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 2025-01-07.

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	9% 9% 3 9% 6% 6% 5% 5% 7% 8% 34%	108729
	Night	8% 10% 4 10% 6% 6% 6% 5% 7% 8% 31%	108873
Transparency	Day	46% 6% 18% 23% 7%	108448
	Night	49% 6% 16% 21% 7% 1	108800
Seeing	Day	14% 7% 23% 30% 20% 6%	16793
	Night	14% 5% 23% 37% 19% 2	24977

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% 15% 6% 16% 11% 11% 6% 4 6% 6% 14%	1935
	11th to 20th	Day	6% 13% 4 10% 9% 7% 5% 6% 7% 6% 27%	1882
	21st to end	Day	6% 11% 5% 10% 10% 7% 5% 5% 6% 7% 28%	2460
February	1st to 10th	Day	7% 14% 4 11% 8% 5% 9% 6% 8% 9% 20%	1520
	11th to 20th	Day	5% 10% 5% 11% 8% 6% 7% 5% 9% 7% 26%	1480
	21st to end	Day	4 11% 5% 13% 8% 8% 7% 6% 7% 10% 22%	1501
March	1st to 10th	Day	3 8% 4 12% 8% 7% 7% 5% 7% 8% 32%	3138
	11th to 20th	Day	4 9% 4 10% 6% 5% 6% 6% 7% 9% 34%	3266
	21st to end	Day	4 10% 4 13% 7% 6% 6% 5% 6% 8% 31%	4129
April	1st to 10th	Day	5% 10% 3 8% 7% 7% 5% 4 7% 8% 35%	2297
	11th to 20th	Day	7% 11% 3 8% 7% 6% 5% 4 7% 9% 34%	2449
	21st to end	Day	11% 12% 4 9% 7% 6% 6% 4 6% 7% 30%	2660
May	1st to 10th	Day	10% 9% 3 7% 5% 5% 5% 4 6% 8% 38%	4611
	11th to 20th	Day	10% 10% 4 7% 6% 5% 5% 5% 7% 8% 34%	4694
	21st to end	Day	12% 8% 3 8% 5% 6% 6% 5% 8% 9% 29%	5508
June	1st to 10th	Day	13% 8% 3 8% 6% 5% 5% 4 7% 7% 35%	3040
	11th to 20th	Day	20% 9% 4 9% 6% 6% 6% 4 6% 6% 25%	3040
	21st to end	Day	10% 7% 3 7% 6% 5% 6% 4 8% 8% 36%	3040
July	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 7% 9% 45%	5060
	11th to 20th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 9% 43%	5060
	21st to end	Day	15% 6% 2 5% 4 4 4 3 6% 9% 42%	5397
August	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 44%	4469
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 4 6% 8% 39%	4330
	21st to end	Day	13% 6% 3 8% 5% 5% 4 4 7% 7% 38%	4645
September	1st to 10th	Day	14% 6% 2 7% 4 4 4 4 6% 8% 39%	2317
	11th to 20th	Day	9% 7% 2 7% 5% 5% 6% 5% 6% 9% 39%	2204
	21st to end	Day	9% 7% 3 7% 4 4 6% 5% 7% 9% 39%	2090
October	1st to 10th	Day	12% 9% 3 8% 5% 5% 5% 5% 6% 8% 33%	3195
	11th to 20th	Day	12% 10% 3 9% 5% 4 5% 4 6% 7% 34%	2842
	21st to end	Day	9% 14% 5% 10% 5% 4 4 3 6% 8% 31%	3084
November	1st to 10th	Day	9% 13% 6% 11% 7% 5% 7% 5% 6% 7% 24%	1397
	11th to 20th	Day	7% 13% 5% 13% 7% 7% 7% 6% 6% 9% 21%	1400
	21st to end	Day	6% 15% 6% 11% 9% 5% 5% 4 6% 7% 25%	1375
December	1st to 10th	Day	10% 15% 5% 16% 9% 8% 7% 5% 5% 5% 15%	1960
	11th to 20th	Day	9% 14% 5% 10% 10% 8% 7% 6% 6% 9% 17%	2262
	21st to end	Day	2 9% 4 14% 10% 6% 5% 4 5% 7% 33%	2992
January	1st to 10th	Night	5% 14% 8% 19% 9% 6% 6% 4 6% 6% 17%	5143
	11th to 20th	Night	6% 12% 4 10% 6% 6% 8% 6% 9% 7% 27%	5016
	21st to end	Night	9% 14% 5% 12% 8% 6% 6% 5% 6% 7% 22%	5225
February	1st to 10th	Night	7% 12% 5% 12% 7% 6% 6% 5% 6% 8% 27%	2660
