Medicine Hat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Medicine Hat clear sky chart from 2005-11-06 to 2026-10-29.

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	8% 7% 3 7% 4 4 5% 4 6% 8% 45%	159399
	Night	8% 8% 3 8% 5% 5% 5% 4 6% 8% 42%	150022
Transparency	Day	37% 6% 15% 27% 13% 3	154008
	Night	40% 6% 15% 25% 12% 2	146424
Seeing	Day	12% 9% 28% 30% 17% 4	18211
	Night	12% 8% 31% 35% 13% 1	27328

By Month

Percentage Cloud Cover SW (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	5% 12% 6% 14% 7% 6% 6% 3 5% 7% 28%	4124
	11th to 20th	Day	5% 10% 5% 10% 4 5% 9% 5% 6% 8% 32%	4140
	21st to end	Day	3 9% 4 8% 6% 5% 4 3 5% 6% 47%	4948
February	1st to 10th	Day	8% 13% 5% 11% 8% 7% 5% 4 5% 6% 28%	1874
	11th to 20th	Day	7% 12% 5% 11% 6% 6% 6% 6% 7% 8% 26%	1845
	21st to end	Day	4 13% 6% 9% 8% 6% 7% 4 6% 8% 31%	1557
March	1st to 10th	Day	5% 9% 4 10% 6% 5% 5% 4 6% 7% 40%	4841
	11th to 20th	Day	6% 8% 4 9% 5% 5% 5% 4 6% 9% 40%	5110
	21st to end	Day	8% 16% 5% 11% 5% 5% 5% 4 7% 9% 26%	5607
April	1st to 10th	Day	8% 10% 3 7% 6% 5% 5% 4 7% 8% 36%	2543
	11th to 20th	Day	10% 12% 4 9% 5% 5% 5% 4 5% 7% 34%	2697
	21st to end	Day	10% 9% 4 9% 6% 4 4 4 5% 7% 37%	2730
May	1st to 10th	Day	11% 8% 2 6% 4 4 4 4 7% 8% 42%	8104
	11th to 20th	Day	13% 7% 3 8% 5% 5% 6% 5% 7% 9% 33%	8377
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 9% 43%	9648
June	1st to 10th	Day	13% 6% 2 7% 4 5% 5% 5% 6% 9% 39%	3150
	11th to 20th	Day	15% 6% 3 6% 5% 4 6% 5% 7% 8% 34%	3150
	21st to end	Day	8% 4 2 4 4 4 5% 5% 7% 8% 48%	3150
July	1st to 10th	Day	7% 2 1 4 3 3 4 3 5% 8% 59%	8819
	11th to 20th	Day	9% 4 2 5% 4 4 4 4 6% 8% 52%	8820
	21st to end	Day	5% 3 1 3 2 2 2 2 4 6% 69%	9575
August	1st to 10th	Day	7% 3 2 5% 4 4 4 4 5% 8% 54%	7842
	11th to 20th	Day	7% 3 2 4 4 4 5% 4 6% 10% 50%	7565
	21st to end	Day	7% 3 1 3 3 2 3 3 4 7% 64%	8374
September	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 4 7% 55%	2576
	11th to 20th	Day	14% 5% 2 4 4 3 4 3 5% 8% 49%	2369
	21st to end	Day	7% 5% 2 5% 3 3 4 3 5% 7% 54%	2310
October	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 8% 9% 48%	3371
	11th to 20th	Day	5% 5% 1 5% 4 5% 5% 3 6% 7% 54%	3350
	21st to end	Day	8% 7% 4 7% 4 4 4 3 4 6% 50%	3232
November	1st to 10th	Day	13% 13% 3 9% 6% 5% 5% 4 5% 6% 31%	1648
	11th to 20th	Day	6% 10% 4 8% 5% 5% 6% 4 5% 8% 39%	1680
