Pickering
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pickering clear sky chart from 2005-11-06 to 2026-07-01.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	138198
	Night	15% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	134125
Transparency	Day	46% 6% 14% 22% 12% 1	141789
	Night	49% 6% 12% 20% 12% 1	138620
Seeing	Day	17% 6% 21% 31% 19% 5%	16490
	Night	19% 7% 26% 31% 15% 3	25877

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	16% 11% 4 10% 5% 5% 5% 3 5% 5% 31%	4661
	11th to 20th	Day	10% 18% 7% 16% 8% 6% 5% 4 4 5% 16%	5007
	21st to end	Day	14% 14% 6% 13% 6% 6% 5% 4 5% 6% 22%	5780
February	1st to 10th	Day	15% 14% 4 12% 6% 6% 5% 4 4 6% 24%	1890
	11th to 20th	Day	14% 12% 5% 13% 7% 5% 4 3 4 6% 27%	1843
	21st to end	Day	17% 13% 4 10% 6% 5% 4 3 5% 5% 27%	1610
March	1st to 10th	Day	19% 9% 3 8% 5% 5% 4 3 5% 6% 32%	5042
	11th to 20th	Day	12% 11% 4 9% 6% 5% 6% 4 6% 8% 31%	5090
	21st to end	Day	18% 10% 4 7% 4 4 4 3 5% 6% 35%	5586
April	1st to 10th	Day	18% 11% 4 9% 5% 4 5% 3 6% 7% 30%	2499
	11th to 20th	Day	19% 10% 2 7% 4 4 5% 4 5% 6% 35%	2550
	21st to end	Day	19% 8% 3 7% 5% 5% 5% 4 6% 5% 34%	2730
May	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 4 5% 7% 31%	7678
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 4 6% 9% 35%	8221
	21st to end	Day	17% 5% 2 5% 4 4 4 3 5% 8% 43%	9060
June	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 4 7% 8% 38%	2940
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 39%	2940
	21st to end	Day	13% 6% 2 5% 5% 4 4 4 7% 9% 41%	2940
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 5% 4 7% 10% 42%	6360
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 6% 9% 48%	6360
	21st to end	Day	6% 4 2 5% 5% 5% 5% 5% 7% 9% 47%	6565
August	1st to 10th	Day	15% 7% 3 6% 4 4 4 4 6% 7% 40%	4234
	11th to 20th	Day	10% 6% 3 7% 5% 4 5% 4 7% 10% 39%	4174
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 45%	4460
September	1st to 10th	Day	12% 5% 2 5% 4 4 6% 4 6% 7% 45%	2400
	11th to 20th	Day	10% 5% 2 4 5% 4 5% 3 6% 8% 50%	2310
	21st to end	Day	13% 5% 3 7% 5% 5% 4 4 6% 9% 39%	2141
October	1st to 10th	Day	16% 7% 2 7% 4 4 5% 4 5% 7% 39%	2000
	11th to 20th	Day	18% 9% 3 7% 5% 4 5% 4 6% 7% 33%	2000
	21st to end	Day	22% 10% 4 8% 5% 5% 5% 3 5% 7% 26%	2200
November	1st to 10th	Day	14% 9% 2 9% 5% 5% 5% 4 6% 8% 34%	1773
	11th to 20th	Day	14% 11% 4 10% 5% 6% 6% 4 7% 7% 26%	1680
	21st to end	Day	18% 12% 4 9% 6% 5% 6% 4 5% 8% 23%	1680
December	1st to 10th	Day	18% 14% 5% 12% 6% 7% 7% 4 7% 6% 15%	2680
	11th to 20th	Day	20% 14% 4 9% 5% 4 4 4 5% 6% 25%	3066
	21st to end	Day	27% 15% 6% 12% 6% 4 4 3 4 5% 15%	4048
January	1st to 10th	Night	15% 12% 4 10% 5% 5% 5% 4 6% 6% 29%	8234
	11th to 20th	Night	13% 15% 6% 13% 8% 6% 6% 4 5% 6% 19%	7862
	21st to end	Night	13% 12% 4 10% 6% 6% 6% 5% 6% 7% 25%	8401
February	1st to 10th	Night	13% 15% 4 9% 6% 5% 5% 4 5% 6% 27%	2730
