Wesley Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wesley Creek clear sky chart from 2005-11-06 to 2024-01-17.

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% 4 7% 7% 4 6% 6% 7% 8% 32%	74587
	Night	8% 10% 4 8% 7% 4 6% 6% 6% 8% 32%	75241
Transparency	Day	47% 7% 18% 21% 6%	74246
	Night	48% 7% 16% 21% 7% 1	75100
Seeing	Day	14% 7% 23% 29% 20% 7%	15443
	Night	14% 5% 23% 37% 19% 2	23706

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	6% 14% 5% 13% 11% 5% 7% 6% 6% 7% 21%	1139
	11th to 20th	Day	10% 16% 5% 6% 9% 5% 6% 6% 6% 6% 25%	1116
	21st to end	Day	8% 12% 6% 11% 9% 7% 6% 6% 5% 7% 24%	1404
February	1st to 10th	Day	7% 13% 5% 9% 9% 3 8% 10% 8% 10% 20%	1440
	11th to 20th	Day	6% 10% 6% 11% 9% 6% 7% 7% 9% 8% 23%	1400
	21st to end	Day	5% 9% 5% 12% 9% 5% 8% 8% 6% 10% 22%	1416
March	1st to 10th	Day	5% 11% 5% 9% 7% 5% 7% 6% 8% 8% 29%	1800
	11th to 20th	Day	6% 12% 5% 10% 7% 4 5% 6% 5% 8% 31%	1847
	21st to end	Day	7% 14% 5% 8% 7% 4 6% 6% 6% 9% 28%	2353
April	1st to 10th	Day	5% 9% 4 7% 7% 5% 7% 5% 7% 8% 35%	2176
	11th to 20th	Day	8% 10% 4 7% 8% 4 5% 5% 7% 9% 32%	2318
	21st to end	Day	11% 10% 5% 7% 8% 5% 6% 5% 5% 8% 30%	2520
May	1st to 10th	Day	10% 9% 3 7% 5% 4 6% 6% 6% 8% 35%	2627
	11th to 20th	Day	9% 7% 4 5% 5% 3 5% 5% 7% 9% 40%	2654
	21st to end	Day	14% 6% 4 6% 5% 4 5% 5% 6% 8% 36%	3110
June	1st to 10th	Day	13% 7% 3 7% 7% 4 5% 5% 7% 7% 36%	2880
	11th to 20th	Day	20% 8% 4 8% 6% 4 6% 6% 6% 6% 25%	2880
	21st to end	Day	10% 6% 3 6% 7% 4 7% 6% 8% 9% 36%	2880
July	1st to 10th	Day	13% 6% 3 5% 5% 3 5% 6% 7% 9% 36%	2880
	11th to 20th	Day	11% 6% 3 6% 6% 4 6% 6% 8% 10% 34%	2880
	21st to end	Day	11% 6% 3 6% 5% 3 5% 5% 7% 8% 42%	3085
August	1st to 10th	Day	11% 6% 2 5% 6% 4 6% 7% 7% 10% 35%	2547
	11th to 20th	Day	9% 5% 3 7% 5% 4 5% 6% 6% 9% 41%	2475
	21st to end	Day	13% 6% 3 6% 6% 4 6% 6% 7% 8% 35%	2646
September	1st to 10th	Day	14% 6% 3 6% 5% 3 4 5% 6% 9% 39%	2196
	11th to 20th	Day	10% 7% 3 6% 6% 4 6% 6% 6% 9% 39%	2088
	21st to end	Day	9% 7% 3 6% 6% 3 5% 6% 7% 9% 39%	1980
October	1st to 10th	Day	12% 10% 3 7% 6% 4 5% 6% 6% 7% 33%	1817
	11th to 20th	Day	12% 11% 4 9% 7% 3 6% 5% 6% 7% 30%	1620
	21st to end	Day	12% 12% 6% 9% 8% 4 5% 5% 5% 7% 27%	1778
November	1st to 10th	Day	10% 12% 6% 10% 8% 4 7% 7% 6% 7% 24%	1326
