Haldimand
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Haldimand clear sky chart from 2005-11-06 to 2026-05-02.

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% 10% 4 9% 5% 5% 4 4 5% 7% 32%	131930
	Night	15% 11% 4 8% 5% 4 4 4 5% 7% 33%	130525
Transparency	Day	34% 37% 8% 13% 8% 1	135525
	Night	34% 36% 8% 13% 9% 1	135016
Seeing	Day	19% 12% 28% 24% 13% 4	16308
	Night	20% 10% 29% 28% 12% 1	25920

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	15% 17% 6% 11% 6% 5% 4 3 4 6% 23%	4739
	11th to 20th	Day	10% 22% 9% 20% 8% 6% 4 3 3 4 10%	5246
	21st to end	Day	15% 15% 7% 18% 8% 7% 5% 3 4 5% 14%	5780
February	1st to 10th	Day	16% 18% 5% 13% 7% 6% 3 4 4 5% 19%	1890
	11th to 20th	Day	14% 16% 6% 12% 7% 5% 4 4 5% 4 22%	1843
	21st to end	Day	19% 14% 4 11% 7% 4 4 4 5% 5% 23%	1651
March	1st to 10th	Day	18% 11% 5% 13% 6% 4 3 3 4 5% 29%	5042
	11th to 20th	Day	11% 14% 4 9% 6% 5% 5% 4 5% 7% 32%	5090
	21st to end	Day	19% 12% 4 9% 5% 5% 4 3 4 5% 30%	5586
April	1st to 10th	Day	18% 13% 4 8% 5% 4 4 3 5% 6% 29%	2452
	11th to 20th	Day	17% 10% 3 7% 4 4 4 3 5% 8% 33%	2581
	21st to end	Day	19% 8% 3 8% 5% 4 4 4 5% 6% 34%	2730
May	1st to 10th	Day	20% 9% 3 7% 5% 5% 5% 4 5% 6% 32%	5901
	11th to 20th	Day	16% 10% 3 9% 5% 5% 4 3 5% 8% 31%	6124
	21st to end	Day	16% 7% 3 7% 5% 4 5% 4 5% 7% 38%	6949
June	1st to 10th	Day	12% 6% 3 6% 4 6% 5% 4 7% 7% 40%	2800
	11th to 20th	Day	10% 6% 3 7% 5% 5% 5% 4 7% 8% 39%	2800
	21st to end	Day	12% 5% 2 6% 4 5% 4 5% 7% 9% 42%	2800
July	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 7% 10% 43%	6360
	11th to 20th	Day	9% 6% 2 6% 4 5% 5% 4 7% 10% 42%	6205
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 47%	6424
August	1st to 10th	Day	15% 6% 3 5% 4 4 5% 4 7% 9% 39%	4234
	11th to 20th	Day	10% 7% 3 7% 5% 4 5% 5% 8% 10% 35%	4174
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 6% 9% 43%	4510
September	1st to 10th	Day	12% 7% 2 6% 4 4 5% 4 6% 7% 43%	2400
	11th to 20th	Day	9% 5% 2 5% 4 5% 5% 4 6% 8% 48%	2245
	21st to end	Day	15% 6% 3 7% 5% 4 6% 4 7% 9% 35%	2180
October	1st to 10th	Day	16% 8% 3 7% 5% 5% 4 3 4 7% 39%	2000
	11th to 20th	Day	18% 8% 3 8% 6% 5% 4 4 5% 6% 32%	2000
	21st to end	Day	22% 11% 3 9% 5% 4 4 3 5% 7% 25%	2200
November	1st to 10th	Day	14% 8% 3 8% 6% 4 5% 4 6% 8% 35%	1840
	11th to 20th	Day	14% 13% 4 9% 6% 4 4 4 5% 7% 30%	1680
	21st to end	Day	20% 15% 3 8% 4 5% 4 4 7% 7% 22%	1680
December	1st to 10th	Day	20% 15% 4 10% 6% 6% 6% 5% 6% 7% 14%	2680
	11th to 20th	Day	21% 16% 4 8% 4 4 5% 3 5% 5% 24%	3066
	21st to end	Day	26% 19% 5% 10% 5% 5% 4 3 4 4 15%	4048
January	1st to 10th	Night	15% 16% 5% 10% 5% 5% 5% 4 5% 6% 25%	8138
	11th to 20th	Night	12% 18% 6% 14% 7% 5% 5% 4 5% 6% 18%	7639
	21st to end	Night	16% 15% 6% 14% 7% 5% 4 3 4 5% 21%	8401
February	1st to 10th	Night	16% 16% 5% 9% 7% 6% 5% 4 5% 5% 23%	2730
