 33% 31% 11% 2	550
April	1st to 10th	Day	9% 11% 36% 31% 11% 2	500
	11th to 20th	Day	17% 10% 32% 26% 11% 3	492
	21st to end	Day	13% 11% 33% 31% 10% 3	590
May	1st to 10th	Day	11% 11% 28% 29% 17% 5%	653
	11th to 20th	Day	10% 8% 26% 31% 18% 7%	675
	21st to end	Day	16% 7% 23% 29% 19% 5%	734
June	1st to 10th	Day	19% 10% 29% 28% 12% 3	680
	11th to 20th	Day	20% 10% 26% 25% 15% 5%	680
	21st to end	Day	11% 5% 21% 32% 22% 9%	680
July	1st to 10th	Day	12% 5% 22% 31% 25% 6%	671
	11th to 20th	Day	10% 5% 23% 33% 23% 6%	668
	21st to end	Day	9% 5% 26% 29% 22% 8%	739
August	1st to 10th	Day	13% 5% 18% 29% 26% 8%	676
	11th to 20th	Day	10% 6% 23% 36% 21% 4	542
	21st to end	Day	10% 8% 24% 31% 21% 6%	539
September	1st to 10th	Day	14% 11% 29% 27% 16% 3	490
	11th to 20th	Day	21% 7% 23% 30% 17% 3	490
	21st to end	Day	11% 13% 32% 28% 12% 3	460
October	1st to 10th	Day	13% 9% 29% 32% 14% 3	300
	11th to 20th	Day	18% 9% 35% 27% 11%	300
	21st to end	Day	17% 14% 30% 26% 11% 2	330
November	1st to 10th	Day	16% 11% 26% 32% 14% 2	300
	11th to 20th	Day	16% 9% 43% 25% 4 3	267
	21st to end	Day	10% 10% 35% 32% 9% 6%	200
December	1st to 10th	Day	7% 7% 35% 35% 15% 3	200
	11th to 20th	Day	11% 8% 42% 31% 9% 1	200
	21st to end	Day	7% 5% 28% 34% 20% 6%	220
January	1st to 10th	Night	12% 6% 29% 37% 15% 2	1000
	11th to 20th	Night	11% 5% 31% 39% 12% 2	1000
	21st to end	Night	13% 9% 37% 31% 8% 2	1100
February	1st to 10th	Night	11% 6% 26% 39% 16% 2	875
	11th to 20th	Night	10% 4 32% 35% 17% 2	784
	21st to end	Night	7% 4 25% 43% 19% 3	660
March	1st to 10th	Night	10% 4 31% 40% 13% 2	800
	11th to 20th	Night	12% 6% 31% 37% 13% 2	800
	21st to end	Night	14% 8% 25% 35% 16% 2	862
April	1st to 10th	Night	9% 5% 31% 39% 15% 1	600
	11th to 20th	Night	13% 7% 33% 33% 13% 2	593
	21st to end	Night	17% 7% 27% 33% 15% 1	587
May	1st to 10th	Night	14% 9% 26% 33% 16% 1	511
	11th to 20th	Night	12% 4 28% 38% 15% 3	374
	21st to end	Night	16% 5% 23% 34% 19% 3	411
June	1st to 10th	Night	18% 7% 23% 32% 18% 1	380
	11th to 20th	Night	20% 6% 22% 30% 20% 2	380
	21st to end	Night	13% 2 19% 34% 28% 4	380
July	1st to 10th	Night	11% 3 20% 36% 29% 1	370
	11th to 20th	Night	12% 2 19% 40% 25% 2	368
	21st to end	Night	10% 3 19% 41% 22% 6%	416
August	1st to 10th	Night	11% 1 17% 37% 27% 6%	387
	11th to 20th	Night	9% 3 19% 40% 27% 2	564
	21st to end	Night	11% 4 24% 39% 21% 2	627
September	1st to 10th	Night	18% 3 25% 32% 21% 1	570
	11th to 20th	Night	13% 6% 24% 38% 19% 1	651
	21st to end	Night	10% 6% 32% 36% 14% 1	760
October	1st to 10th	Night	16% 6% 31% 35% 10% 2	760
	11th to 20th	Night	15% 6% 32% 33% 13% 2	760
	21st to end	Night	17% 10% 33% 30% 9% 1	983
November	1st to 10th	Night	18% 7% 30% 33% 10% 2	975
	11th to 20th	Night	16% 6% 33% 31% 11% 3	1000
	21st to end	Night	11% 6% 39% 33% 9% 1	1000
December	1st to 10th	Night	14% 6% 33% 30% 15% 3	1000
	11th to 20th	Night	12% 7% 32% 38% 10% 2	1000
	21st to end	Night	9% 4 28% 36% 20% 3	1100

Page generated at 2025-04-23 07:25:02. Version ac07

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