Dease Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dease Lake clear sky chart from 2005-11-06 to 2024-02-05.

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% 12% 6% 11% 9% 5% 7% 6% 6% 7% 21%	76863
	Night	6% 12% 6% 11% 10% 6% 8% 7% 7% 8% 20%	81943
Transparency	Day	59% 10% 14% 12% 4 1	76531
	Night	58% 10% 14% 12% 5% 1	81856
Seeing	Day	17% 13% 24% 24% 17% 5%	15997
	Night	13% 10% 24% 31% 19% 3	23407

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	3 12% 7% 14% 14% 7% 9% 8% 9% 6% 11%	1713
	11th to 20th	Day	2 17% 6% 14% 8% 4 6% 7% 6% 9% 21%	1882
	21st to end	Day	4 20% 9% 12% 10% 5% 8% 5% 6% 7% 13%	2215
February	1st to 10th	Day	5% 11% 6% 12% 9% 5% 8% 8% 9% 8% 20%	1420
	11th to 20th	Day	3 11% 8% 10% 10% 6% 8% 8% 7% 8% 21%	1400
	21st to end	Day	2 8% 8% 13% 10% 5% 9% 7% 8% 6% 23%	1332
March	1st to 10th	Day	3 11% 4 10% 11% 7% 8% 8% 8% 7% 23%	1800
	11th to 20th	Day	1 10% 8% 15% 12% 6% 8% 7% 7% 8% 19%	1898
	21st to end	Day	3 12% 8% 13% 10% 5% 7% 6% 6% 8% 22%	2290
April	1st to 10th	Day	3 12% 10% 14% 10% 5% 7% 6% 7% 7% 17%	2258
	11th to 20th	Day	4 13% 10% 13% 10% 5% 7% 6% 6% 6% 20%	2308
	21st to end	Day	5% 18% 7% 13% 9% 5% 7% 6% 6% 6% 18%	2577
May	1st to 10th	Day	8% 18% 7% 10% 7% 4 7% 7% 5% 6% 21%	2700
	11th to 20th	Day	10% 14% 5% 9% 8% 4 6% 6% 5% 6% 27%	2699
	21st to end	Day	13% 11% 5% 8% 7% 4 5% 5% 7% 8% 27%	3230
June	1st to 10th	Day	15% 12% 5% 9% 8% 4 6% 6% 7% 7% 23%	3060
	11th to 20th	Day	15% 11% 5% 10% 10% 5% 6% 5% 5% 7% 20%	3060
	21st to end	Day	14% 10% 5% 10% 8% 5% 6% 6% 7% 7% 21%	3060
July	1st to 10th	Day	13% 8% 4 8% 9% 4 6% 6% 8% 8% 26%	3060
	11th to 20th	Day	18% 10% 5% 9% 8% 4 6% 6% 5% 8% 21%	2916
	21st to end	Day	18% 8% 4 8% 7% 4 6% 5% 5% 7% 27%	3116
August	1st to 10th	Day	13% 8% 4 7% 7% 4 6% 6% 6% 8% 31%	2686
	11th to 20th	Day	18% 11% 4 8% 8% 5% 7% 6% 6% 7% 21%	2499
	21st to end	Day	19% 12% 4 9% 8% 5% 6% 6% 5% 6% 21%	2631
September	1st to 10th	Day	16% 11% 4 10% 9% 5% 5% 5% 5% 8% 22%	2301
	11th to 20th	Day	13% 11% 4 9% 8% 5% 5% 6% 6% 7% 27%	2044
	21st to end	Day	16% 14% 5% 10% 9% 5% 6% 6% 7% 6% 15%	1980
October	1st to 10th	Day	9% 11% 4 9% 8% 5% 7% 8% 7% 8% 25%	1795
	11th to 20th	Day	8% 14% 6% 10% 11% 5% 7% 6% 6% 7% 20%	1620
	21st to end	Day	7% 13% 6% 12% 9% 7% 8% 7% 7% 8% 17%	1698
November	1st to 10th	Day	5% 16% 7% 12% 9% 5% 9% 7% 8% 7% 14%	1302
