Walkerton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walkerton clear sky chart from 2005-11-06 to 2024-11-08.

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	15% 12% 4 9% 5% 5% 4 4 5% 6% 30%	101583
	Night	15% 13% 5% 11% 6% 5% 4 3 5% 6% 28%	97548
Transparency	Day	52% 7% 12% 18% 10% 1	105143
	Night	56% 7% 11% 17% 9% 1	102064
Seeing	Day	19% 13% 29% 23% 12% 4	15140
	Night	21% 11% 29% 28% 10% 1	24343

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	14% 21% 10% 18% 8% 6% 4 2 3 4 10%	2276
	11th to 20th	Day	10% 21% 10% 23% 15% 6% 3 2 2 2 5%	2685
	21st to end	Day	18% 22% 9% 16% 8% 6% 4 3 3 3 8%	3124
February	1st to 10th	Day	13% 20% 6% 18% 9% 7% 4 3 4 4 13%	1710
	11th to 20th	Day	12% 16% 9% 19% 9% 4 5% 3 5% 4 13%	1663
	21st to end	Day	15% 19% 7% 13% 7% 5% 4 4 4 4 18%	1540
March	1st to 10th	Day	16% 16% 5% 11% 6% 4 3 3 3 5% 27%	3336
	11th to 20th	Day	11% 17% 9% 13% 5% 4 4 4 4 5% 25%	3480
	21st to end	Day	15% 13% 5% 12% 5% 4 4 4 5% 5% 27%	3815
April	1st to 10th	Day	16% 16% 5% 9% 5% 4 4 3 5% 6% 27%	2175
	11th to 20th	Day	18% 13% 2 6% 4 3 3 3 4 6% 35%	2441
	21st to end	Day	20% 12% 3 7% 4 4 4 3 5% 7% 32%	2470
May	1st to 10th	Day	17% 9% 3 7% 4 4 4 4 6% 7% 35%	4108
	11th to 20th	Day	17% 9% 3 7% 4 4 4 4 5% 8% 35%	4205
	21st to end	Day	14% 6% 2 5% 4 4 3 3 5% 7% 46%	4837
June	1st to 10th	Day	15% 8% 2 7% 4 5% 4 4 6% 6% 39%	2748
	11th to 20th	Day	12% 6% 2 5% 5% 5% 5% 4 6% 8% 43%	2850
	21st to end	Day	16% 7% 2 6% 4 4 4 3 6% 8% 40%	2850
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 6% 5% 7% 8% 37%	4760
	11th to 20th	Day	12% 5% 2 5% 3 4 5% 4 6% 8% 44%	4523
	21st to end	Day	9% 6% 3 6% 4 5% 5% 4 7% 9% 44%	4466
August	1st to 10th	Day	12% 6% 2 7% 5% 6% 6% 5% 7% 8% 36%	4104
	11th to 20th	Day	13% 8% 2 7% 6% 5% 5% 4 7% 9% 34%	4044
	21st to end	Day	9% 5% 3 6% 4 4 5% 5% 7% 8% 43%	4483
September	1st to 10th	Day	13% 8% 2 7% 4 4 5% 4 6% 8% 39%	2249
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 6% 7% 44%	2090
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 5% 6% 7% 34%	2090
October	1st to 10th	Day	19% 9% 3 8% 4 5% 4 3 5% 7% 33%	1929
	11th to 20th	Day	22% 15% 3 10% 5% 4 5% 3 5% 7% 21%	1900
	21st to end	Day	26% 15% 4 9% 6% 5% 6% 3 5% 4 17%	2028
November	1st to 10th	Day	15% 20% 4 10% 5% 5% 3 3 4 5% 25%	1716
	11th to 20th	Day	16% 18% 5% 12% 5% 5% 6% 4 4 6% 17%	1520
	21st to end	Day	18% 23% 8% 10% 6% 6% 4 4 4 5% 13%	1520
December	1st to 10th	Day	14% 28% 9% 17% 9% 4 4 2 3 4 6%	1520
	11th to 20th	Day	18% 21% 8% 17% 6% 5% 4 3 4 5% 10%	1897
	21st to end	Day	25% 24% 8% 13% 6% 4 3 2 3 3 8%	2431
January	1st to 10th	Night	15% 22% 10% 20% 7% 5% 4 3 3 4 7%	4676
	11th to 20th	Night	12% 16% 8% 21% 13% 9% 5% 3 4 3 6%	4277
	21st to end	Night	18% 18% 10% 18% 8% 6% 5% 3 3 3 8%	4532
February	1st to 10th	Night	13% 22% 6% 15% 10% 6% 5% 3 3 4 13%	2470