	21st to end	Day	7% 13% 3 10% 6% 5% 4 4 6% 8% 33%	1623
December	1st to 10th	Day	8% 16% 4 9% 5% 5% 4 4 5% 7% 32%	2360
	11th to 20th	Day	7% 12% 4 13% 7% 6% 6% 5% 5% 6% 29%	2715
	21st to end	Day	3 9% 3 11% 6% 5% 5% 3 5% 7% 42%	3575
January	1st to 10th	Night	5% 10% 5% 12% 6% 6% 5% 4 6% 9% 32%	8768
	11th to 20th	Night	6% 11% 4 9% 5% 4 5% 4 7% 9% 37%	8820
	21st to end	Night	4 8% 4 10% 5% 5% 5% 4 6% 8% 39%	9279
February	1st to 10th	Night	9% 12% 3 9% 7% 6% 5% 5% 6% 8% 31%	2744
	11th to 20th	Night	6% 11% 4 10% 6% 6% 6% 5% 7% 8% 30%	2662
	21st to end	Night	5% 11% 4 10% 7% 6% 6% 4 6% 8% 35%	2249
March	1st to 10th	Night	4 8% 5% 11% 6% 6% 5% 4 7% 8% 37%	5268
	11th to 20th	Night	7% 7% 3 6% 5% 5% 5% 5% 7% 9% 41%	5110
	21st to end	Night	10% 16% 5% 11% 5% 6% 5% 4 7% 7% 23%	5610
April	1st to 10th	Night	9% 12% 3 9% 5% 5% 5% 4 6% 7% 34%	2073
	11th to 20th	Night	12% 9% 3 8% 5% 4 5% 4 6% 8% 34%	1871
	21st to end	Night	11% 9% 3 9% 4 5% 4 4 5% 9% 37%	1890
May	1st to 10th	Night	16% 8% 2 5% 4 4 4 3 4 6% 44%	4843
	11th to 20th	Night	12% 7% 3 8% 5% 5% 5% 5% 8% 9% 31%	4488
	21st to end	Night	12% 5% 2 6% 5% 5% 5% 4 7% 9% 40%	4525
June	1st to 10th	Night	15% 6% 1 6% 5% 5% 4 4 5% 8% 41%	1470
	11th to 20th	Night	13% 4 2 6% 5% 5% 6% 5% 7% 7% 40%	1470
	21st to end	Night	7% 4 1 5% 3 3 5% 5% 6% 9% 52%	1470
July	1st to 10th	Night	6% 2 1 4 3 3 4 3 6% 8% 60%	4140
	11th to 20th	Night	8% 5% 1 6% 4 4 4 4 6% 9% 49%	4140
	21st to end	Night	6% 2 1 3 3 3 3 3 4 7% 66%	4500
August	1st to 10th	Night	9% 3 2 5% 4 4 4 4 6% 9% 50%	4971
	11th to 20th	Night	9% 4 2 5% 4 4 5% 4 8% 11% 45%	5291
	21st to end	Night	9% 3 1 3 3 2 3 3 5% 7% 62%	5842
September	1st to 10th	Night	9% 4 1 5% 4 4 4 3 6% 7% 54%	2043
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 5% 8% 49%	2247
	21st to end	Night	7% 4 1 5% 3 4 4 3 6% 8% 54%	2310
October	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 6% 8% 51%	4038
	11th to 20th	Night	6% 6% 2 5% 4 4 4 4 6% 9% 50%	4018
	21st to end	Night	7% 7% 3 6% 4 5% 4 3 5% 7% 47%	4710
November	1st to 10th	Night	11% 13% 3 8% 5% 4 4 3 5% 7% 36%	2870
	11th to 20th	Night	6% 11% 3 8% 6% 6% 4 4 6% 7% 39%	2940
	21st to end	Night	5% 13% 5% 9% 5% 5% 4 4 5% 8% 37%	2993
December	1st to 10th	Night	7% 14% 4 10% 6% 6% 6% 5% 5% 7% 31%	5040
	11th to 20th	Night	7% 12% 6% 12% 6% 6% 6% 4 6% 8% 28%	5696
	21st to end	Night	4 8% 4 9% 4 4 5% 4 7% 7% 45%	7623