	11th to 20th	Day	8% 11% 6% 12% 8% 4 8% 7% 6% 10% 21%	1330
	21st to end	Day	7% 14% 7% 9% 9% 5% 5% 5% 6% 8% 26%	1307
December	1st to 10th	Day	7% 13% 5% 11% 9% 5% 8% 6% 6% 7% 24%	1140
	11th to 20th	Day	11% 10% 4 9% 11% 6% 7% 7% 5% 9% 21%	1442
	21st to end	Day	3 8% 4 7% 7% 5% 6% 6% 6% 9% 38%	2090
January	1st to 10th	Night	7% 12% 6% 11% 10% 5% 7% 6% 7% 7% 21%	3026
	11th to 20th	Night	9% 13% 6% 11% 7% 5% 6% 6% 6% 7% 24%	2989
	21st to end	Night	10% 14% 6% 11% 10% 4 5% 5% 6% 7% 22%	2967
February	1st to 10th	Night	7% 11% 6% 11% 8% 4 6% 6% 6% 8% 27%	2520
	11th to 20th	Night	6% 13% 6% 12% 9% 5% 6% 6% 5% 7% 26%	2446
	21st to end	Night	3 9% 5% 10% 7% 5% 7% 7% 8% 9% 31%	1840
March	1st to 10th	Night	6% 9% 4 8% 6% 5% 6% 5% 8% 8% 35%	2160
	11th to 20th	Night	7% 12% 4 8% 7% 4 5% 6% 6% 9% 30%	2112
	21st to end	Night	7% 13% 4 9% 6% 4 6% 5% 6% 8% 33%	1999
April	1st to 10th	Night	6% 9% 4 8% 7% 4 5% 5% 7% 8% 36%	1784
	11th to 20th	Night	8% 10% 4 8% 6% 4 6% 6% 6% 10% 32%	1589
	21st to end	Night	11% 11% 4 8% 7% 5% 6% 6% 6% 8% 29%	1440
May	1st to 10th	Night	10% 8% 3 7% 6% 4 7% 6% 6% 9% 35%	1332
	11th to 20th	Night	8% 6% 3 6% 5% 5% 5% 5% 6% 7% 44%	1239
	21st to end	Night	14% 6% 3 6% 5% 3 5% 5% 7% 8% 36%	1164
June	1st to 10th	Night	11% 6% 3 6% 7% 5% 6% 7% 5% 8% 35%	1080
	11th to 20th	Night	17% 8% 4 7% 6% 4 5% 5% 6% 9% 29%	1080
	21st to end	Night	9% 5% 3 6% 6% 4 5% 6% 7% 9% 40%	1080
July	1st to 10th	Night	13% 6% 3 5% 6% 3 5% 5% 6% 9% 41%	1080
	11th to 20th	Night	9% 6% 4 6% 6% 4 6% 6% 8% 11% 33%	1080
	21st to end	Night	12% 3 2 4 4 4 5% 6% 9% 9% 42%	1231
August	1st to 10th	Night	7% 6% 3 5% 6% 4 6% 6% 7% 9% 42%	1390
	11th to 20th	Night	6% 4 2 5% 6% 3 6% 6% 7% 9% 45%	1424
	21st to end	Night	13% 6% 3 6% 4 3 5% 5% 8% 9% 39%	1709
September	1st to 10th	Night	13% 7% 3 6% 5% 4 5% 5% 6% 8% 38%	1763
	11th to 20th	Night	9% 6% 2 6% 6% 4 6% 5% 6% 8% 41%	1872
	21st to end	Night	9% 8% 3 6% 6% 3 5% 5% 6% 8% 42%	1980
October	1st to 10th	Night	10% 9% 4 8% 8% 3 5% 5% 6% 7% 35%	2139
	11th to 20th	Night	9% 9% 3 8% 6% 4 5% 5% 6% 8% 36%	2340
	21st to end	Night	11% 14% 4 9% 7% 4 5% 5% 5% 6% 30%	2577
November	1st to 10th	Night	11% 13% 5% 10% 7% 4 5% 5% 5% 6% 27%	2732
	11th to 20th	Night	9% 13% 6% 10% 8% 5% 7% 6% 6% 7% 23%	2850
	21st to end	Night	7% 13% 6% 10% 10% 4 6% 5% 6% 7% 26%	2871