	11th to 20th	Night	12% 16% 8% 17% 8% 5% 5% 3 4 5% 17%	2403
	21st to end	Night	14% 15% 6% 12% 8% 5% 5% 4 5% 5% 21%	1913
March	1st to 10th	Night	12% 15% 5% 9% 5% 4 4 3 5% 6% 32%	3503
	11th to 20th	Night	9% 16% 5% 11% 5% 4 5% 4 4 5% 31%	3479
	21st to end	Night	14% 11% 5% 12% 5% 5% 4 3 4 5% 31%	3817
April	1st to 10th	Night	19% 15% 4 8% 4 4 3 4 4 6% 29%	2005
	11th to 20th	Night	18% 10% 2 7% 4 5% 4 4 5% 6% 36%	1704
	21st to end	Night	17% 11% 4 8% 5% 5% 4 4 5% 6% 31%	1710
May	1st to 10th	Night	15% 8% 3 6% 5% 4 4 3 5% 7% 40%	2833
	11th to 20th	Night	15% 8% 3 8% 4 4 5% 4 4 7% 39%	2686
	21st to end	Night	10% 6% 2 6% 4 4 4 3 5% 7% 49%	2738
June	1st to 10th	Night	14% 7% 2 7% 5% 5% 3 4 5% 8% 40%	1426
	11th to 20th	Night	11% 7% 1 7% 5% 4 5% 5% 6% 9% 41%	1330
	21st to end	Night	13% 6% 2 7% 4 4 5% 5% 4 8% 43%	1330
July	1st to 10th	Night	7% 6% 3 8% 4 3 3 3 6% 8% 48%	2210
	11th to 20th	Night	12% 5% 2 4 4 3 4 3 5% 6% 52%	2437
	21st to end	Night	7% 6% 2 6% 5% 5% 4 4 6% 9% 47%	3087
August	1st to 10th	Night	11% 7% 2 7% 4 5% 3 3 5% 6% 46%	2825
	11th to 20th	Night	14% 8% 3 7% 4 4 4 4 5% 9% 39%	2785
	21st to end	Night	12% 7% 2 5% 4 4 4 3 5% 6% 47%	3139
September	1st to 10th	Night	9% 6% 2 7% 4 5% 4 3 6% 8% 46%	1928
	11th to 20th	Night	12% 5% 2 4 4 4 4 3 5% 7% 50%	2090
	21st to end	Night	14% 7% 3 7% 5% 5% 4 3 5% 7% 38%	2090
October	1st to 10th	Night	17% 9% 3 7% 5% 4 4 3 6% 6% 37%	2250
	11th to 20th	Night	23% 11% 3 8% 5% 4 5% 4 5% 7% 25%	2280
	21st to end	Night	23% 15% 4 8% 6% 4 5% 3 5% 5% 22%	2565
November	1st to 10th	Night	17% 15% 3 8% 6% 5% 5% 4 5% 6% 27%	2522
	11th to 20th	Night	17% 18% 6% 10% 5% 5% 5% 4 6% 6% 18%	2660
	21st to end	Night	20% 20% 7% 11% 6% 4 4 3 4 6% 15%	2660
December	1st to 10th	Night	19% 26% 8% 13% 6% 5% 4 3 4 4 8%	2660
	11th to 20th	Night	14% 21% 9% 15% 7% 5% 4 4 5% 5% 12%	3292
	21st to end	Night	23% 22% 9% 15% 6% 5% 4 3 3 3 7%	5236

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	78% 7% 9% 5% 1	2277
	11th to 20th	Day	87% 5% 3 3 2	2685
	21st to end	Day	81% 6% 7% 4 2	3124
February	1st to 10th	Day	76% 6% 7% 9% 1	1710
	11th to 20th	Day	73% 7% 7% 8% 4	1672
	21st to end	Day	68% 7% 8% 11% 5%	1540
March	1st to 10th	Day	60% 5% 12% 15% 7%	3339
	11th to 20th	Day	59% 7% 12% 16% 5% 1	3480
	21st to end	Day	55% 8% 13% 14% 9% 1	3815
April	1st to 10th	Day	58% 6% 10% 17% 9%	2175
	11th to 20th	Day	49% 7% 10% 21% 14% 1	2441
	21st to end	Day	51% 6% 11% 17% 11% 2	2470
May	1st to 10th	Day	44% 9% 12% 19% 15% 1	4120
	11th to 20th	Day	44% 8% 14% 24% 8% 1	4209
	21st to end	Day	36% 8% 11% 21% 19% 5%	4837
June	1st to 10th	Day	43% 7% 12% 22% 14% 1	2748
	11th to 20th	Day	38% 7% 12% 24% 18% 1	2850
	21st to end	Day	42% 6% 13% 24% 14% 1	2850
July	1st to 10th	Day	41% 7% 15% 19% 16% 2	4686
	11th to 20th	Day	34% 7% 13% 32% 13% 1	4442
	21st to end	Day	35% 7% 12% 25% 18% 2	4324
August	1st to 10th	Day	41% 8% 14% 22% 14% 1	4091