	11th to 20th	Day	5% 15% 7% 13% 11% 7% 8% 7% 7% 5% 14%	1330
	21st to end	Day	2 15% 9% 12% 11% 5% 10% 7% 6% 8% 16%	1093
December	1st to 10th	Day	6% 11% 7% 13% 13% 7% 9% 7% 9% 7% 10%	950
	11th to 20th	Day	2 9% 5% 14% 11% 7% 9% 7% 6% 10% 19%	1202
	21st to end	Day	3 12% 6% 14% 13% 6% 9% 8% 8% 9% 11%	1738
January	1st to 10th	Night	3 10% 7% 17% 16% 8% 9% 8% 7% 6% 8%	5261
	11th to 20th	Night	4 13% 6% 14% 9% 5% 6% 6% 5% 9% 23%	5016
	21st to end	Night	5% 21% 8% 12% 11% 5% 8% 7% 6% 6% 11%	5440
February	1st to 10th	Night	4 13% 7% 12% 9% 5% 8% 7% 7% 8% 20%	2632
	11th to 20th	Night	3 11% 7% 14% 11% 6% 9% 6% 7% 8% 20%	2447
	21st to end	Night	2 10% 6% 12% 10% 6% 7% 5% 6% 7% 29%	1921
March	1st to 10th	Night	2 10% 6% 9% 10% 6% 8% 5% 8% 8% 28%	2160
	11th to 20th	Night	1 11% 7% 13% 10% 5% 9% 9% 8% 9% 19%	2060
	21st to end	Night	3 12% 7% 13% 9% 5% 7% 6% 7% 8% 24%	2066
April	1st to 10th	Night	4 11% 8% 11% 9% 4 7% 6% 8% 8% 23%	1702
	11th to 20th	Night	5% 9% 6% 9% 10% 6% 8% 6% 8% 8% 24%	1601
	21st to end	Night	4 11% 4 9% 9% 6% 9% 7% 8% 7% 24%	1382
May	1st to 10th	Night	7% 14% 6% 8% 9% 5% 7% 7% 8% 6% 24%	1260
	11th to 20th	Night	5% 8% 4 7% 7% 4 7% 5% 8% 9% 36%	1195
	21st to end	Night	9% 8% 3 6% 5% 4 6% 8% 9% 10% 31%	1045
June	1st to 10th	Night	11% 10% 4 8% 7% 4 6% 6% 6% 10% 29%	900
	11th to 20th	Night	12% 9% 5% 8% 8% 4 8% 7% 8% 9% 21%	900
	21st to end	Night	14% 6% 3 8% 9% 5% 7% 8% 6% 9% 24%	900
July	1st to 10th	Night	12% 6% 3 8% 9% 4 7% 7% 7% 9% 28%	900
	11th to 20th	Night	13% 10% 4 9% 8% 5% 8% 7% 8% 9% 20%	1041
	21st to end	Night	15% 8% 4 7% 8% 4 7% 7% 6% 7% 29%	1200
August	1st to 10th	Night	14% 8% 3 5% 6% 4 6% 5% 8% 9% 33%	1253
	11th to 20th	Night	12% 7% 3 9% 9% 5% 6% 6% 7% 10% 25%	1399
	21st to end	Night	19% 10% 4 8% 8% 4 5% 5% 6% 5% 26%	1724
September	1st to 10th	Night	15% 11% 4 10% 8% 5% 7% 6% 6% 7% 21%	1656
	11th to 20th	Night	12% 11% 5% 8% 7% 5% 5% 7% 6% 7% 27%	1916
	21st to end	Night	13% 13% 6% 9% 8% 5% 7% 6% 6% 7% 21%	1980
October	1st to 10th	Night	9% 13% 4 9% 9% 5% 5% 6% 6% 8% 25%	2164
	11th to 20th	Night	9% 13% 6% 10% 9% 5% 8% 7% 6% 7% 20%	2340
	21st to end	Night	6% 13% 5% 10% 10% 6% 7% 7% 6% 8% 20%	2655
November	1st to 10th	Night	5% 15% 8% 14% 10% 6% 7% 6% 7% 7% 15%	2776
	11th to 20th	Night	4 15% 7% 14% 10% 7% 7% 8% 7% 7% 13%	2850