	11th to 20th	Night	15% 14% 4 10% 6% 5% 5% 5% 6% 6% 26%	2663
	21st to end	Night	18% 13% 5% 10% 6% 4 6% 3 4 8% 23%	2153
March	1st to 10th	Night	16% 10% 4 8% 7% 5% 4 4 5% 6% 32%	5018
	11th to 20th	Night	13% 9% 3 7% 5% 3 5% 4 5% 8% 37%	5089
	21st to end	Night	18% 10% 3 8% 4 4 3 3 4 6% 37%	5588
April	1st to 10th	Night	19% 11% 4 9% 5% 4 5% 4 5% 6% 30%	2166
	11th to 20th	Night	17% 9% 4 6% 5% 4 5% 3 5% 6% 35%	2004
	21st to end	Night	15% 7% 3 7% 6% 4 5% 4 6% 6% 37%	1890
May	1st to 10th	Night	22% 10% 3 8% 5% 4 4 3 4 5% 32%	4062
	11th to 20th	Night	12% 8% 3 8% 6% 5% 5% 5% 6% 7% 36%	3767
	21st to end	Night	18% 6% 2 5% 4 3 4 3 6% 8% 41%	3926
June	1st to 10th	Night	10% 7% 3 6% 4 4 7% 5% 7% 7% 40%	1600
	11th to 20th	Night	9% 5% 2 6% 4 5% 6% 4 7% 9% 43%	1600
	21st to end	Night	11% 6% 2 5% 5% 4 4 4 5% 7% 46%	1600
July	1st to 10th	Night	7% 5% 2 6% 5% 5% 4 4 5% 10% 47%	3600
	11th to 20th	Night	8% 5% 2 6% 4 4 5% 4 6% 8% 47%	3737
	21st to end	Night	7% 5% 2 6% 4 4 4 4 5% 7% 51%	4428
August	1st to 10th	Night	10% 6% 3 6% 4 4 4 4 6% 9% 44%	2915
	11th to 20th	Night	11% 5% 2 6% 4 4 4 4 6% 8% 44%	2875
	21st to end	Night	7% 4 2 4 4 5% 5% 4 6% 10% 50%	3355
September	1st to 10th	Night	11% 8% 2 5% 5% 4 3 3 5% 7% 47%	2000
	11th to 20th	Night	9% 4 1 5% 3 3 3 3 5% 7% 56%	2151
	21st to end	Night	16% 6% 2 7% 4 4 4 4 5% 7% 39%	2220
October	1st to 10th	Night	14% 7% 3 6% 4 4 4 3 5% 6% 45%	2400
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 4 5% 6% 35%	2400
	21st to end	Night	20% 9% 3 7% 5% 4 4 4 5% 5% 32%	2640
November	1st to 10th	Night	15% 8% 3 6% 4 4 4 4 6% 7% 41%	2672
	11th to 20th	Night	15% 11% 3 8% 5% 4 5% 4 5% 8% 30%	2940
	21st to end	Night	19% 12% 4 8% 5% 5% 5% 4 5% 6% 27%	2940
December	1st to 10th	Night	16% 16% 5% 9% 6% 5% 5% 5% 6% 7% 21%	4720
	11th to 20th	Night	18% 19% 4 9% 5% 4 4 3 4 5% 24%	5348
	21st to end	Night	24% 18% 5% 10% 5% 4 4 3 5% 5% 18%	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	51% 22% 10% 8% 9% 1	4740
	11th to 20th	Day	65% 21% 6% 4 4 1	5280
	21st to end	Day	59% 23% 8% 5% 5%	5780
February	1st to 10th	Day	28% 59% 4 6% 3	1890
	11th to 20th	Day	27% 58% 4 8% 3	1852
	21st to end	Day	24% 60% 4 8% 4 1	1651
March	1st to 10th	Day	42% 28% 10% 12% 7%	5045
	11th to 20th	Day	37% 30% 13% 14% 4 2	5090
	21st to end	Day	41% 30% 5% 16% 8% 1	5586
April	1st to 10th	Day	28% 59% 3 6% 4	2452
	11th to 20th	Day	22% 60% 4 9% 4 1	2581
	21st to end	Day	22% 59% 6% 7% 5% 1	2730
May	1st to 10th	Day	39% 30% 9% 11% 6% 4	5910
	11th to 20th	Day	39% 31% 9% 14% 6%	6128
	21st to end	Day	36% 29% 8% 16% 9% 2	6949
June	1st to 10th	Day	17% 62% 4 8% 7% 1	2800
	11th to 20th	Day	17% 63% 6% 8% 5% 1	2800
	21st to end	Day	15% 61% 5% 11% 8%	2800
July	1st to 10th	Day	29% 25% 10% 22% 13% 1	6290
	11th to 20th	Day	28% 26% 10% 23% 12% 1	6130
	21st to end	Day	24% 26% 12% 21% 17%	6240
August	1st to 10th	Day	30% 37% 10% 14% 9% 1	4221