	11th to 20th	Day	45% 7% 16% 22% 10%	4083
	21st to end	Day	36% 7% 15% 30% 12% 1	4483
September	1st to 10th	Day	42% 7% 14% 23% 11% 2	2249
	11th to 20th	Day	37% 7% 14% 27% 14%	2090
	21st to end	Day	46% 8% 14% 23% 8% 1	2090
October	1st to 10th	Day	46% 6% 12% 23% 12% 1	3202
	11th to 20th	Day	49% 6% 13% 22% 9%	3140
	21st to end	Day	61% 6% 13% 16% 4	3317
November	1st to 10th	Day	61% 7% 10% 15% 6%	1716
	11th to 20th	Day	66% 9% 11% 8% 5% 1	1520
	21st to end	Day	75% 7% 9% 8% 1	1520
December	1st to 10th	Day	84% 6% 6% 4 1	1520
	11th to 20th	Day	77% 8% 8% 6% 1	1897
	21st to end	Day	82% 6% 8% 3	2431
January	1st to 10th	Night	81% 7% 7% 4 1	4676
	11th to 20th	Night	83% 8% 5% 2 2	4277
	21st to end	Night	80% 7% 7% 4 2	4532
February	1st to 10th	Night	76% 5% 8% 9% 1	2470
	11th to 20th	Night	70% 6% 10% 11% 3	2405
	21st to end	Night	63% 8% 11% 12% 7%	1913
March	1st to 10th	Night	51% 7% 15% 19% 7%	3513
	11th to 20th	Night	51% 9% 12% 17% 8% 1	3480
	21st to end	Night	52% 8% 11% 18% 9% 1	3817
April	1st to 10th	Night	56% 6% 10% 17% 11% 1	2005
	11th to 20th	Night	48% 7% 8% 19% 16% 1	1704
	21st to end	Night	52% 7% 9% 16% 14% 2	1710
May	1st to 10th	Night	42% 7% 12% 20% 15% 4	2840
	11th to 20th	Night	42% 9% 12% 21% 14% 2	2687
	21st to end	Night	34% 8% 12% 23% 21% 3	2739
June	1st to 10th	Night	42% 7% 10% 22% 17% 2	1426
	11th to 20th	Night	38% 8% 13% 24% 16% 2	1330
	21st to end	Night	39% 6% 12% 25% 17% 1	1330
July	1st to 10th	Night	34% 5% 13% 24% 18% 6%	2175
	11th to 20th	Night	31% 6% 11% 34% 16% 1	2395
	21st to end	Night	33% 7% 15% 25% 18% 1	2988
August	1st to 10th	Night	39% 6% 11% 28% 16% 1	2814
	11th to 20th	Night	42% 8% 15% 22% 12% 1	2812
	21st to end	Night	37% 6% 11% 31% 14% 1	3139
September	1st to 10th	Night	36% 7% 13% 29% 13% 2	1928
	11th to 20th	Night	33% 7% 14% 29% 17%	2090
	21st to end	Night	45% 8% 13% 23% 11%	2090
October	1st to 10th	Night	38% 6% 9% 27% 19% 1	3757
	11th to 20th	Night	48% 6% 16% 18% 12%	3779
	21st to end	Night	54% 6% 16% 19% 6%	4213
November	1st to 10th	Night	57% 7% 12% 18% 6%	2522
	11th to 20th	Night	64% 9% 11% 11% 4 1	2660
	21st to end	Night	72% 7% 11% 8% 2	2660
December	1st to 10th	Night	80% 8% 6% 4 1	2660
	11th to 20th	Night	74% 9% 11% 5% 1	3292
	21st to end	Night	82% 7% 7% 4	5236

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	20% 20% 36% 18% 6% 1	200
	11th to 20th	Day	22% 20% 39% 14% 6% 1	270
	21st to end	Day	25% 15% 32% 23% 3 1	297
February	1st to 10th	Day	22% 24% 37% 11% 6%	270
	11th to 20th	Day	24% 21% 41% 12% 1	270
	21st to end	Day	27% 30% 28% 13% 1	225
March	1st to 10th	Day	23% 17% 36% 16% 7% 1	398
	11th to 20th	Day	21% 16% 34% 21% 7% 1	460
	21st to end	Day	27% 14% 31% 20% 7% 1	506
April	1st to 10th	Day	22% 17% 32% 21% 7% 1	460
	11th to 20th	Day	29% 15% 26% 16% 8% 6%	452
	21st to end	Day	24% 14% 27% 26% 7% 3	460
