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 2024-01-22.

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% 9% 4 7% 6% 3 5% 5% 6% 7% 33%	74718
	Night	16% 10% 4 7% 6% 3 5% 5% 5% 7% 34%	75209
Transparency	Day	49% 6% 13% 20% 10% 1	74435
	Night	50% 6% 12% 20% 11% 1	75026
Seeing	Day	18% 11% 28% 25% 14% 5%	13382
	Night	20% 9% 29% 28% 13% 1	23008

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	17% 16% 5% 9% 7% 4 5% 6% 4 7% 21%	1540
	11th to 20th	Day	17% 17% 6% 12% 8% 3 4 5% 4 6% 17%	1710
	21st to end	Day	14% 16% 7% 12% 9% 5% 5% 6% 4 6% 16%	1791
February	1st to 10th	Day	18% 18% 5% 11% 8% 5% 4 4 4 4 17%	1620
	11th to 20th	Day	14% 15% 7% 11% 8% 4 5% 5% 5% 4 23%	1573
	21st to end	Day	21% 13% 5% 10% 8% 2 4 4 4 5% 23%	1412
March	1st to 10th	Day	16% 12% 5% 9% 8% 3 4 5% 4 7% 27%	1977
	11th to 20th	Day	14% 14% 5% 7% 7% 3 4 4 4 6% 31%	1980
	21st to end	Day	20% 10% 3 8% 7% 4 5% 4 4 6% 29%	2178
April	1st to 10th	Day	17% 12% 5% 7% 6% 3 4 4 5% 6% 30%	2101
	11th to 20th	Day	18% 9% 4 7% 4 2 4 4 5% 8% 35%	2208
	21st to end	Day	20% 7% 4 6% 6% 3 5% 5% 5% 6% 34%	2340
May	1st to 10th	Day	15% 9% 3 6% 6% 4 5% 5% 5% 7% 35%	2340
	11th to 20th	Day	15% 7% 3 6% 6% 4 5% 4 5% 7% 37%	2396
	21st to end	Day	11% 5% 2 5% 5% 3 5% 5% 6% 9% 44%	2725
June	1st to 10th	Day	12% 6% 3 5% 5% 4 6% 5% 6% 8% 41%	2520
	11th to 20th	Day	11% 6% 3 6% 5% 3 5% 5% 7% 8% 41%	2520
	21st to end	Day	12% 4 2 5% 4 3 4 5% 6% 9% 43%	2520
July	1st to 10th	Day	8% 4 2 4 5% 3 5% 5% 7% 10% 47%	2520
	11th to 20th	Day	11% 6% 2 5% 5% 4 6% 6% 6% 11% 38%	2463
	21st to end	Day	9% 4 2 5% 6% 4 6% 6% 9% 10% 38%	2547
August	1st to 10th	Day	8% 4 2 5% 5% 3 5% 6% 8% 11% 42%	2327
	11th to 20th	Day	9% 5% 2 5% 6% 4 7% 6% 8% 10% 38%	2303
	21st to end	Day	11% 6% 2 5% 6% 4 5% 5% 6% 8% 43%	2484
September	1st to 10th	Day	12% 7% 2 6% 5% 3 4 5% 6% 7% 41%	2160
	11th to 20th	Day	9% 5% 2 4 5% 3 5% 5% 6% 8% 47%	2021
	21st to end	Day	14% 5% 3 6% 5% 3 6% 5% 7% 9% 37%	1962
October	1st to 10th	Day	17% 8% 3 6% 6% 3 5% 5% 4 7% 36%	1800
	11th to 20th	Day	20% 8% 4 7% 8% 4 4 5% 5% 6% 31%	1800
	21st to end	Day	23% 11% 4 8% 6% 4 4 4 5% 7% 24%	1980
November	1st to 10th	Day	14% 7% 3 7% 6% 3 6% 4 6% 8% 36%	1662
	11th to 20th	Day	15% 12% 4 7% 7% 3 5% 5% 5% 8% 30%	1520
	21st to end	Day	22% 14% 3 7% 5% 3 4 4 6% 8% 24%	1520
December	1st to 10th	Day	18% 15% 5% 10% 6% 3 6% 5% 5% 6% 20%	1520
	11th to 20th	Day	20% 14% 5% 8% 5% 4 6% 6% 5% 6% 21%	1906
	21st to end	Day	28% 19% 6% 9% 6% 3 4 4 4 4 12%	2772
January	1st to 10th	Night	18% 14% 6% 9% 8% 4 5% 4 4 5% 23%	2622
	11th to 20th	Night	20% 16% 5% 9% 6% 4 5% 5% 5% 6% 19%	2470
	21st to end	Night	13% 14% 7% 10% 7% 3 5% 5% 5% 6% 24%	2599
February	1st to 10th	Night	18% 16% 5% 8% 7% 4 6% 5% 5% 6% 20%	2340
	11th to 20th	Night	16% 13% 4 9% 7% 4 5% 5% 5% 6% 26%	2273
	21st to end	Night	19% 12% 5% 9% 6% 3 5% 4 4 7% 24%	1843