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	56% 6% 15% 18% 5%	4125
	11th to 20th	Day	49% 5% 16% 17% 11% 2	4140
	21st to end	Day	39% 5% 24% 25% 7%	4948
February	1st to 10th	Day	55% 6% 14% 16% 8% 1	1874
	11th to 20th	Day	51% 8% 13% 19% 8%	1854
	21st to end	Day	50% 6% 13% 22% 9% 1	1557
March	1st to 10th	Day	40% 7% 16% 25% 12%	4841
	11th to 20th	Day	40% 6% 17% 25% 11%	5110
	21st to end	Day	51% 8% 18% 16% 6%	5607
April	1st to 10th	Day	44% 7% 15% 25% 9%	2543
	11th to 20th	Day	49% 5% 12% 25% 8% 1	2700
	21st to end	Day	46% 5% 12% 27% 9% 1	2730
May	1st to 10th	Day	39% 5% 11% 26% 15% 4	8104
	11th to 20th	Day	45% 7% 12% 25% 10% 1	8381
	21st to end	Day	35% 7% 12% 32% 14%	9650
June	1st to 10th	Day	40% 7% 16% 23% 11% 2	3150
	11th to 20th	Day	44% 7% 14% 23% 11% 1	3150
	21st to end	Day	31% 6% 17% 31% 12% 2	3150
July	1st to 10th	Day	24% 5% 16% 28% 21% 5%	8746
	11th to 20th	Day	31% 5% 14% 28% 16% 6%	8739
	21st to end	Day	18% 3 12% 29% 23% 15%	9362
August	1st to 10th	Day	23% 5% 14% 32% 21% 5%	6206
	11th to 20th	Day	29% 7% 19% 34% 10% 1	5964
	21st to end	Day	22% 4 11% 40% 20% 2	6569
September	1st to 10th	Day	31% 4 13% 28% 18% 7%	2576
	11th to 20th	Day	35% 6% 14% 29% 14% 2	2369
	21st to end	Day	29% 5% 14% 31% 17% 3	2310
October	1st to 10th	Day	31% 5% 14% 33% 15% 2	3371
	11th to 20th	Day	29% 4 17% 34% 15% 1	3350
	21st to end	Day	36% 4 10% 37% 12%	3232
November	1st to 10th	Day	53% 7% 14% 18% 7% 2	1648
	11th to 20th	Day	43% 7% 19% 23% 7%	1680
	21st to end	Day	49% 5% 19% 20% 7% 1	1623
December	1st to 10th	Day	51% 6% 22% 17% 4 1	2360
	11th to 20th	Day	54% 8% 19% 17% 3	2714
	21st to end	Day	41% 5% 13% 26% 13% 2	3575
January	1st to 10th	Night	48% 7% 17% 20% 8% 1	8769
	11th to 20th	Night	44% 5% 19% 18% 13% 1	8820
	21st to end	Night	42% 6% 22% 23% 6%	9279
February	1st to 10th	Night	50% 7% 13% 19% 10% 1	2744
	11th to 20th	Night	49% 7% 15% 17% 11% 1	2663
	21st to end	Night	47% 5% 15% 23% 9% 1	2249
March	1st to 10th	Night	42% 8% 18% 21% 11%	5268
	11th to 20th	Night	37% 6% 17% 31% 9%	5110
	21st to end	Night	56% 9% 15% 15% 4 1	5610
April	1st to 10th	Night	48% 4 14% 23% 10% 1	2073
	11th to 20th	Night	46% 6% 11% 23% 13% 2	1871
	21st to end	Night	45% 5% 13% 26% 10% 1	1890
May	1st to 10th	Night	42% 4 7% 27% 15% 5%	4842
	11th to 20th	Night	45% 7% 13% 20% 14%	4489
	21st to end	Night	38% 7% 13% 31% 11% 1	4526
June	1st to 10th	Night	41% 6% 16% 24% 11% 2	1470
	11th to 20th	Night	39% 9% 11% 25% 14% 2	1470
	21st to end	Night	27% 6% 15% 34% 15% 2	1470
July	1st to 10th	Night	21% 5% 16% 32% 21% 5%	4105
	11th to 20th	Night	32% 6% 11% 28% 16% 7%	4098
	21st to end	Night	20% 4 10% 28% 23% 15%	4401
August	1st to 10th	Night	26% 5% 12% 31% 20% 6%	3932
	11th to 20th	Night	34% 6% 19% 28% 11% 2	4168
	21st to end	Night	24% 3 11% 36% 23% 3	4578
September	1st to 10th	Night	29% 7% 12% 27% 19% 8%	2043
	11th to 20th	Night	33% 6% 13% 28% 15% 5%	2247
	21st to end	Night	27% 5% 14% 32% 19% 3	2310
October	1st to 10th	Night	31% 4 12% 35% 16% 1	4038
	11th to 20th	Night	30% 4 15% 32% 17% 2	4018
	21st to end	Night	37% 5% 11% 36% 11%	4710
November	1st to 10th	Night	47% 6% 15% 22% 9% 1	2870
	11th to 20th	Night	44% 6% 20% 20% 9%	2940
	21st to end	Night	46% 5% 23% 18% 7% 1	2993
December	1st to 10th	Night	53% 7% 20% 15% 4	5040
	11th to 20th	Night	52% 7% 23% 14% 3	5697
	21st to end	Night	38% 4 13% 27% 14% 4	7623