December	1st to 10th	Night	8% 11% 6% 11% 10% 5% 7% 6% 6% 7% 24%	3040
	11th to 20th	Night	9% 15% 5% 9% 9% 4 5% 6% 7% 7% 24%	3750
	21st to end	Night	3 8% 4 8% 8% 5% 6% 6% 6% 9% 37%	5566

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% 14% 13% 6%	1139
	11th to 20th	Day	59% 5% 14% 15% 5% 2	1116
	21st to end	Day	59% 7% 15% 14% 4	1404
February	1st to 10th	Day	54% 8% 16% 14% 8%	1440
	11th to 20th	Day	55% 7% 18% 16% 4	1408
	21st to end	Day	54% 7% 15% 15% 8%	1416
March	1st to 10th	Day	48% 7% 21% 18% 6%	1800
	11th to 20th	Day	50% 7% 16% 22% 5%	1847
	21st to end	Day	52% 8% 18% 18% 5%	2353
April	1st to 10th	Day	45% 6% 17% 24% 8%	2176
	11th to 20th	Day	47% 5% 15% 24% 8% 2	2318
	21st to end	Day	51% 6% 14% 22% 7%	2520
May	1st to 10th	Day	44% 6% 15% 23% 10% 1	2627
	11th to 20th	Day	39% 5% 14% 26% 14% 2	2658
	21st to end	Day	45% 5% 14% 23% 12% 1	3111
June	1st to 10th	Day	45% 5% 16% 26% 8% 1	2880
	11th to 20th	Day	57% 7% 14% 17% 5%	2880
	21st to end	Day	43% 6% 19% 24% 7%	2880
July	1st to 10th	Day	41% 7% 21% 24% 6% 1	2801
	11th to 20th	Day	43% 9% 27% 19% 2	2793
	21st to end	Day	38% 7% 26% 24% 4	2913
August	1st to 10th	Day	41% 9% 28% 19% 3	2529
	11th to 20th	Day	38% 7% 24% 25% 5%	2475
	21st to end	Day	43% 8% 22% 22% 4	2646
September	1st to 10th	Day	42% 6% 25% 22% 4	2196
	11th to 20th	Day	40% 6% 25% 25% 4	2088
	21st to end	Day	40% 7% 22% 24% 8%	1980
October	1st to 10th	Day	48% 7% 18% 22% 6%	1817
	11th to 20th	Day	52% 5% 18% 20% 4	1620
	21st to end	Day	56% 7% 17% 16% 4	1778
November	1st to 10th	Day	56% 8% 14% 20% 3	1326
	11th to 20th	Day	56% 9% 17% 15% 3	1330
	21st to end	Day	54% 7% 16% 18% 4 1	1307
December	1st to 10th	Day	58% 5% 12% 15% 9% 1	1140
	11th to 20th	Day	58% 9% 12% 17% 3	1444
	21st to end	Day	40% 7% 15% 26% 9% 2	2090
January	1st to 10th	Night	59% 8% 14% 13% 6% 1	3026
	11th to 20th	Night	56% 8% 16% 13% 5% 1	2989
	21st to end	Night	61% 6% 13% 12% 7% 1	2967
February	1st to 10th	Night	54% 5% 15% 18% 8% 1	2520
	11th to 20th	Night	57% 6% 15% 17% 5%	2448
	21st to end	Night	45% 6% 20% 21% 8%	1840
March	1st to 10th	Night	43% 6% 18% 24% 8%	2160
	11th to 20th	Night	48% 7% 13% 25% 7%	2113
	21st to end	Night	48% 5% 16% 24% 7%	1999
April	1st to 10th	Night	44% 6% 11% 25% 13% 1	1784
	11th to 20th	Night	46% 6% 13% 22% 11% 1	1589