	11th to 20th	Night	6% 13% 5% 13% 8% 6% 6% 4 5% 7% 27%	2586
	21st to end	Night	3 10% 4 11% 7% 6% 6% 5% 8% 9% 31%	1952
March	1st to 10th	Night	3 8% 4 11% 8% 7% 7% 5% 8% 8% 32%	3736
	11th to 20th	Night	4 9% 3 8% 6% 6% 6% 5% 8% 11% 33%	3713
	21st to end	Night	4 10% 4 13% 6% 6% 6% 4 6% 7% 35%	3520
April	1st to 10th	Night	6% 11% 4 9% 6% 5% 5% 4 7% 8% 36%	1883
	11th to 20th	Night	8% 12% 3 10% 4 5% 5% 5% 7% 9% 32%	1678
	21st to end	Night	11% 12% 4 8% 6% 6% 5% 5% 6% 7% 29%	1520
May	1st to 10th	Night	8% 8% 3 9% 6% 5% 5% 4 5% 7% 39%	2348
	11th to 20th	Night	8% 8% 3 9% 6% 6% 6% 5% 7% 7% 34%	2199
	21st to end	Night	12% 8% 3 7% 6% 5% 5% 5% 7% 9% 33%	2066
June	1st to 10th	Night	11% 8% 3 7% 6% 7% 5% 6% 5% 7% 34%	1140
	11th to 20th	Night	17% 9% 3 8% 5% 6% 5% 4 6% 10% 28%	1140
	21st to end	Night	10% 5% 3 7% 5% 5% 5% 5% 8% 9% 39%	1140
July	1st to 10th	Night	12% 5% 2 5% 5% 4 4 4 6% 8% 44%	1900
	11th to 20th	Night	7% 6% 3 7% 6% 5% 6% 5% 8% 10% 37%	1900
	21st to end	Night	12% 5% 2 5% 3 5% 5% 4 8% 9% 42%	2154
August	1st to 10th	Night	9% 6% 2 6% 4 4 5% 4 6% 7% 46%	2459
	11th to 20th	Night	10% 6% 2 6% 4 4 5% 4 5% 7% 45%	2497
	21st to end	Night	13% 5% 2 6% 4 5% 5% 5% 8% 9% 38%	3017
September	1st to 10th	Night	13% 7% 3 7% 4 5% 5% 4 6% 8% 39%	1861
	11th to 20th	Night	9% 7% 2 7% 5% 5% 5% 4 6% 9% 41%	1976
	21st to end	Night	9% 9% 2 7% 5% 4 5% 4 6% 8% 41%	2090
October	1st to 10th	Night	9% 10% 4 8% 6% 5% 5% 4 6% 7% 35%	3779
	11th to 20th	Night	8% 8% 3 8% 5% 5% 5% 5% 7% 9% 39%	4086
	21st to end	Night	8% 12% 4 9% 6% 6% 6% 4 6% 7% 31%	4472
November	1st to 10th	Night	11% 14% 5% 11% 6% 6% 5% 4 6% 6% 27%	2880
	11th to 20th	Night	9% 14% 5% 12% 7% 7% 6% 5% 6% 6% 23%	3000
	21st to end	Night	6% 14% 5% 13% 8% 6% 5% 4 6% 7% 25%	3023
December	1st to 10th	Night	11% 14% 5% 14% 8% 6% 6% 4 6% 7% 19%	5220
	11th to 20th	Night	8% 16% 6% 12% 7% 6% 5% 5% 7% 7% 20%	5930
	21st to end	Night	3 9% 5% 13% 9% 7% 6% 4 6% 8% 31%	7964

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	69% 6% 12% 10% 3	1935
	11th to 20th	Day	54% 5% 10% 14% 15% 2	1900
	21st to end	Day	51% 9% 20% 15% 4	2460
February	1st to 10th	Day	55% 7% 15% 14% 9%	1520
	11th to 20th	Day	52% 7% 18% 17% 6%	1488
	21st to end	Day	54% 8% 15% 16% 7%	1501
March	1st to 10th	Day	47% 6% 19% 24% 4	3138
	11th to 20th	Day	41% 11% 21% 22% 6%	3266
	21st to end	Day	48% 8% 15% 22% 8%	4129
April	1st to 10th	Day	44% 6% 17% 24% 9%	2297
	11th to 20th	Day	46% 5% 14% 24% 10% 2	2449
	21st to end	Day	51% 6% 13% 22% 7%	2660
May	1st to 10th	Day	40% 8% 12% 26% 14% 1	4611
	11th to 20th	Day	44% 6% 13% 25% 10% 1	4698
	21st to end	Day	46% 7% 16% 22% 9% 1	5509
June	1st to 10th	Day	46% 5% 15% 25% 8% 1	3040
	11th to 20th	Day	57% 7% 13% 18% 5%	3040
	21st to end	Day	43% 6% 19% 24% 8%	3040
July	1st to 10th	Day	35% 4 23% 29% 8%	4981
	11th to 20th	Day	36% 5% 19% 29% 11% 1	4973
	21st to end	Day	40% 4 24% 25% 7%	5226