March	1st to 10th	Night	14% 9% 4 8% 6% 4 6% 5% 5% 7% 32%	1970
	11th to 20th	Night	19% 10% 5% 7% 6% 2 4 5% 4 7% 33%	1979
	21st to end	Night	18% 9% 3 7% 6% 4 4 5% 4 5% 35%	2178
April	1st to 10th	Night	18% 9% 4 7% 5% 3 4 4 5% 6% 32%	1857
	11th to 20th	Night	17% 8% 4 5% 6% 3 5% 4 5% 6% 37%	1715
	21st to end	Night	16% 7% 3 6% 6% 4 5% 4 6% 6% 37%	1620
May	1st to 10th	Night	17% 8% 3 6% 5% 4 4 5% 4 8% 37%	1620
	11th to 20th	Night	14% 4 3 6% 6% 3 5% 6% 6% 6% 41%	1495
	21st to end	Night	11% 6% 2 5% 4 3 4 4 6% 9% 47%	1550
June	1st to 10th	Night	10% 6% 3 5% 5% 4 6% 7% 7% 7% 41%	1440
	11th to 20th	Night	10% 5% 3 5% 5% 4 6% 5% 5% 8% 44%	1440
	21st to end	Night	11% 5% 2 4 6% 3 4 5% 5% 7% 47%	1440
July	1st to 10th	Night	5% 4 2 5% 5% 3 4 5% 4 8% 55%	1440
	11th to 20th	Night	10% 4 2 5% 4 3 4 6% 6% 8% 48%	1493
	21st to end	Night	8% 4 2 5% 5% 3 5% 6% 6% 8% 49%	1771
August	1st to 10th	Night	7% 5% 2 4 5% 3 5% 5% 7% 9% 46%	1611
	11th to 20th	Night	9% 5% 2 5% 4 3 4 6% 6% 9% 47%	1598
	21st to end	Night	8% 4 2 4 4 3 6% 5% 6% 9% 49%	1854
September	1st to 10th	Night	13% 7% 3 4 6% 3 3 4 5% 7% 45%	1800
	11th to 20th	Night	10% 4 2 4 4 2 3 4 5% 7% 54%	1935
	21st to end	Night	15% 6% 3 6% 5% 3 4 5% 5% 8% 41%	1998
October	1st to 10th	Night	15% 7% 3 6% 4 3 4 4 5% 7% 42%	2160
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 5% 5% 6% 34%	2160
	21st to end	Night	22% 10% 3 6% 6% 3 5% 5% 5% 5% 30%	2376
November	1st to 10th	Night	15% 7% 3 5% 4 3 4 5% 6% 7% 41%	2410
	11th to 20th	Night	16% 9% 4 7% 6% 3 5% 5% 5% 9% 30%	2660
	21st to end	Night	19% 11% 4 7% 6% 4 5% 5% 5% 6% 28%	2660
December	1st to 10th	Night	21% 14% 5% 8% 6% 3 5% 5% 5% 6% 22%	2660
	11th to 20th	Night	17% 17% 5% 9% 6% 3 5% 4 5% 6% 23%	3288
	21st to end	Night	28% 18% 6% 8% 6% 3 4 4 4 5% 14%	4884

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	63% 5% 11% 14% 7%	1541
	11th to 20th	Day	69% 5% 10% 13% 3	1710
	21st to end	Day	69% 5% 9% 11% 5%	1791
February	1st to 10th	Day	70% 4 9% 12% 4	1620
	11th to 20th	Day	64% 4 9% 15% 7% 1	1582
	21st to end	Day	63% 5% 9% 15% 7% 1	1412
March	1st to 10th	Day	56% 5% 13% 18% 6% 1	1980
	11th to 20th	Day	54% 5% 10% 19% 10% 2	1980
	21st to end	Day	57% 4 7% 19% 11% 2	2178
April	1st to 10th	Day	54% 5% 11% 18% 12% 1	2101
	11th to 20th	Day	47% 5% 12% 20% 13% 2	2208
	21st to end	Day	50% 6% 11% 19% 12% 2	2340
May	1st to 10th	Day	47% 6% 11% 23% 12% 2	2340
	11th to 20th	Day	46% 6% 13% 21% 13% 2	2400
	21st to end	Day	36% 7% 17% 24% 15% 1	2725
June	1st to 10th	Day	39% 6% 12% 25% 15% 2	2520
	11th to 20th	Day	38% 7% 14% 24% 14% 1	2520
	21st to end	Day	36% 8% 14% 26% 15% 1	2520
July	1st to 10th	Day	31% 8% 13% 27% 19% 3	2450
	11th to 20th	Day	37% 8% 17% 25% 12% 1	2388
	21st to end	Day	37% 9% 15% 23% 13% 1	2405
August	1st to 10th	Day	33% 7% 19% 28% 12% 1	2314