	21st to end	Night	51% 6% 11% 22% 10%	1440
May	1st to 10th	Night	45% 5% 12% 25% 12% 1	1332
	11th to 20th	Night	38% 6% 11% 25% 18% 3	1239
	21st to end	Night	43% 5% 13% 24% 12% 2	1164
June	1st to 10th	Night	45% 5% 13% 26% 10% 1	1080
	11th to 20th	Night	52% 6% 14% 22% 6%	1080
	21st to end	Night	37% 8% 19% 26% 9% 1	1080
July	1st to 10th	Night	38% 6% 20% 28% 8%	1050
	11th to 20th	Night	42% 7% 26% 22% 3	1044
	21st to end	Night	34% 8% 28% 25% 5% 1	1163
August	1st to 10th	Night	36% 9% 26% 25% 5%	1383
	11th to 20th	Night	32% 8% 25% 28% 7% 1	1424
	21st to end	Night	39% 6% 21% 25% 7% 1	1709
September	1st to 10th	Night	41% 8% 20% 23% 7% 1	1763
	11th to 20th	Night	39% 6% 21% 26% 8%	1872
	21st to end	Night	40% 7% 17% 27% 9% 1	1980
October	1st to 10th	Night	47% 6% 16% 22% 9% 1	2139
	11th to 20th	Night	44% 8% 18% 24% 5%	2340
	21st to end	Night	53% 6% 15% 19% 6%	2577
November	1st to 10th	Night	56% 7% 13% 21% 3	2732
	11th to 20th	Night	58% 8% 14% 16% 4	2850
	21st to end	Night	55% 8% 18% 15% 3 1	2871
December	1st to 10th	Night	58% 7% 12% 15% 8% 1	3040
	11th to 20th	Night	56% 8% 13% 17% 5%	3747
	21st to end	Night	41% 6% 19% 26% 7% 1	5566

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% 25% 33% 22% 4	180
	11th to 20th	Day	17% 6% 23% 31% 20% 3	172
	21st to end	Day	14% 2 26% 33% 22% 3	176
February	1st to 10th	Day	12% 6% 29% 33% 14% 6%	160
	11th to 20th	Day	13% 5% 28% 30% 17% 8%	160
	21st to end	Day	9% 4 29% 32% 20% 6%	306
March	1st to 10th	Day	8% 7% 23% 32% 22% 7%	420
	11th to 20th	Day	10% 3 29% 31% 22% 4	420
	21st to end	Day	16% 5% 27% 29% 17% 6%	462
April	1st to 10th	Day	10% 6% 25% 32% 19% 8%	420
	11th to 20th	Day	14% 9% 27% 22% 21% 7%	412
	21st to end	Day	16% 11% 27% 26% 15% 5%	420
May	1st to 10th	Day	13% 10% 27% 27% 19% 5%	530
	11th to 20th	Day	11% 8% 18% 35% 20% 8%	625
	21st to end	Day	16% 5% 17% 30% 25% 7%	873
June	1st to 10th	Day	15% 8% 25% 28% 21% 4	810
	11th to 20th	Day	22% 7% 17% 28% 20% 6%	810
	21st to end	Day	12% 6% 18% 28% 26% 11%	810
July	1st to 10th	Day	14% 5% 18% 30% 25% 8%	796
	11th to 20th	Day	12% 5% 16% 30% 28% 9%	792
	21st to end	Day	14% 4 18% 32% 22% 10%	831
August	1st to 10th	Day	15% 7% 16% 23% 25% 15%	487
	11th to 20th	Day	11% 10% 28% 29% 18% 5%	437
	21st to end	Day	17% 7% 27% 25% 16% 7%	495
September	1st to 10th	Day	18% 5% 24% 28% 17% 7%	450