	11th to 20th	Day	29% 38% 11% 18% 5%	4213
	21st to end	Day	23% 36% 7% 25% 8%	4510
September	1st to 10th	Day	15% 58% 7% 14% 6%	2400
	11th to 20th	Day	12% 58% 5% 15% 9%	2245
	21st to end	Day	18% 58% 8% 11% 5%	2180
October	1st to 10th	Day	19% 36% 11% 20% 13% 1	3260
	11th to 20th	Day	23% 36% 10% 18% 12%	3240
	21st to end	Day	29% 35% 12% 18% 6%	3538
November	1st to 10th	Day	26% 54% 7% 10% 3 1	1840
	11th to 20th	Day	24% 55% 6% 10% 5% 1	1680
	21st to end	Day	29% 55% 8% 5% 3	1680
December	1st to 10th	Day	48% 35% 11% 5% 2	2680
	11th to 20th	Day	44% 32% 8% 7% 8% 1	3066
	21st to end	Day	56% 26% 6% 7% 5%	4048
January	1st to 10th	Night	48% 22% 10% 15% 5%	8138
	11th to 20th	Night	53% 22% 10% 8% 8%	7680
	21st to end	Night	54% 22% 6% 8% 9% 1	8401
February	1st to 10th	Night	25% 59% 6% 7% 3	2730
	11th to 20th	Night	24% 58% 5% 8% 4	2665
	21st to end	Night	25% 59% 4 7% 4	2153
March	1st to 10th	Night	40% 28% 9% 13% 8% 2	5028
	11th to 20th	Night	31% 29% 15% 15% 9% 1	5090
	21st to end	Night	35% 28% 7% 14% 15% 1	5588
April	1st to 10th	Night	26% 59% 3 7% 4 1	2166
	11th to 20th	Night	22% 60% 4 9% 5% 1	2004
	21st to end	Night	18% 59% 5% 10% 6% 1	1890
May	1st to 10th	Night	43% 29% 7% 8% 8% 5%	4069
	11th to 20th	Night	37% 31% 10% 15% 6%	3768
	21st to end	Night	33% 29% 8% 18% 11% 1	3927
June	1st to 10th	Night	17% 63% 3 9% 7% 2	1600
	11th to 20th	Night	15% 62% 5% 11% 6% 1	1600
	21st to end	Night	16% 60% 5% 8% 10% 1	1600
July	1st to 10th	Night	29% 25% 11% 17% 16% 2	3560
	11th to 20th	Night	27% 26% 9% 24% 13% 1	3689
	21st to end	Night	26% 25% 10% 17% 20% 2	4297
August	1st to 10th	Night	25% 36% 10% 17% 11% 2	2904
	11th to 20th	Night	29% 36% 10% 20% 5%	2902
	21st to end	Night	20% 36% 9% 23% 11%	3355
September	1st to 10th	Night	14% 57% 6% 14% 9%	2000
	11th to 20th	Night	11% 57% 6% 16% 10% 1	2151
	21st to end	Night	19% 58% 5% 10% 7% 1	2220
October	1st to 10th	Night	19% 35% 4 20% 20%	3920
	11th to 20th	Night	27% 35% 8% 18% 12%	3899
	21st to end	Night	21% 36% 11% 20% 11%	4252
November	1st to 10th	Night	24% 54% 6% 9% 6% 1	2672
	11th to 20th	Night	23% 55% 6% 11% 5%	2940
	21st to end	Night	28% 55% 8% 7% 3	2940
December	1st to 10th	Night	40% 35% 13% 9% 2	4720
	11th to 20th	Night	44% 31% 6% 9% 9% 1	5348
	21st to end	Night	51% 27% 8% 9% 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	23% 26% 30% 14% 6%	234
	11th to 20th	Day	28% 24% 32% 10% 5% 1	330
	21st to end	Day	24% 21% 35% 15% 5% 1	363
February	1st to 10th	Day	23% 21% 37% 14% 4	330
	11th to 20th	Day	25% 22% 36% 15% 1	330
	21st to end	Day	27% 28% 33% 12%	283
March	1st to 10th	Day	24% 12% 36% 20% 8%	540
	11th to 20th	Day	26% 15% 36% 17% 5% 1	540
	21st to end	Day	30% 12% 32% 19% 7% 1	594
April	1st to 10th	Day	22% 16% 32% 23% 6% 1	540
	11th to 20th	Day	26% 15% 29% 18% 9% 3	532
	21st to end	Day	23% 9% 33% 25% 8% 2	540