	21st to end	Night	3 15% 7% 14% 12% 6% 9% 7% 7% 8% 14%	3063
December	1st to 10th	Night	6% 13% 6% 11% 11% 7% 9% 9% 8% 8% 12%	3230
	11th to 20th	Night	3 13% 6% 12% 11% 6% 8% 7% 8% 8% 17%	3990
	21st to end	Night	2 10% 6% 12% 10% 7% 9% 9% 10% 9% 15%	5918

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% 7% 17% 7% 4 5%	1713
	11th to 20th	Day	56% 7% 8% 7% 11% 11%	1900
	21st to end	Day	64% 12% 13% 7% 4	2215
February	1st to 10th	Day	57% 9% 9% 13% 11% 1	1420
	11th to 20th	Day	58% 11% 14% 10% 6% 1	1408
	21st to end	Day	57% 6% 15% 15% 7% 1	1332
March	1st to 10th	Day	55% 7% 12% 16% 7% 2	1800
	11th to 20th	Day	60% 10% 14% 12% 3	1898
	21st to end	Day	58% 10% 17% 10% 5%	2290
April	1st to 10th	Day	65% 10% 13% 10% 3	2258
	11th to 20th	Day	63% 8% 11% 14% 4	2308
	21st to end	Day	64% 8% 14% 11% 2	2577
May	1st to 10th	Day	62% 10% 13% 13% 2	2700
	11th to 20th	Day	55% 8% 11% 17% 8% 1	2702
	21st to end	Day	53% 9% 14% 19% 4	3231
June	1st to 10th	Day	58% 9% 14% 15% 3	3060
	11th to 20th	Day	62% 9% 13% 11% 5%	3060
	21st to end	Day	61% 11% 15% 11% 2	3060
July	1st to 10th	Day	53% 14% 18% 14% 1	2976
	11th to 20th	Day	62% 12% 15% 11% 1	2827
	21st to end	Day	57% 12% 14% 14% 3	2943
August	1st to 10th	Day	51% 13% 18% 16% 2	2668
	11th to 20th	Day	62% 12% 14% 11% 1	2499
	21st to end	Day	65% 12% 12% 10% 1	2631
September	1st to 10th	Day	61% 11% 12% 13% 3	2301
	11th to 20th	Day	56% 11% 13% 17% 3	2044
	21st to end	Day	67% 12% 8% 11% 2	1980
October	1st to 10th	Day	55% 12% 17% 13% 3	1795
	11th to 20th	Day	62% 11% 12% 13% 1	1620
	21st to end	Day	60% 11% 14% 12% 3	1698
November	1st to 10th	Day	64% 11% 12% 10% 3	1302
	11th to 20th	Day	67% 10% 10% 9% 3	1330
	21st to end	Day	62% 10% 14% 8% 6%	1093
December	1st to 10th	Day	65% 11% 11% 10% 3	950
	11th to 20th	Day	54% 11% 14% 11% 8% 1	1204
	21st to end	Day	58% 11% 16% 7% 6% 2	1738
January	1st to 10th	Night	64% 7% 16% 7% 4 1	5261
	11th to 20th	Night	55% 7% 10% 9% 13% 7%	5060
	21st to end	Night	67% 13% 10% 8% 3	5440
February	1st to 10th	Night	57% 8% 10% 13% 10% 1	2632
	11th to 20th	Night	61% 9% 15% 8% 7% 1	2450
	21st to end	Night	54% 6% 15% 16% 7% 2	1921
March	1st to 10th	Night	52% 6% 12% 17% 11% 2	2160
	11th to 20th	Night	58% 10% 17% 11% 4	2061
	21st to end	Night	54% 10% 15% 15% 6%	2066
April	1st to 10th	Night	57% 10% 12% 17% 4	1702
	11th to 20th	Night	53% 12% 13% 14% 8%	1601