	11th to 20th	Day	37% 8% 18% 26% 10% 1	2303
	21st to end	Day	38% 5% 14% 28% 13% 1	2484
September	1st to 10th	Day	39% 7% 16% 25% 12% 1	2160
	11th to 20th	Day	35% 6% 14% 29% 16% 1	2021
	21st to end	Day	42% 7% 15% 25% 10% 1	1962
October	1st to 10th	Day	49% 5% 14% 19% 12% 1	1800
	11th to 20th	Day	52% 6% 14% 19% 8% 1	1800
	21st to end	Day	61% 5% 12% 16% 6% 1	1980
November	1st to 10th	Day	46% 7% 14% 22% 9% 2	1662
	11th to 20th	Day	53% 7% 15% 16% 10% 1	1520
	21st to end	Day	58% 5% 17% 14% 5%	1520
December	1st to 10th	Day	63% 7% 14% 13% 3	1520
	11th to 20th	Day	63% 6% 15% 10% 5%	1906
	21st to end	Day	77% 5% 8% 8% 2	2772
January	1st to 10th	Night	63% 4 11% 15% 7%	2622
	11th to 20th	Night	66% 6% 12% 11% 4 1	2470
	21st to end	Night	59% 6% 12% 16% 6% 1	2599
February	1st to 10th	Night	64% 5% 12% 13% 5% 1	2340
	11th to 20th	Night	59% 5% 11% 17% 7% 1	2275
	21st to end	Night	60% 5% 11% 16% 7%	1843
March	1st to 10th	Night	52% 6% 11% 21% 9% 2	1980
	11th to 20th	Night	52% 5% 9% 20% 12% 2	1980
	21st to end	Night	50% 5% 7% 21% 14% 3	2178
April	1st to 10th	Night	52% 5% 10% 19% 14% 1	1857
	11th to 20th	Night	49% 5% 8% 20% 16% 3	1715
	21st to end	Night	47% 6% 10% 19% 15% 3	1620
May	1st to 10th	Night	47% 4 10% 22% 14% 4	1620
	11th to 20th	Night	41% 6% 11% 25% 13% 4	1496
	21st to end	Night	34% 6% 13% 26% 18% 3	1551
June	1st to 10th	Night	39% 7% 10% 24% 17% 2	1440
	11th to 20th	Night	37% 6% 12% 25% 18% 2	1440
	21st to end	Night	37% 6% 13% 25% 17% 2	1440
July	1st to 10th	Night	28% 5% 12% 27% 24% 4	1400
	11th to 20th	Night	33% 6% 12% 29% 18% 2	1445
	21st to end	Night	31% 8% 15% 25% 18% 3	1672
August	1st to 10th	Night	31% 7% 16% 30% 14% 2	1600
	11th to 20th	Night	32% 7% 15% 32% 13% 1	1598
	21st to end	Night	32% 6% 14% 29% 16% 2	1854
September	1st to 10th	Night	39% 5% 13% 25% 16% 2	1800
	11th to 20th	Night	30% 6% 11% 35% 18% 1	1935
	21st to end	Night	42% 6% 12% 24% 14% 1	1998
October	1st to 10th	Night	43% 5% 12% 24% 15% 1	2160
	11th to 20th	Night	50% 5% 14% 22% 10% 1	2160
	21st to end	Night	55% 5% 11% 18% 10% 1	2376
November	1st to 10th	Night	41% 6% 13% 25% 13% 1	2410
	11th to 20th	Night	50% 5% 13% 20% 10% 1	2660
	21st to end	Night	56% 5% 18% 16% 5%	2660
December	1st to 10th	Night	62% 6% 14% 14% 4	2660
	11th to 20th	Night	62% 7% 13% 14% 5%	3288
	21st to end	Night	74% 6% 11% 8% 2	4884

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% 23% 30% 16% 7% 1	191
	11th to 20th	Day	26% 21% 36% 11% 5% 1	270
	21st to end	Day	20% 19% 37% 17% 5% 1	267
February	1st to 10th	Day	26% 18% 43% 12% 1	240
	11th to 20th	Day	23% 23% 39% 15%	240
	21st to end	Day	26% 29% 31% 14%	206
March	1st to 10th	Day	22% 13% 34% 23% 8%	420
	11th to 20th	Day	22% 13% 38% 20% 6% 1	420
	21st to end	Day	29% 10% 32% 20% 9% 1	462
April	1st to 10th	Day	19% 15% 33% 25% 7% 1	420
	11th to 20th	Day	25% 13% 29% 20% 10% 4	412