	11th to 20th	Day	15% 8% 22% 30% 18% 6%	450
	21st to end	Day	10% 12% 30% 27% 17% 4	450
October	1st to 10th	Day	17% 11% 23% 31% 16% 4	426
	11th to 20th	Day	18% 6% 25% 30% 17% 4	270
	21st to end	Day	20% 7% 27% 29% 14% 3	295
November	1st to 10th	Day	14% 5% 34% 27% 16% 4	180
	11th to 20th	Day	14% 4 34% 28% 16% 3	180
	21st to end	Day	11% 8% 34% 31% 16% 1	180
December	1st to 10th	Day	6% 7% 29% 37% 16% 6%	180
	11th to 20th	Day	11% 8% 25% 37% 17% 2	180
	21st to end	Day	8% 4 21% 41% 22% 5%	198
January	1st to 10th	Night	13% 4 27% 39% 15% 2	1040
	11th to 20th	Night	14% 5% 28% 36% 16% 1	1021
	21st to end	Night	18% 8% 27% 34% 11% 2	930
February	1st to 10th	Night	12% 4 26% 35% 20% 3	720
	11th to 20th	Night	13% 4 24% 41% 17% 2	704
	21st to end	Night	5% 4 27% 40% 20% 4	592
March	1st to 10th	Night	10% 5% 26% 34% 22% 4	720
	11th to 20th	Night	13% 4 22% 42% 17% 1	720
	21st to end	Night	14% 5% 19% 36% 24% 2	792
April	1st to 10th	Night	10% 6% 21% 40% 21% 2	704
	11th to 20th	Night	13% 4 24% 33% 23% 3	521
	21st to end	Night	17% 3 25% 38% 16% 2	360
May	1st to 10th	Night	13% 6% 17% 38% 24% 2	360
	11th to 20th	Night	9% 6% 24% 34% 24% 2	354
	21st to end	Night	17% 3 12% 39% 27% 2	389
June	1st to 10th	Night	13% 5% 14% 40% 28%	360
	11th to 20th	Night	20% 4 13% 35% 24% 4	360
	21st to end	Night	11% 3 16% 38% 28% 4	360
July	1st to 10th	Night	14% 3 14% 37% 30% 3	350
	11th to 20th	Night	12% 3 9% 39% 34% 3	348
	21st to end	Night	13% 2 13% 35% 34% 3	394
August	1st to 10th	Night	9% 3 7% 35% 38% 6%	358
	11th to 20th	Night	7% 2 20% 46% 22% 3	356
	21st to end	Night	17% 2 15% 40% 23% 3	521
September	1st to 10th	Night	18% 2 15% 36% 26% 3	683
	11th to 20th	Night	11% 3 18% 41% 24% 3	720
	21st to end	Night	12% 8% 27% 33% 16% 3	720
October	1st to 10th	Night	17% 7% 23% 36% 17% 2	720
	11th to 20th	Night	14% 6% 25% 37% 17% 3	720
	21st to end	Night	19% 9% 20% 36% 14% 2	792
November	1st to 10th	Night	18% 7% 24% 35% 15% 2	882
	11th to 20th	Night	15% 8% 27% 38% 11% 1	950
	21st to end	Night	13% 7% 31% 37% 10% 1	961
December	1st to 10th	Night	14% 6% 29% 35% 12% 3	1040
	11th to 20th	Night	15% 6% 27% 37% 13% 2	1040
	21st to end	Night	12% 4 25% 36% 20% 3	1144

Page generated at 2024-01-14 07:55:02. Version ac07

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