May	1st to 10th	Day	22% 13% 28% 25% 10% 2	463
	11th to 20th	Day	19% 10% 26% 25% 15% 4	487
	21st to end	Day	15% 9% 26% 27% 15% 7%	529
June	1st to 10th	Day	15% 10% 28% 28% 16% 3	578
	11th to 20th	Day	13% 10% 30% 30% 14% 3	680
	21st to end	Day	18% 8% 33% 27% 12% 2	680
July	1st to 10th	Day	10% 7% 27% 30% 21% 6%	671
	11th to 20th	Day	12% 7% 31% 29% 15% 7%	621
	21st to end	Day	10% 5% 27% 33% 17% 8%	532
August	1st to 10th	Day	11% 5% 25% 30% 17% 11%	486
	11th to 20th	Day	14% 6% 18% 28% 21% 13%	479
	21st to end	Day	14% 7% 21% 30% 20% 9%	539
September	1st to 10th	Day	14% 9% 23% 27% 18% 9%	490
	11th to 20th	Day	10% 6% 20% 26% 23% 15%	490
	21st to end	Day	16% 10% 28% 25% 13% 7%	490
October	1st to 10th	Day	22% 12% 26% 21% 14% 6%	490
	11th to 20th	Day	24% 19% 29% 21% 5% 1	490
	21st to end	Day	33% 20% 26% 17% 4	477
November	1st to 10th	Day	25% 18% 31% 17% 8%	282
	11th to 20th	Day	28% 17% 32% 16% 3 3	180
	21st to end	Day	29% 24% 32% 14% 2	180
December	1st to 10th	Day	27% 29% 29% 12% 3	180
	11th to 20th	Day	29% 22% 32% 12% 3 1	180
	21st to end	Day	37% 17% 33% 11% 2 1	198
January	1st to 10th	Night	23% 18% 33% 19% 6% 1	950
	11th to 20th	Night	26% 17% 33% 19% 5% 1	852
	21st to end	Night	19% 12% 36% 27% 6% 1	836
February	1st to 10th	Night	22% 17% 36% 22% 3	760
	11th to 20th	Night	21% 15% 35% 23% 4	743
	21st to end	Night	22% 17% 36% 21% 3	628
March	1st to 10th	Night	19% 15% 36% 24% 7% 1	760
	11th to 20th	Night	18% 17% 35% 25% 5% 1	760
	21st to end	Night	23% 11% 31% 27% 8% 1	836
April	1st to 10th	Night	25% 14% 30% 26% 4	760
	11th to 20th	Night	21% 14% 28% 27% 9% 1	580
	21st to end	Night	22% 11% 26% 31% 9%	570
May	1st to 10th	Night	19% 5% 29% 35% 11% 1	570
	11th to 20th	Night	19% 6% 23% 39% 12% 1	487
	21st to end	Night	12% 4 26% 42% 16%	411
June	1st to 10th	Night	15% 7% 24% 42% 11% 1	380
	11th to 20th	Night	12% 8% 27% 41% 13%	380
	21st to end	Night	17% 4 23% 41% 14% 1	380
July	1st to 10th	Night	7% 4 20% 50% 19% 1	370
	11th to 20th	Night	11% 4 22% 38% 24% 1	450
	21st to end	Night	11% 4 18% 44% 22% 1	624
August	1st to 10th	Night	12% 3 16% 39% 29% 1	567
	11th to 20th	Night	12% 3 15% 37% 29% 4	564
	21st to end	Night	14% 3 21% 33% 26% 2	629
September	1st to 10th	Night	12% 5% 24% 35% 19% 5%	760
	11th to 20th	Night	14% 4 19% 36% 23% 4	760
	21st to end	Night	16% 9% 22% 32% 18% 4	760
October	1st to 10th	Night	20% 9% 27% 29% 14% 1	760
	11th to 20th	Night	26% 13% 25% 27% 8% 1	760
	21st to end	Night	31% 13% 31% 22% 3	836
November	1st to 10th	Night	27% 12% 29% 24% 8% 1	771
	11th to 20th	Night	26% 19% 30% 19% 7%	760
	21st to end	Night	29% 15% 31% 22% 3	760
December	1st to 10th	Night	32% 16% 31% 18% 4	760
	11th to 20th	Night	24% 18% 38% 16% 3	764
	21st to end	Night	32% 14% 35% 17% 2	1045

Page generated at 2024-11-05 08:15:47. Version ac07

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