	11th to 20th	Night	15% 12% 5% 10% 6% 5% 5% 4 5% 6% 27%	2663
	21st to end	Night	14% 13% 4 10% 5% 5% 5% 5% 5% 6% 30%	2192
March	1st to 10th	Night	16% 10% 4 8% 5% 4 5% 3 5% 6% 33%	5018
	11th to 20th	Night	11% 8% 3 7% 6% 5% 5% 4 7% 8% 37%	5089
	21st to end	Night	20% 7% 3 6% 4 4 4 3 5% 5% 39%	5588
April	1st to 10th	Night	18% 10% 3 8% 5% 4 4 4 6% 6% 33%	2121
	11th to 20th	Night	16% 7% 3 7% 5% 5% 5% 3 5% 6% 39%	2037
	21st to end	Night	15% 8% 2 6% 5% 5% 5% 4 6% 7% 36%	1890
May	1st to 10th	Night	22% 7% 3 6% 4 4 4 4 5% 6% 35%	5206
	11th to 20th	Night	15% 7% 2 8% 5% 5% 6% 4 6% 8% 35%	4639
	21st to end	Night	17% 5% 2 6% 3 4 4 3 5% 7% 45%	5114
June	1st to 10th	Night	12% 5% 2 6% 4 5% 5% 4 6% 7% 44%	1680
	11th to 20th	Night	8% 5% 2 7% 6% 4 4 4 6% 9% 44%	1680
	21st to end	Night	12% 6% 2 5% 5% 5% 5% 4 6% 9% 42%	1680
July	1st to 10th	Night	7% 5% 2 7% 4 4 4 4 6% 9% 46%	3600
	11th to 20th	Night	9% 4 2 6% 4 4 4 3 5% 9% 50%	3600
	21st to end	Night	9% 5% 2 4 3 4 4 4 6% 8% 53%	4283
August	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 6% 8% 48%	2915
	11th to 20th	Night	12% 5% 1 6% 3 3 3 3 5% 7% 51%	2875
	21st to end	Night	9% 5% 2 6% 4 4 4 4 6% 8% 47%	3403
September	1st to 10th	Night	9% 5% 2 6% 4 4 4 5% 5% 7% 48%	2000
	11th to 20th	Night	10% 4 2 4 3 4 3 3 5% 7% 56%	2087
	21st to end	Night	16% 6% 2 7% 4 4 4 3 5% 7% 42%	2257
October	1st to 10th	Night	15% 6% 3 6% 4 4 4 3 5% 7% 42%	2400
	11th to 20th	Night	19% 8% 3 7% 5% 5% 4 3 6% 6% 34%	2400
	21st to end	Night	21% 8% 4 7% 4 4 5% 4 5% 6% 32%	2640
November	1st to 10th	Night	16% 7% 2 7% 5% 4 4 4 5% 7% 38%	2743
	11th to 20th	Night	16% 10% 3 7% 6% 5% 5% 4 6% 7% 31%	2940
	21st to end	Night	19% 11% 3 8% 5% 5% 5% 5% 6% 8% 25%	2940
December	1st to 10th	Night	17% 13% 4 10% 6% 6% 5% 4 5% 7% 21%	4720
	11th to 20th	Night	17% 15% 4 9% 5% 5% 5% 4 5% 6% 25%	5348
	21st to end	Night	26% 13% 7% 11% 6% 5% 4 4 5% 5% 15%	7150

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	53% 6% 15% 15% 10%	4662
	11th to 20th	Day	70% 7% 8% 10% 5%	5040
	21st to end	Day	62% 6% 11% 11% 9%	5780
February	1st to 10th	Day	62% 6% 11% 16% 5% 1	1890
	11th to 20th	Day	58% 7% 12% 16% 7% 1	1852
	21st to end	Day	57% 5% 13% 18% 6%	1610
March	1st to 10th	Day	52% 6% 13% 16% 13% 1	5045
	11th to 20th	Day	50% 5% 18% 18% 8% 2	5090
	21st to end	Day	48% 4 11% 22% 14% 1	5586
April	1st to 10th	Day	51% 6% 12% 19% 11% 1	2499
	11th to 20th	Day	49% 6% 9% 22% 13% 1	2550
	21st to end	Day	49% 6% 11% 19% 12% 3	2730
May	1st to 10th	Day	50% 5% 14% 18% 11% 3	7687
	11th to 20th	Day	46% 8% 11% 19% 14% 1	8225
	21st to end	Day	40% 4 12% 28% 14% 2	9061
June	1st to 10th	Day	40% 7% 13% 22% 16% 1	2940
	11th to 20th	Day	37% 7% 14% 25% 15% 2	2940
	21st to end	Day	37% 6% 17% 25% 14% 1	2940
July	1st to 10th	Day	35% 5% 16% 27% 16% 2	6290
	11th to 20th	Day	31% 5% 14% 33% 16% 1	6285
	21st to end	Day	32% 5% 15% 31% 16% 1	6377