	21st to end	Night	55% 11% 16% 15% 2	1382
May	1st to 10th	Night	57% 12% 14% 14% 3	1260
	11th to 20th	Night	42% 11% 15% 23% 8% 1	1195
	21st to end	Night	45% 12% 16% 21% 6%	1045
June	1st to 10th	Night	51% 10% 13% 20% 6%	900
	11th to 20th	Night	55% 10% 15% 16% 5%	900
	21st to end	Night	54% 12% 18% 13% 2 1	900
July	1st to 10th	Night	48% 12% 21% 16% 3	875
	11th to 20th	Night	56% 13% 17% 13%	1008
	21st to end	Night	52% 13% 15% 17% 3	1133
August	1st to 10th	Night	46% 11% 21% 19% 3	1246
	11th to 20th	Night	54% 14% 16% 15% 2	1399
	21st to end	Night	61% 10% 16% 12% 2	1724
September	1st to 10th	Night	61% 11% 13% 11% 3	1656
	11th to 20th	Night	53% 12% 14% 17% 4	1916
	21st to end	Night	62% 10% 12% 13% 3	1980
October	1st to 10th	Night	55% 11% 14% 15% 5%	2164
	11th to 20th	Night	61% 11% 14% 13% 2	2340
	21st to end	Night	57% 10% 15% 14% 4	2655
November	1st to 10th	Night	63% 10% 12% 11% 3	2776
	11th to 20th	Night	66% 10% 13% 9% 3	2850
	21st to end	Night	63% 10% 13% 9% 4 1	3063
December	1st to 10th	Night	62% 11% 14% 10% 4	3230
	11th to 20th	Night	57% 9% 15% 13% 5% 1	3987
	21st to end	Night	54% 13% 16% 8% 9% 1	5918

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% 6% 24% 30% 21% 8%	180
	11th to 20th	Day	9% 12% 26% 29% 17% 8%	180
	21st to end	Day	9% 18% 21% 28% 20% 5%	198
February	1st to 10th	Day	14% 11% 30% 28% 13% 4	300
	11th to 20th	Day	12% 13% 25% 32% 13% 4	335
	21st to end	Day	9% 10% 36% 24% 16% 5%	280
March	1st to 10th	Day	9% 14% 34% 18% 18% 7%	340
	11th to 20th	Day	8% 15% 30% 30% 14% 3	384
	21st to end	Day	9% 16% 25% 23% 21% 5%	462
April	1st to 10th	Day	12% 14% 29% 29% 14% 3	420
	11th to 20th	Day	12% 13% 26% 28% 15% 5%	412
	21st to end	Day	15% 19% 28% 24% 12% 2	595
May	1st to 10th	Day	18% 16% 28% 24% 13% 1	603
	11th to 20th	Day	14% 12% 24% 29% 14% 6%	625
	21st to end	Day	15% 12% 23% 26% 17% 7%	799
June	1st to 10th	Day	21% 9% 22% 25% 18% 5%	810
	11th to 20th	Day	20% 8% 25% 24% 19% 4	810
	21st to end	Day	18% 10% 19% 24% 22% 8%	810
July	1st to 10th	Day	16% 9% 17% 27% 25% 7%	796
	11th to 20th	Day	22% 10% 23% 23% 20% 3	652
	21st to end	Day	20% 8% 22% 20% 21% 8%	684
August	1st to 10th	Day	16% 11% 21% 24% 19% 8%	626
	11th to 20th	Day	26% 18% 25% 16% 12% 3	615
	21st to end	Day	28% 12% 20% 20% 15% 5%	552
September	1st to 10th	Day	24% 14% 26% 22% 12% 3	450