August	1st to 10th	Day	38% 5% 21% 33% 3	4451
	11th to 20th	Day	43% 5% 18% 24% 10%	4372
	21st to end	Day	44% 5% 27% 22% 3	4644
September	1st to 10th	Day	42% 6% 25% 23% 4	2317
	11th to 20th	Day	40% 6% 24% 25% 4	2204
	21st to end	Day	41% 6% 21% 23% 9%	2090
October	1st to 10th	Day	47% 4 21% 23% 5%	3195
	11th to 20th	Day	49% 3 17% 27% 3	2842
	21st to end	Day	52% 4 23% 19% 3	3084
November	1st to 10th	Day	56% 8% 14% 19% 3	1397
	11th to 20th	Day	57% 8% 17% 15% 3	1400
	21st to end	Day	56% 6% 16% 17% 4 1	1375
December	1st to 10th	Day	71% 5% 10% 9% 5%	1960
	11th to 20th	Day	61% 6% 16% 14% 3	2264
	21st to end	Day	49% 5% 14% 24% 6% 1	2992
January	1st to 10th	Night	65% 7% 11% 12% 5%	5143
	11th to 20th	Night	50% 8% 11% 12% 17% 1	5060
	21st to end	Night	57% 9% 18% 12% 4 1	5225
February	1st to 10th	Night	54% 5% 15% 18% 8% 1	2660
	11th to 20th	Night	55% 6% 15% 17% 6% 1	2588
	21st to end	Night	46% 6% 19% 21% 8%	1952
March	1st to 10th	Night	46% 6% 17% 24% 8%	3736
	11th to 20th	Night	40% 9% 21% 24% 6%	3714
	21st to end	Night	44% 9% 12% 26% 9%	3520
April	1st to 10th	Night	44% 6% 11% 25% 13% 1	1883
	11th to 20th	Night	46% 6% 13% 21% 13% 1	1678
	21st to end	Night	51% 6% 11% 22% 10% 1	1520
May	1st to 10th	Night	42% 6% 12% 24% 15% 1	2348
	11th to 20th	Night	42% 8% 11% 24% 13% 2	2199
	21st to end	Night	41% 8% 15% 27% 7% 1	2066
June	1st to 10th	Night	47% 5% 12% 25% 10% 1	1140
	11th to 20th	Night	52% 5% 14% 23% 6%	1140
	21st to end	Night	38% 7% 19% 25% 10% 1	1140
July	1st to 10th	Night	38% 4 17% 29% 12%	1870
	11th to 20th	Night	41% 4 17% 25% 11% 2	1864
	21st to end	Night	37% 5% 25% 25% 8% 1	2086
August	1st to 10th	Night	37% 5% 17% 37% 3	2452
	11th to 20th	Night	37% 5% 19% 24% 14%	2521
	21st to end	Night	41% 4 29% 22% 4	3017
September	1st to 10th	Night	40% 8% 20% 24% 7% 1	1861
	11th to 20th	Night	39% 6% 21% 27% 7%	1976
	21st to end	Night	41% 7% 17% 26% 9%	2090
October	1st to 10th	Night	47% 4 19% 21% 9%	3779
	11th to 20th	Night	41% 4 19% 30% 6%	4086
	21st to end	Night	51% 4 20% 21% 4	4472
November	1st to 10th	Night	56% 6% 14% 21% 3	2880
	11th to 20th	Night	59% 7% 14% 16% 3	3000
	21st to end	Night	56% 7% 17% 15% 3 1	3023
December	1st to 10th	Night	64% 5% 11% 14% 5%	5220
	11th to 20th	Night	61% 5% 16% 14% 3	5927
	21st to end	Night	50% 4 17% 23% 5%	7964

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% 5% 24% 32% 21% 6%	192
	11th to 20th	Day	17% 6% 21% 32% 20% 4	180
	21st to end	Day	13% 3 27% 33% 21% 3	198
February	1st to 10th	Day	11% 6% 30% 31% 16% 7%	180
	11th to 20th	Day	11% 4 26% 32% 19% 8%	180
	21st to end	Day	9% 5% 30% 31% 19% 6%	337
March	1st to 10th	Day	8% 8% 24% 33% 21% 6%	460
	11th to 20th	Day	9% 5% 29% 30% 23% 4	460
	21st to end	Day	15% 5% 26% 31% 18% 6%	506
April	1st to 10th	Day	9% 8% 27% 31% 18% 7%	460
	11th to 20th	Day	13% 9% 27% 24% 20% 8%	452
	21st to end	Day	17% 10% 26% 27% 15% 5%	460