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	9% 6% 35% 31% 15% 5%	220
	11th to 20th	Day	12% 8% 39% 27% 14% 1	220
	21st to end	Day	10% 12% 36% 30% 11% 2	242
February	1st to 10th	Day	17% 12% 36% 26% 6% 2	322
	11th to 20th	Day	12% 7% 30% 35% 15% 2	330
	21st to end	Day	9% 10% 33% 34% 13% 3	273
March	1st to 10th	Day	12% 13% 31% 27% 13% 4	525
	11th to 20th	Day	11% 11% 34% 27% 12% 5%	540
	21st to end	Day	12% 13% 31% 27% 15% 2	594
April	1st to 10th	Day	12% 15% 31% 30% 9% 2	540
	11th to 20th	Day	12% 15% 32% 28% 11% 1	532
	21st to end	Day	16% 9% 25% 32% 14% 4	540
May	1st to 10th	Day	15% 9% 24% 28% 18% 5%	711
	11th to 20th	Day	14% 9% 24% 29% 19% 4	775
	21st to end	Day	17% 7% 20% 26% 21% 8%	844
June	1st to 10th	Day	16% 12% 25% 28% 16% 4	780
	11th to 20th	Day	16% 11% 29% 28% 14% 2	780
	21st to end	Day	11% 7% 26% 32% 18% 7%	780
July	1st to 10th	Day	6% 4 22% 37% 25% 5%	771
	11th to 20th	Day	9% 5% 25% 37% 21% 4	768
	21st to end	Day	6% 6% 21% 33% 28% 7%	849
August	1st to 10th	Day	5% 5% 22% 40% 20% 8%	631
	11th to 20th	Day	7% 4 20% 35% 26% 8%	557
	21st to end	Day	7% 9% 23% 28% 26% 7%	627
September	1st to 10th	Day	11% 8% 26% 28% 23% 4	570
	11th to 20th	Day	14% 6% 24% 31% 22% 4	570
	21st to end	Day	11% 10% 32% 31% 12% 4	570
October	1st to 10th	Day	16% 6% 29% 27% 18% 5%	361
	11th to 20th	Day	11% 13% 29% 30% 14% 3	360
	21st to end	Day	17% 11% 35% 24% 12% 1	387
November	1st to 10th	Day	26% 10% 30% 23% 10%	330
	11th to 20th	Day	12% 14% 36% 29% 7% 2	330
	21st to end	Day	12% 10% 38% 25% 10% 5%	300
December	1st to 10th	Day	12% 11% 40% 26% 10% 1	220
	11th to 20th	Day	12% 15% 40% 25% 7%	220
	21st to end	Day	14% 9% 29% 32% 14% 3	242
January	1st to 10th	Night	11% 11% 36% 30% 10% 1	1050
	11th to 20th	Night	13% 10% 36% 31% 9% 1	1050
	21st to end	Night	11% 10% 36% 31% 11% 1	1028
February	1st to 10th	Night	14% 9% 30% 33% 12% 3	840
	11th to 20th	Night	10% 10% 31% 38% 11% 1	824
	21st to end	Night	10% 7% 32% 34% 15% 2	692
March	1st to 10th	Night	9% 7% 34% 37% 11% 2	840
	11th to 20th	Night	12% 11% 33% 32% 11% 1	840
	21st to end	Night	12% 12% 29% 33% 13% 1	924
April	1st to 10th	Night	14% 9% 33% 32% 11% 1	666
	11th to 20th	Night	16% 6% 33% 34% 11%	623
	21st to end	Night	15% 10% 24% 40% 12%	630
May	1st to 10th	Night	15% 7% 23% 35% 18% 2	630
	11th to 20th	Night	13% 7% 26% 34% 19% 1	552
	21st to end	Night	18% 7% 23% 31% 19% 2	455
June	1st to 10th	Night	18% 9% 26% 33% 12% 2	420
	11th to 20th	Night	15% 8% 30% 35% 11%	420
	21st to end	Night	7% 6% 26% 42% 17% 1	420
July	1st to 10th	Night	8% 3 21% 48% 21%	410
	11th to 20th	Night	7% 4 26% 45% 17%	408
	21st to end	Night	4 4 23% 45% 22% 2	460
August	1st to 10th	Night	9% 3 21% 42% 24% 1	585
	11th to 20th	Night	7% 2 21% 43% 25% 1	624
	21st to end	Night	10% 4 25% 38% 22% 1	693
September	1st to 10th	Night	11% 4 26% 42% 15% 1	630
	11th to 20th	Night	14% 5% 21% 41% 18% 1	777
	21st to end	Night	10% 6% 30% 38% 14% 2	840
October	1st to 10th	Night	14% 7% 27% 35% 16%	840
	11th to 20th	Night	15% 8% 31% 33% 12% 2	840
	21st to end	Night	13% 11% 36% 32% 8%	937
November	1st to 10th	Night	17% 11% 35% 29% 7% 1	1025
	11th to 20th	Night	14% 13% 38% 28% 6% 1	1050
	21st to end	Night	11% 10% 37% 33% 8% 1	1050
December	1st to 10th	Night	13% 8% 35% 32% 10% 2	1050
	11th to 20th	Night	11% 11% 38% 28% 10% 1	1050
	21st to end	Night	13% 9% 35% 32% 9% 2	1155

Page generated at 2026-10-26 01:37:51. Version ac07

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