	11th to 20th	Day	22% 15% 22% 21% 16% 5%	450
	21st to end	Day	30% 16% 25% 21% 6% 3	450
October	1st to 10th	Day	20% 16% 22% 24% 16% 1	407
	11th to 20th	Day	19% 18% 29% 23% 9% 2	360
	21st to end	Day	14% 13% 27% 27% 16% 4	314
November	1st to 10th	Day	14% 14% 34% 21% 14% 3	180
	11th to 20th	Day	9% 11% 31% 22% 23% 4	180
	21st to end	Day	12% 14% 24% 27% 22% 1	180
December	1st to 10th	Day	4 12% 28% 29% 22% 4	180
	11th to 20th	Day	8% 11% 22% 32% 19% 7%	180
	21st to end	Day	6% 9% 20% 33% 24% 8%	198
January	1st to 10th	Night	8% 8% 27% 37% 17% 3	974
	11th to 20th	Night	12% 11% 29% 31% 14% 3	850
	21st to end	Night	13% 15% 25% 27% 17% 3	935
February	1st to 10th	Night	14% 8% 28% 32% 16% 2	822
	11th to 20th	Night	8% 10% 29% 34% 15% 4	784
	21st to end	Night	7% 9% 24% 36% 21% 5%	600
March	1st to 10th	Night	7% 13% 26% 31% 18% 5%	720
	11th to 20th	Night	6% 11% 28% 37% 16% 2	720
	21st to end	Night	7% 9% 23% 28% 26% 7%	680
April	1st to 10th	Night	9% 9% 22% 29% 26% 6%	540
	11th to 20th	Night	7% 8% 23% 34% 25% 4	533
	21st to end	Night	8% 7% 24% 35% 22% 4	478
May	1st to 10th	Night	13% 10% 20% 33% 20% 4	360
	11th to 20th	Night	8% 5% 17% 34% 32% 4	354
	21st to end	Night	11% 6% 17% 33% 28% 6%	389
June	1st to 10th	Night	15% 7% 21% 27% 25% 5%	360
	11th to 20th	Night	17% 6% 19% 28% 26% 3	360
	21st to end	Night	14% 7% 22% 28% 26% 3	360
July	1st to 10th	Night	16% 5% 15% 34% 27% 4	350
	11th to 20th	Night	17% 7% 16% 32% 26% 3	348
	21st to end	Night	15% 6% 21% 24% 29% 6%	394
August	1st to 10th	Night	17% 7% 17% 23% 30% 5%	358
	11th to 20th	Night	17% 8% 20% 28% 23% 4	509
	21st to end	Night	25% 7% 18% 21% 25% 4	594
September	1st to 10th	Night	24% 9% 19% 28% 17% 3	540
	11th to 20th	Night	20% 10% 17% 26% 23% 4	656
	21st to end	Night	23% 13% 27% 22% 13% 2	720
October	1st to 10th	Night	19% 12% 20% 30% 16% 2	720
	11th to 20th	Night	18% 14% 27% 26% 14% 2	720
	21st to end	Night	17% 11% 23% 32% 13% 3	792
November	1st to 10th	Night	16% 10% 28% 29% 15% 3	830
	11th to 20th	Night	13% 8% 26% 33% 16% 4	850
	21st to end	Night	13% 12% 27% 32% 14% 2	983
December	1st to 10th	Night	12% 10% 23% 37% 16% 2	1040
	11th to 20th	Night	9% 9% 23% 37% 18% 3	1040
	21st to end	Night	7% 10% 24% 33% 21% 4	1144

Page generated at 2024-02-02 02:20:33. Version ac07

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