May	1st to 10th	Day	13% 9% 28% 26% 19% 5%	576
	11th to 20th	Day	12% 8% 18% 35% 20% 8%	675
	21st to end	Day	15% 6% 18% 30% 25% 7%	939
June	1st to 10th	Day	16% 8% 25% 27% 21% 3	870
	11th to 20th	Day	23% 7% 17% 28% 20% 6%	870
	21st to end	Day	12% 6% 17% 28% 27% 11%	870
July	1st to 10th	Day	14% 4 17% 30% 27% 7%	856
	11th to 20th	Day	12% 5% 16% 29% 28% 10%	852
	21st to end	Day	15% 4 19% 31% 22% 10%	894
August	1st to 10th	Day	15% 7% 16% 23% 25% 14%	529
	11th to 20th	Day	10% 9% 27% 31% 18% 4	477
	21st to end	Day	17% 7% 27% 27% 16% 7%	539
September	1st to 10th	Day	18% 5% 25% 29% 18% 6%	490
	11th to 20th	Day	14% 8% 22% 32% 18% 6%	490
	21st to end	Day	13% 12% 30% 26% 15% 3	490
October	1st to 10th	Day	17% 10% 24% 30% 15% 4	464
	11th to 20th	Day	19% 6% 27% 29% 16% 3	300
	21st to end	Day	18% 6% 29% 30% 14% 3	327
November	1st to 10th	Day	15% 6% 34% 28% 15% 4	200
	11th to 20th	Day	16% 5% 33% 28% 16% 3	200
	21st to end	Day	11% 8% 33% 31% 18% 1	200
December	1st to 10th	Day	8% 8% 30% 36% 15% 5%	200
	11th to 20th	Day	12% 8% 24% 39% 16% 2	200
	21st to end	Day	8% 5% 21% 40% 22% 5%	220
January	1st to 10th	Night	13% 4 26% 38% 16% 3	1077
	11th to 20th	Night	14% 5% 27% 36% 16% 1	1040
	21st to end	Night	18% 8% 27% 34% 12% 1	986
February	1st to 10th	Night	12% 4 26% 35% 20% 3	760
	11th to 20th	Night	12% 4 23% 42% 17% 2	744
	21st to end	Night	5% 4 28% 40% 20% 4	628
March	1st to 10th	Night	9% 5% 27% 34% 22% 3	760
	11th to 20th	Night	12% 5% 23% 41% 18% 1	760
	21st to end	Night	13% 5% 19% 37% 24% 2	836
April	1st to 10th	Night	10% 6% 22% 40% 20% 2	743
	11th to 20th	Night	13% 5% 23% 34% 23% 3	550
	21st to end	Night	17% 2 24% 38% 16% 2	380
May	1st to 10th	Night	13% 6% 17% 39% 24% 2	380
	11th to 20th	Night	9% 6% 24% 36% 23% 2	374
	21st to end	Night	17% 2 13% 38% 27% 2	411
June	1st to 10th	Night	13% 5% 14% 41% 27%	380
	11th to 20th	Night	19% 4 13% 35% 24% 4	380
	21st to end	Night	12% 3 15% 38% 28% 4	380
July	1st to 10th	Night	14% 3 13% 37% 30% 3	370
	11th to 20th	Night	13% 3 10% 38% 34% 2	368
	21st to end	Night	14% 2 14% 35% 33% 3	416
August	1st to 10th	Night	10% 3 8% 35% 38% 6%	378
	11th to 20th	Night	9% 2 19% 46% 22% 2	376
	21st to end	Night	17% 2 16% 40% 22% 3	550
September	1st to 10th	Night	17% 2 17% 36% 25% 3	721
	11th to 20th	Night	11% 3 17% 41% 24% 3	760
	21st to end	Night	13% 8% 28% 33% 15% 3	760
October	1st to 10th	Night	17% 7% 24% 35% 16% 2	760
	11th to 20th	Night	14% 5% 26% 36% 16% 2	760
	21st to end	Night	19% 9% 21% 37% 13% 1	836
November	1st to 10th	Night	18% 7% 25% 35% 15% 2	930
	11th to 20th	Night	16% 8% 27% 38% 10% 1	1000
	21st to end	Night	13% 7% 31% 37% 11% 1	1013
December	1st to 10th	Night	15% 6% 30% 35% 12% 2	1100
	11th to 20th	Night	15% 6% 27% 38% 13% 2	1100
	21st to end	Night	11% 4 25% 36% 21% 3	1210

Page generated at 2025-01-04 01:23:57. Version ac07

Copyright © 2025 Attilla Danko.