August	1st to 10th	Day	41% 5% 15% 23% 15% 1	4221
	11th to 20th	Day	37% 5% 18% 28% 11% 1	4213
	21st to end	Day	33% 5% 15% 36% 10% 1	4460
September	1st to 10th	Day	35% 8% 14% 30% 12% 1	2400
	11th to 20th	Day	31% 7% 16% 31% 14% 1	2310
	21st to end	Day	41% 6% 16% 27% 10% 1	2141
October	1st to 10th	Day	35% 5% 16% 28% 15% 1	3260
	11th to 20th	Day	38% 5% 18% 25% 15%	3240
	21st to end	Day	49% 4 17% 22% 6%	3538
November	1st to 10th	Day	47% 6% 15% 21% 9% 1	1773
	11th to 20th	Day	54% 8% 14% 15% 8% 1	1680
	21st to end	Day	59% 7% 15% 16% 3	1680
December	1st to 10th	Day	67% 4 17% 9% 3	2680
	11th to 20th	Day	61% 7% 13% 10% 9%	3066
	21st to end	Day	72% 8% 7% 9% 4	4048
January	1st to 10th	Night	54% 6% 15% 19% 5%	8234
	11th to 20th	Night	66% 10% 7% 10% 6%	7903
	21st to end	Night	58% 9% 10% 12% 11% 1	8401
February	1st to 10th	Night	58% 7% 11% 18% 5% 1	2730
	11th to 20th	Night	58% 6% 11% 17% 8% 1	2665
	21st to end	Night	55% 5% 13% 19% 8%	2192
March	1st to 10th	Night	52% 4 10% 18% 13% 2	5028
	11th to 20th	Night	44% 4 18% 22% 10% 1	5090
	21st to end	Night	47% 4 9% 21% 17% 2	5588
April	1st to 10th	Night	51% 4 11% 19% 14% 1	2121
	11th to 20th	Night	47% 5% 10% 21% 16% 2	2037
	21st to end	Night	45% 6% 11% 20% 15% 2	1890
May	1st to 10th	Night	50% 5% 11% 16% 14% 4	5213
	11th to 20th	Night	47% 8% 11% 19% 14% 2	4640
	21st to end	Night	41% 4 11% 26% 16% 2	5115
June	1st to 10th	Night	38% 5% 12% 25% 17% 3	1680
	11th to 20th	Night	37% 5% 12% 24% 20% 2	1680
	21st to end	Night	39% 6% 13% 24% 17% 1	1680
July	1st to 10th	Night	35% 4 15% 24% 20% 2	3560
	11th to 20th	Night	33% 5% 13% 32% 17% 1	3552
	21st to end	Night	30% 5% 12% 28% 23% 1	4156
August	1st to 10th	Night	35% 5% 15% 28% 15% 2	2904
	11th to 20th	Night	34% 5% 15% 32% 13% 1	2902
	21st to end	Night	35% 6% 12% 32% 14% 1	3403
September	1st to 10th	Night	34% 7% 14% 30% 14% 1	2000
	11th to 20th	Night	28% 6% 12% 35% 18%	2087
	21st to end	Night	42% 6% 12% 27% 12% 1	2257
October	1st to 10th	Night	34% 5% 9% 27% 24% 1	3920
	11th to 20th	Night	43% 5% 14% 28% 9%	3899
	21st to end	Night	41% 5% 15% 28% 11% 1	4252
November	1st to 10th	Night	45% 6% 13% 23% 13% 1	2743
	11th to 20th	Night	51% 7% 15% 17% 9% 1	2940
	21st to end	Night	57% 8% 17% 15% 4	2940
December	1st to 10th	Night	62% 5% 15% 15% 4	4720
	11th to 20th	Night	60% 6% 11% 13% 9% 1	5348
	21st to end	Night	71% 6% 11% 8% 4	7150

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	22% 13% 30% 25% 9%	220
	11th to 20th	Day	22% 16% 35% 17% 9% 1	286
	21st to end	Day	23% 11% 33% 26% 6% 1	363
February	1st to 10th	Day	20% 12% 36% 22% 9% 1	330
	11th to 20th	Day	19% 14% 36% 25% 6%	330
	21st to end	Day	21% 17% 28% 28% 5%	310
March	1st to 10th	Day	21% 7% 35% 29% 8%	540
	11th to 20th	Day	19% 12% 30% 29% 9% 1	540
	21st to end	Day	25% 6% 30% 30% 8% 1	594
April	1st to 10th	Day	18% 9% 29% 35% 8% 1	540
	11th to 20th	Day	26% 5% 27% 27% 12% 3	532