May	1st to 10th	Day	23% 10% 30% 25% 8% 5%	507
	11th to 20th	Day	16% 9% 26% 28% 18% 4	527
	21st to end	Day	14% 7% 24% 29% 20% 6%	573
June	1st to 10th	Day	13% 8% 30% 33% 13% 2	530
	11th to 20th	Day	12% 8% 26% 31% 18% 4	530
	21st to end	Day	14% 7% 25% 35% 15% 4	530
July	1st to 10th	Day	8% 6% 20% 31% 27% 8%	525
	11th to 20th	Day	13% 7% 22% 29% 20% 9%	524
	21st to end	Day	8% 4 25% 36% 21% 6%	576
August	1st to 10th	Day	10% 4 19% 31% 24% 11%	526
	11th to 20th	Day	11% 4 22% 31% 20% 11%	519
	21st to end	Day	10% 6% 20% 34% 20% 10%	583
September	1st to 10th	Day	14% 6% 21% 26% 21% 11%	530
	11th to 20th	Day	8% 4 17% 25% 30% 16%	530
	21st to end	Day	17% 9% 25% 27% 15% 7%	530
October	1st to 10th	Day	17% 10% 25% 24% 17% 6%	530
	11th to 20th	Day	20% 14% 33% 24% 8% 2	530
	21st to end	Day	27% 15% 29% 21% 8%	583
November	1st to 10th	Day	20% 20% 34% 18% 6% 3	347
	11th to 20th	Day	24% 23% 27% 18% 6% 2	220
	21st to end	Day	29% 19% 35% 14% 3	220
December	1st to 10th	Day	29% 21% 29% 17% 4 1	220
	11th to 20th	Day	30% 24% 30% 14% 2	220
	21st to end	Day	28% 21% 35% 13% 3	242
January	1st to 10th	Night	24% 16% 38% 17% 5%	840
	11th to 20th	Night	28% 17% 34% 17% 4	840
	21st to end	Night	22% 13% 38% 22% 5%	924
February	1st to 10th	Night	25% 14% 34% 24% 3	840
	11th to 20th	Night	23% 13% 36% 24% 4	823
	21st to end	Night	23% 16% 35% 23% 2	692
March	1st to 10th	Night	20% 12% 34% 27% 7%	840
	11th to 20th	Night	23% 11% 36% 22% 7% 1	840
	21st to end	Night	22% 10% 33% 26% 8% 1	924
April	1st to 10th	Night	22% 12% 34% 28% 4	840
	11th to 20th	Night	22% 10% 31% 27% 10% 1	760
	21st to end	Night	17% 7% 32% 33% 10%	630
May	1st to 10th	Night	21% 5% 27% 29% 15% 2	603
	11th to 20th	Night	15% 4 26% 40% 15% 1	482
	21st to end	Night	13% 6% 22% 35% 21% 2	433
June	1st to 10th	Night	12% 4 29% 40% 15% 1	400
	11th to 20th	Night	13% 3 26% 38% 20%	400
	21st to end	Night	14% 4 21% 43% 19% 1	400
July	1st to 10th	Night	5% 4 21% 43% 26% 2	390
	11th to 20th	Night	9% 4 21% 42% 23% 2	447
	21st to end	Night	10% 2 18% 43% 24% 2	657
August	1st to 10th	Night	7% 4 15% 40% 32% 2	597
	11th to 20th	Night	10% 2 18% 32% 35% 3	594
	21st to end	Night	9% 3 18% 38% 29% 3	740
September	1st to 10th	Night	14% 5% 18% 31% 26% 5%	800
	11th to 20th	Night	12% 3 15% 33% 32% 5%	800
	21st to end	Night	17% 7% 20% 30% 21% 5%	800
October	1st to 10th	Night	16% 8% 26% 28% 19% 3	800
	11th to 20th	Night	22% 11% 30% 27% 9% 2	800
	21st to end	Night	24% 10% 35% 26% 5%	880
November	1st to 10th	Night	20% 12% 31% 26% 11% 1	820
	11th to 20th	Night	22% 15% 33% 22% 8% 1	840
	21st to end	Night	27% 13% 35% 19% 6%	840
December	1st to 10th	Night	29% 17% 31% 18% 6%	840
	11th to 20th	Night	25% 20% 34% 16% 4	840
	21st to end	Night	31% 12% 33% 22% 2	924

Page generated at 2026-04-29 02:21:41. Version ac07

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