	21st to end	Day	23% 7% 33% 26% 9% 3	420
May	1st to 10th	Day	24% 9% 28% 25% 9% 5%	423
	11th to 20th	Day	16% 8% 25% 30% 18% 4	447
	21st to end	Day	13% 6% 21% 32% 21% 7%	485
June	1st to 10th	Day	13% 6% 29% 36% 14% 2	450
	11th to 20th	Day	14% 7% 24% 32% 20% 4	450
	21st to end	Day	14% 6% 25% 36% 15% 5%	450
July	1st to 10th	Day	7% 4 17% 33% 30% 9%	445
	11th to 20th	Day	13% 4 20% 31% 21% 10%	444
	21st to end	Day	8% 4 24% 37% 22% 5%	488
August	1st to 10th	Day	8% 4 19% 32% 25% 12%	446
	11th to 20th	Day	10% 4 21% 32% 21% 12%	439
	21st to end	Day	11% 5% 19% 34% 21% 11%	495
September	1st to 10th	Day	14% 5% 21% 27% 21% 11%	450
	11th to 20th	Day	9% 4 19% 25% 28% 14%	450
	21st to end	Day	15% 10% 25% 26% 16% 7%	450
October	1st to 10th	Day	19% 11% 24% 22% 18% 6%	450
	11th to 20th	Day	21% 14% 33% 22% 7% 2	450
	21st to end	Day	29% 14% 29% 21% 8%	495
November	1st to 10th	Day	17% 20% 32% 20% 7% 3	289
	11th to 20th	Day	25% 22% 26% 18% 7% 3	180
	21st to end	Day	27% 16% 38% 16% 3 1	180
December	1st to 10th	Day	27% 20% 32% 16% 4 1	180
	11th to 20th	Day	27% 26% 31% 14% 3	180
	21st to end	Day	24% 23% 37% 13% 3	198
January	1st to 10th	Night	25% 15% 37% 17% 6%	760
	11th to 20th	Night	28% 15% 34% 18% 4	760
	21st to end	Night	20% 12% 40% 24% 6%	800
February	1st to 10th	Night	28% 13% 36% 21% 2	720
	11th to 20th	Night	23% 12% 35% 25% 4	703
	21st to end	Night	23% 15% 35% 24% 2	592
March	1st to 10th	Night	19% 11% 35% 28% 8%	720
	11th to 20th	Night	22% 10% 35% 24% 7% 1	720
	21st to end	Night	21% 8% 33% 28% 9% 1	792
April	1st to 10th	Night	21% 10% 33% 31% 5%	720
	11th to 20th	Night	21% 9% 31% 28% 11% 1	651
	21st to end	Night	18% 6% 32% 33% 10%	540
May	1st to 10th	Night	21% 5% 26% 29% 17% 2	540
	11th to 20th	Night	16% 3 26% 40% 15% 1	434
	21st to end	Night	13% 5% 23% 35% 23% 3	389
June	1st to 10th	Night	12% 3 29% 39% 17% 1	360
	11th to 20th	Night	13% 3 25% 38% 21%	360
	21st to end	Night	13% 3 21% 44% 19% 1	360
July	1st to 10th	Night	6% 3 21% 41% 27% 2	350
	11th to 20th	Night	9% 4 21% 41% 23% 2	401
	21st to end	Night	10% 2 19% 43% 23% 3	591
August	1st to 10th	Night	7% 4 14% 40% 33% 2	537
	11th to 20th	Night	10% 2 18% 31% 36% 3	534
	21st to end	Night	9% 3 18% 38% 29% 4	666
September	1st to 10th	Night	15% 5% 17% 32% 25% 6%	720
	11th to 20th	Night	13% 3 16% 32% 30% 5%	720
	21st to end	Night	16% 7% 21% 30% 22% 6%	720
October	1st to 10th	Night	17% 8% 27% 27% 19% 2	720
	11th to 20th	Night	22% 11% 30% 27% 9% 1	720
	21st to end	Night	25% 10% 35% 23% 6%	792
November	1st to 10th	Night	19% 10% 30% 27% 12% 1	740
	11th to 20th	Night	21% 14% 34% 21% 8% 1	760
	21st to end	Night	26% 12% 36% 19% 6%	760
December	1st to 10th	Night	29% 16% 31% 18% 6%	760
	11th to 20th	Night	24% 19% 35% 17% 5%	760
	21st to end	Night	31% 12% 33% 22% 2	836

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