	21st to end	Day	21% 5% 25% 33% 14% 1	540
May	1st to 10th	Day	20% 4 18% 36% 17% 5%	543
	11th to 20th	Day	14% 2 16% 39% 24% 5%	567
	21st to end	Day	14% 2 14% 38% 27% 6%	617
June	1st to 10th	Day	13% 4 15% 40% 23% 4	570
	11th to 20th	Day	12% 3 14% 37% 30% 4	570
	21st to end	Day	15% 3 11% 39% 28% 4	570
July	1st to 10th	Day	8% 1 10% 35% 38% 8%	525
	11th to 20th	Day	13% 2 9% 32% 35% 9%	524
	21st to end	Day	8% 3 10% 39% 33% 7%	576
August	1st to 10th	Day	11% 2 9% 32% 34% 12%	526
	11th to 20th	Day	10% 2 10% 33% 32% 13%	519
	21st to end	Day	11% 2 13% 30% 33% 10%	583
September	1st to 10th	Day	11% 3 15% 31% 28% 12%	530
	11th to 20th	Day	8% 2 11% 29% 28% 22%	530
	21st to end	Day	15% 4 18% 31% 22% 9%	530
October	1st to 10th	Day	19% 5% 21% 26% 21% 8%	530
	11th to 20th	Day	19% 7% 31% 29% 11% 3	530
	21st to end	Day	26% 8% 26% 26% 13% 1	583
November	1st to 10th	Day	22% 9% 24% 28% 15% 2	320
	11th to 20th	Day	20% 11% 28% 30% 11%	220
	21st to end	Day	25% 9% 36% 24% 7%	220
December	1st to 10th	Day	23% 9% 33% 25% 8% 2	220
	11th to 20th	Day	24% 15% 35% 20% 6%	220
	21st to end	Day	29% 11% 37% 18% 5% 1	242
January	1st to 10th	Night	23% 11% 38% 19% 7%	840
	11th to 20th	Night	27% 12% 32% 23% 5%	840
	21st to end	Night	19% 11% 37% 27% 7% 1	924
February	1st to 10th	Night	20% 13% 38% 24% 5%	840
	11th to 20th	Night	21% 12% 35% 26% 6%	823
	21st to end	Night	20% 10% 41% 24% 5%	692
March	1st to 10th	Night	19% 7% 34% 33% 6%	840
	11th to 20th	Night	20% 8% 36% 27% 7% 1	840
	21st to end	Night	20% 6% 29% 32% 12% 1	924
April	1st to 10th	Night	23% 6% 28% 35% 8% 1	840
	11th to 20th	Night	18% 6% 27% 35% 12% 2	793
	21st to end	Night	20% 5% 22% 39% 13% 1	630
May	1st to 10th	Night	19% 3 17% 39% 20% 2	617
	11th to 20th	Night	17% 1 18% 41% 22% 2	414
	21st to end	Night	11% 3 13% 41% 28% 4	455
June	1st to 10th	Night	13% 2 14% 42% 26% 3	420
	11th to 20th	Night	10% 3 15% 40% 28% 2	420
	21st to end	Night	12% 2 13% 41% 29% 3	420
July	1st to 10th	Night	7% 3 8% 44% 33% 6%	390
	11th to 20th	Night	12% 3 10% 36% 34% 5%	388
	21st to end	Night	9% 3 8% 42% 33% 4	590
August	1st to 10th	Night	10% 2 10% 34% 38% 7%	597
	11th to 20th	Night	9% 2 10% 36% 35% 8%	594
	21st to end	Night	11% 3 15% 35% 31% 5%	762
September	1st to 10th	Night	11% 3 17% 34% 27% 8%	800
	11th to 20th	Night	12% 4 13% 28% 32% 12%	800
	21st to end	Night	18% 5% 16% 30% 26% 6%	800
October	1st to 10th	Night	18% 4 24% 28% 21% 6%	800
	11th to 20th	Night	23% 7% 26% 31% 11% 2	800
	21st to end	Night	25% 7% 26% 33% 9% 1	880
November	1st to 10th	Night	21% 6% 26% 34% 11% 2	820
	11th to 20th	Night	21% 9% 33% 27% 8% 2	840
	21st to end	Night	25% 9% 32% 28% 7%	840
December	1st to 10th	Night	28% 10% 33% 23% 5%	840
	11th to 20th	Night	21% 11% 41% 22% 4 1	840
	21st to end	Night	30% 10% 34% 22% 4	924

Page generated at 2026-06-28 02:10:42. Version ac07

Copyright © 2026 Attilla Danko.